DEVELOPMENTAL CHANGES IN ENCODING AND THE REPRESENTATION OF FACE INFORMATION

Transcription

1 The Pennsylvania State University The Graduate School College of the Liberal Arts DEVELOPMENTAL CHANGES IN ENCODING AND THE REPRESENTATION OF FACE INFORMATION A Dissertation in Psychology by Rebecca J. Von Der Heide c 2011 Rebecca J. Von Der Heide Submitted in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy May 2011

2 The dissertation of Rebecca J. Von Der Heide was reviewed and approved by the following: Michael J. Wenger Professor of Psychology (University of Oklahoma) Co-Chair of Committee Dissertation Co-Adviser Rick O. Gilmore Associate Professor of Psychology Co-Chair of Committee Dissertation Co-Adviser Reginald Adams Assistant Professor of Psychology Peter Molenaar Professor of Human Development Melvin Mark Professor of Psychology Head of the Department of Psychology Signatures are on file in the Graduate School.

3 iii Abstract The question of whether there are developmental changes in the ability to encode face information is the subject of ongoing debate. Two popular hypotheses in the developmental face perception literature arrive at competing conclusions with regard to this question. One line of work in the developmental face perception literature suggests faces are encoded in terms of two independent sources information (a) information about the spatial configuration of the features (b) information about the individual features. This line of work has consistently reported evidence of developmental changes interpreted as differences in encoding these two independent sources of information (Carey & Diamond, 1977; Carey, 1981; Diamond & Carey, 1986). A second line of work in the developmental face perception literature argues that faces are encoded holistically as unitary, perceptual wholes and not in terms of two independent sources of information. This line of work has consistently reported evidence that children and adults both appear to process face information holistically and reports no evidence of developmental changes in encoding (Carey & Diamond, 1994; Cassia et al., 2009; Mondloch et al., 2007; Pellicano & Rhodes, 2003; Pellicano et al., 2006; Tanaka et al., 1998). The purpose of the present study was to test these two competing hypotheses using the theoretical constructs and measures from general recognition theory (Ashby & Townsend, 1986), a multidimensional generalization of uni-dimensional signal detection analyses. Participants (ages 6-22) completed two within-subjects face perception tasks: (a) a composite face task (b) an inversion face task. The pattern of results from both experiments suggested children and adults encoded face information in a qualitatively similar manner. More specifically, both adults and children showed evidence of encoding the dimensions of composite, upright and inverted faces independently rather than holistically at the level of an individual stimulus. There was also evidence of age-related quantitative increases in sensitivity (d ) and decreases in false alarm rates in both face perception experiments. These results are interpreted with respect to developmental changes in encoding face information and the maturation of more general cognitive abilities such as selective attention and response inhibition.

4 iv Table of Contents List of Figures vi List of Tables x Acknowledgments xii Chapter 1. Introduction Developmental Changes in Encoding Face Information Encoding Independent Sources of Face Information Encoding Face Information Holistically Summary Hypotheses Hypothesis Hypothesis Hypothesis Connecting Theory and Data Chapter 2. Experiment Purpose Methods Participants Materials Design and Procedure Results and Discussion Congruency Effect Multidimensional Signal Detection Analyses Developmental Changes in Face Perception Chapter 3. Experiment Purpose Methods Participants Materials Design and Procedure Results and Discussion Inversion Effect Multidimensional Signal Detection Analyses Developmental Changes in Face Perception General Discussion and Conclusions Holistic versus Independent Encoding Connections Between Theory and Data

5 3.4.3 General Cognitive Functioning Conclusions and Future Directions Chapter 4. Appendices References v

6 vi List of Figures 1.1 Schematics of the GRT constructs in their nonviolated and violated configurations. Row A: (i) Perceptual independence (PI) and (ii) a violation of PI. Row B: (i) Perceptual separability (PS) and (ii) a violation of PS. Row C: (i) Decisional separability (DS) and (ii) a violation of DS Experiment 1: Four Primary Types of Stimulus Displays Experiment 1: Schematic representation of GRT predictions for the composite face identification experiment: [a] no violations [b] violation of PS [c] violation of PI [d] violation of DS Experiment 1: Example of the events on a single test trial Experiment 1: The congruency effect for: (a) Children ages 6-17 (b) Adults ages Values to below the diagonal indicate greater sensitivity for congruent compared to incongruent conditions. This ordering would be consistent with the congruency effect frequently reported in composite face experiments Experiment 1: Points on the graph represent values of sensitivity for [a] the bottom part of the composite face at each level (Mike, Paul) collapsed across levels of the top part of the composite face [b] the bottom part of the face at each level (Mike, Paul) collapsed across levels of the top part of the composite face Experiment 1: Points on the graph represent hit rate values for the [a] the bottom part of the composite face at each level (Mike, Paul) collapsed across levels of the top part of the composite face [b] the bottom part of the face at each level (Mike, Paul) collapsed across levels of the top part of the composite face Experiment 1: Points on the graph represent false alarm rate values for the [a] the bottom part of the composite face at each level (Mike, Paul) collapsed across levels of the top part of the composite face [b] the bottom part of the face at each level (Mike, Paul) collapsed across levels of the top part of the composite face Experiment 1: Points on the graph represent values of response bias for the [a] the bottom part of the composite face at each level (Mike, Paul) collapsed across levels of the top part of the composite face [b] the bottom part of the face at each level (Mike, Paul) collapsed across levels of the top part of the composite face Experiment 1: Total number of violations of PS and DS by age

7 2.10 Experiment 1: Measures of marginal sensitivity by age for (a) T x b: a change in the top part of the composite face across levels of the bottom (b) B x t: a change in the bottom part of the composite face across levels of the top. The solid line is the regression line for all observers. The dotted line is the regression line for children (ages 6-15) only. Results of the linear regression analyses are reported in row 1 of Table Experiment 1: Hit rate by age for (a) T x b: a change in the top part of the composite face across levels of the bottom (b) B x t: a change in the bottom part of the composite face across levels of the top. The solid line is the regression line for all observers. The dotted line is the regression line for children (ages 6-15) only. Results of the linear regression analyses are reported in row 4 of Table Experiment 1: False alarm rate by age for (a) T x b: a change in the top part of the composite face across levels of the bottom (b) B x t: a change in the bottom part of the composite face across levels of the top. The solid line is the regression line for all observers. The dotted line is the regression line for children (ages 6-15) only. Results of the linear regression analyses are reported in row 5 of Table Experiment 1: Measures of marginal response bias by age for (a) T x b: a change in the top part of the composite face across levels of the bottom (b) B x t: a change in the bottom part of the composite face across levels of the top.the solid line is the regression line for all observers. The dotted line is the regression line for children (ages 6-15) only. Results of the linear regression analyses are reported in row 2 of Table Experiment 1: Measures of marginal response bias for (a) T x b: a change in the top part of the composite face across levels of the bottom (b) B x t: a change in the bottom part of the composite face across levels of the top. The solid line is the regression line for all observers. The dotted line is the regression line for children (ages 6-15) only. Results of the quadratic regression analyses are reported in row 3 of Table Experiment 2: Types of Stimulus Displays Experiment 2: Schematic representation of GRT predictions for the configuralfeatural inversion experiment: [a] no violations [b] violation of PS [c] violation of PI [d] violation of DS Experiment 2: Events on Each Experimental Trial Experiment 2: The inversion effect (C x f) for: (a) Children ages 6-17 (b) Adults ages Values to below the diagonal indicate greater sensitivity for upright compared to inverted conditions. This ordering would be consistent with the inversion effect frequently reported in previous inversion experiments Experiment 2: The inversion effect (F x c) for: (a) Children ages 6-17 (b) Adults ages Values to below the diagonal indicate greater sensitivity for upright compared to inverted conditions. This ordering would be consistent with the inversion effect frequently reported in previous inversion experiments vii

8 3.6 Experiment 2: Points on the graph represent values of sensitivity in the upright condition for [a] the featural condition at each level (Different, Same) collapsed across levels of the configural change [b] the configural condition at each level (Different, Same) collapsed across levels of the featural change Experiment 2: Points on the graph represent values of sensitivity in the inverted condition for [a] the featural condition at each level (Different, Same) collapsed across levels of the configural condition [b] the configural conditionat each level (Different, Same) collapsed across levels of the featural condition Experiment 2: Points on the graph represent hit rates in the upright condition for [a] the featural condition at each level (Different, Same) collapsed across levels of the configural condition [b] the configural condition at each level (Different, Same) collapsed across levels of the featural condition Experiment 2: Points on the graph represent the hit rates in the inverted condition for [a] the featural condition at each level (Different, Same) collapsed across levels of the configural condition [b] the configural conditionat each level (Different, Same) collapsed across levels of the featural condition Experiment 2: Points on the graph represent false alarm rates in the upright condition for [a] the featural condition at each level (Different, Same) collapsed across levels of the configural condition [b] the configural condition at each level (Different, Same) collapsed across levels of the featural condition Experiment 2: Points on the graph represent false alarm rates in the inverted condition for [a] the featural condition at each level (Different, Same) collapsed across levels of the configural condition [b] the configural condition at each level (Different, Same) collapsed across levels of the featural condition Experiment 2: Points on the graph represent measures of response bias in the upright condition for [a] the featural condition at each level (Different, Same) collapsed across levels of the configural condition [b] the configural condition at each level (Different, Same) collapsed across levels of the featural condition Experiment 2: Points on the graph represent measures of response bias in the inverted condition for [a] the featural condition at each level (Different, Same) collapsed across levels of the configural condition [b] the configural condition at each level (Different, Same) collapsed across levels of the featural condition Experiment 2: Upright Trials: Total number of violations of PS and DS by age Experiment 2: Inverted Trials: Total number of violations of PS and DS by age Experiment 2: Upright Trials: Measures of sensitivity by age for: (a) C x f: a change in configuration across levels of the featural change (b) F x c: a change in facial feature across levels of the configuration Experiment 2: Inverted Trials: Measures of sensitivity by age for: (a) Cxf: a change in configuration across levels of the featural change (b) Fxc: a featural change across levels of a change in configuration Experiment 2: Upright Trials: False alarm rate by age for: (a) Cxf: a change in configuration across levels of the featural change (b) Fxc: a featural change across levels of a change in configuration viii

9 3.19 Experiment 2: Inverted Trials: False alarm rate by age for: (a) Cxf: a change in configuration across levels of the featural change (b) Fxc: a featural change across levels of a change in configuration Experiment 2: Upright Trials: Hit rate by age for: (a) Cxf: a change in configuration across levels of the featural change (b) Fxc: a featural change across levels of a change in configuration Experiment 2: Inverted Trials: Hit rate by age for: (a) Cxf: a change in configuration across levels of the featural change (b) Fxc: a featural change across levels of a change in configuration Experiment 2: Upright Trials: Measures of response bias by age for: (a) Cxf: a change in configuration across levels of the featural change (b) Fxc: a featural change across levels of a change in configuration Experiment 2: Inverted Trials: Measures of response bias by age for: (a) Cxf: a change in configuration across levels of the featural change (b) Fxc: a featural change across levels of a change in configuration Experiment 2: Upright Trials: Measures of response bias by age for: (a) Cxf: a change in configuration across levels of the featural change (b) Fxc: a featural change across levels of a change in configuration Experiment 2: Inverted Trials: Measures of response bias by age for: (a) Cxf: a change in configuration across levels of the featural change (b) Fxc: a featural change across levels of a change in configuration Experiment 1: Morphing: Dimension AB Experiment 1: Morphing: Dimension AC Experiment 1: Morphing: Dimension AD Experiment 1: Morphing: Dimension BC Experiment 1: Morphing: Dimension BD Experiment 1: Morphing: Dimension CD ix

10 x List of Tables 2.1 Experiment 1: Measures of marginal sensitivity (d ) for congruent and incongruent Conditions and 95% confidence intervals calculated using Gourevitch and Galanter (1967) estimators. Note: CI Status indicates whether the 95% confidence intervals for measures of sensitivity overlap (YES) or do not overlap (NO). A reliable difference in marginal sensitivity (*) for the congruent and incongruent conditions is noted for confidence intervals that do not overlap Experiment 1: Logic relating marginal measures of performance to inferences regarding PS and DS. T for the evidence indicates the equality in question held, T for the inference indicates no violation; F for the evidence indicates the equality in question did not hold, F for the evidence indicates a violation.? indicates an uncertain inference Experiment 1: Marginal measures of performance used to guide inferences regarding PI, PS, and DS, considering the relationship between the status (Mike and Paul) of two internal elements of the test stimuli Experiment 1: Composite Face Identification Experiment. Summary of marginal analyses and non-parametric test of sampling independence (SI) for each observer Experiment 1: Regression results and equations for sensitivity (d ), response bias (c), hit rates and false alarm rates Experiment 2: Measures of marginal sensitivity (d ) for upright and inverted conditions for levels of the featural condition collapsed across levels of the configural condition (C x f). The 95% confidence intervals calculated using Gourevitch and Galanter (1967) estimators. Note: CI Status indicates whether the 95% confidence intervals for measures of sensitivity overlap (YES) or do not overlap (NO). A reliable difference in marginal sensitivity (*) for the upright and inverted conditions is noted for confidence intervals that do not overlap Experiment 2: Measures of marginal sensitivity (d ) for upright and inverted conditions for levels of the configural condition collapsed across levels of the featural condition (F x c). The 95% confidence intervals calculated using Gourevitch and Galanter (1967) estimators. Note: CI Status indicates whether the 95% confidence intervals for measures of sensitivity overlap (YES) or do not overlap (NO). A reliable difference in marginal sensitivity (*) for the upright and inverted conditions is noted for confidence intervals that do not overlap Experiment 2: One-way ANOVA tests of the inversion effect at the level of group means Experiment 2: Marginal measures of performance used to guide inferences regarding PI, PS, and DS, considering the relationship between the status (different and same) of two internal elements of the test stimuli

11 3.5 Experiment 2: UPRIGHT FACE ORIENTATION. Summary of marginal analyses and non-parametric test of sampling independence (SI) for each observer Experiment 2: INVERTED FACE ORIENTATION. Summary of marginal analyses and non-parametric test of sampling independence (SI) for each observer Experiment 2: Regression results and equations for sensitivity (d ), response bias (c), hit rates and false alarm rates Demographic information for each observer and the number of trials completed for experiment 1 (Composite Face Experiment) and experiment 2 (Inversion Experiment). Note: ns = A sufficient amount of data was not collected from the participant for analyses or the participant performed at chance levels. The hash mark ( ) indicates the observer did not participate in that experiment xi

12 xii Acknowledgments I would like to express my gratitude to my advisors, Dr. Michael Wenger and Dr. Rick Gilmore. Their guidance, feedback and support provided the foundation for this work. I can not thank them enough for the time and energy they have invested in this project and in my training as a social scientist. I would also like to thank Dr. Reginald Adams and Dr. Peter Molenaar for serving as members of my dissertation committee and their support. I would like to thank Jennifer Bittner and the undergraduate research assistants of the Vision, Memory and Computational Neuroscience Lab that provided support and played a critical role in collecting data for this project, particularly Dan Elbich, Kim Glecos, Phoebe Mathews, Alice Mancino, Brittany Griffin, William Conway, Corbin Emondson, Jennifer Conner and Stuti Patel. I would like to thank the staff members of the Department of Psychology, particularly Sherri Gilliland, who have helped navigate me through the administrative process. I would like to thank my family and friends, particularly my parents, step-parents and brother, for their constant support and encouragement. Finally, I would like my to thank my husband, Brian Patrick Byrne, for his infinite amount of patience, support and faith in my pursuits over the last decade.

13 dedicated to my husband, my parents, and my brother xiii

14 1 Chapter 1 Introduction The human face is a dynamic, content-rich source of visual information. It is the basis for verbal and nonverbal communication and provides a wealth of data that humans use to guide their behavior during social interactions. Adults are extremely good at processing face information. A single glance is enough for them to obtain a vast amount of information about another person s identity, age, race, gender, and emotional state. Adults can use this information to perform a multitude of tasks including the recognition of familiar faces, the discrimination of changes within a face and the discrimination of differences between faces. Researchers have invested a great deal of effort into trying to understand the ability of adults to recognize faces and in trying to determine whether these abilities change with development. One motivation for these investigations are consistent findings that adults perform proficiently on face perception tasks discriminating between and recognizing thousands of faces quickly and accurately, whereas children perform the same tasks more slowly, less accurately and with decreased sensitivity. Interpretations of these findings are inconsistent within the literature. This is often due to the fact that is unclear how differences in performance between adults and children on experimental tasks should be interpreted as developmental changes in the perceptual mechanisms driving face perception. The goal of the present study was to to test if there is a change in the way face information is encoded and represented as a function of development. 1.1 Developmental Changes in Encoding Face Information Two influential hypotheses in the face perception literature pose competing perspectives about the manner in which face information is encoded during perception. The first hypothesis suggests two distinct types of face information are independently encoded during perception (Carey & Diamond, 1977; Diamond & Carey, 1986; Searcy & Bartlett, 1996; Yin, 1970), whereas the second hypothesis, known as the holistic encoding hypothesis, suggests faces are encoded as a perceptual wholes with no explicit recognition of separate parts of the face (Tanaka & Farah, 1993; Tanaka & Sengco, 1997). The contradictory nature of these assumptions is important because they have led to competing conclusions as to whether there are developmental changes in the way face information is encoded during perception.

15 2 The first line of work, which assumes two independent types of face information are encoded during perception, has consistently reported evidence of developmental changes in encoding with specific reference to these two types of information (Carey & Diamond, 1977; Carey, 1981; Diamond & Carey, 1986). By contrast, the second line of work, which assumes each face is encoded as a unitary, holistic entity suggests the ability to encode face information reaches maturity early in life and has found little evidence to suggest changes in encoding occur with development (Carey & Diamond, 1994; Tanaka, Kay, Grinnell, Stansfield & Szechter, 1998) Encoding Independent Sources of Face Information Yin (1969, 1970) was the first to suggest that adults can encode two independent sources of face information during perception. Specifically, he suggested adults can encode face information either (a) as separate features (i.e., encoding the eyes, nose and mouth separately) or (b) as a configuration (i.e., encoding the spatial relationships between the features). He based this conclusion on a pattern of results from a face recognition study of typical adults and patients with damage to the right posterior cortex. In these studies Yin (1969, 1970) presented typical adults and patients with brain damage with upright and inverted images of human faces and objects (e.g., houses, airplanes, other common objects). Participants were asked to indicate if each image in the series was new or if it had been presented earlier in the series. Yin (1969, 1970) found typical adults were significantly more accurate at recognizing previously presented faces when they were in an upright rather than an inverted orientation. Typical adults were also more accurate at recognizing previously presented upright faces than objects in both orientations. Unlike typical adults, patients with brain damage showed no advantage for recognizing upright relative to inverted faces and no advantage for recognizing upright faces compared to upright and inverted objects. Yin (1969, 1970) argued typical adults were more accurate at identifying upright faces because they encoded these faces solely in terms of their spatial configurations and were less accurate at recognizing inverted faces and objects because they were encoded solely in terms of their separate features. He also proposed that patients with right posterior brain damage demonstrated no advantage in accuracy for upright relative to inverted faces because they had lost the ability to encode upright faces in terms of their spatial relationships and could only encode them like objects in terms of their features. Ultimately, Yin (1969, 1970) concluded there are two independent sources of face information available during encoding: (a) information about the facial features (b) information about the spatial configuration of the features.

16 3 Developmental Changes in Independent Encoding The Switch-in-Mode Hypothesis. A critical limitation of Yin s (1969, 1970) studies is that they lack a theoretical or statistical framework that would allow a direct test of the independence or dependence of the two proposed types of face information. He inferred that two sources of information are encoded independently based on the relative difference in behavioral performance of the participants in his task. Unaware of this limitation, early developmental studies of face perception (Carey & Diamond, 1977; Carey, 1981; Diamond & Carey, 1986) adopted Yin s (1969, 1970) framework and the notion that face information is encoded in terms of two independent sources of information. Using a face recognition task similar to Yin s (1969, 1970), Carey and Diamond (1977) reported a pattern of behavioral results for children that appeared to parallel the pattern of results reported by Yin for patients with brain damage. In their study Carey and Diamond (1977) presented adults and children (ages 6, 8, and 10) with upright and inverted images of faces and houses and asked participants to indicate which pictures they had previously seen in the series of pictures. They found children under the age of 10 were equally poor at recognizing faces presented in an upright and inverted orientation, whereas older children and adults showed an advantage in accuracy when faces were presented in an upright orientation. Children under the age of 10 were also more susceptible to errors in recognition than older children and adults when the faces wore disguises (e.g. hats, sunglasses) occluding some of the facial features. Carey and Diamond (1977) suggested children under the age of 10 were less accurate at recognizing upright faces than older children and adults and were more susceptible to errors when features were covered by disguise because they only encoded information about separate features of the face and did not encode information about the spatial configurations of the faces. They also suggested children over the age of 10 and adults were more accurate recognizing upright faces than younger children because they encoded information about the spatial configurations of upright faces rather than information about the separate features. Based on the results of this study, Carey and Diamond (1977) proposed a developmental hypothesis, known as the switch-in-mode hypothesis, which suggests around the age of 10 children switch from encoding face information about separate features of the face to encoding information about their spatial configurations. They suggested the switch from encoding information about the features of the face to encoding information about the spatial relationships of the features around age 10 could be a product of the maturity of the right posterior cortex, a region of the brain research suggests is involved in face perception. As in Yin s (1969, 1970) studies, Carey and Diamond (1977) indirectly inferred that two independent sources of face information are encoded separately via a relative comparison of experimental conditions. They did not use a theoretical or statistical framework that would

17 4 allow a direct test of whether face information was encoded in an independent or dependent manner. This is a critical point because if these two sources of face information are not truly encoded independently, it calls into question the interpretation of developmental change in encoding predicted by Carey and Diamond s (1977) switch-in-mode hypothesis. The Expertise Hypothesis. Carey (1981) subsequently found that children as young as age 4 were significantly more accurate at recognizing faces in an upright orientation. This was evidence against the switch-in-mode hypothesis because according to this hypothesis, children under the age of 10 should encode upright and inverted faces both in terms of their features, which means there should be no effect of inversion on performance. While Carey (1981) continued to rely on the framework that face information could be encoded in two independent ways in order to explain her results, she offered an alternative theoretical account, known as the expertise hypothesis, to explain the developmental differences in performance. The expertise hypothesis proposes that adults and children encode both the information about separate features and information about the configurations of the features during face perception (Diamond & Carey, 1986). However, children become more reliant on information about the spatial relations between features with age because they become more tuned into the nuances of these relations with experience. In sum, this hypothesis asserts that there are two independent types of face information and that both are encoded during perception. It explains these developmental improvements in performance on face perception tasks as a reflection of an increased reliance on information encoded about the spatial relations between features relative to information about the features themselves. As in the studies of Yin (1969, 1970) and Carey Diamond (1977) this study did not use a theoretical or statistical framework that would allow a direct test of whether face information was encoded in an independent or dependent manner. This means the same critical point is relevant in this instance as well; If a direct test of this assumption was to reveal that two sources of face information are not encoded independently, it would call into question the interpretation of developmental change as predicted by the expertise hypothesis Encoding Face Information Holistically The notion that two independent types of face information are encoded during face perception is one popular hypothesis in the face perception literature. Tanaka and Farah (1993) proposed a competing perspective known as the holistic encoding hypothesis. The holistic encoding hypothesis makes two critical assumptions: (a) the elements of a face are dependently encoded and held in memory holistically, as a gestalt or whole object with no explicit recognition of parts of the face; and (b) The features of a face are encoded more dependently or as a whole when they are upright compared to other objects (e.g. inverted or misaligned faces, scrambled faces, houses). Tanaka and Farah (1993) provided initial evidence for the holistic encoding hypothesis

18 5 using an experimental manipulation known as a part-whole task. In this task participants were asked to learn names associated with specific images of upright, inverted or scrambled faces or houses. After learning the name-image associations, participants completed a forced choice recognition task in which a feature from a studied face or object was presented in isolation or in the context of the whole object. For example, if a participant learned a specific face was of a person named Joe they would subsequently be presented with one of Joe s facial features such as his nose (a) in the context of his face (e.g., Joe s nose in Joe s face) (b) in the context of another face (e.g., Joe s nose in Bill s face). Participants would be asked Which is Joe s nose?. Joe s nose and Bill s nose would also be presented in isolation without the context of the face. Participants would be asked Which is Joe s nose?. Tanaka and Farah (1993) hypothesized that if a face is encoded holistically without any explicit recognition of its features, individual features will be recognized more easily when they are presented in the context of a whole face compared to when they are presented in isolation. Additionally, they hypothesized this advantage for recognizing features in the context of the whole object would be bigger for upright faces compared to other types of stimuli (e.g., inverted or misaligned faces, scrambled faces, houses). Tanaka and Farah (1993) reported participants were approximately 10% more accurate and also quicker to respond when features from an upright face were presented in the context of the whole face rather than in isolation. Other types of stimuli (i.e., scrambled faces, inverted faces, houses) did not show an advantage for feature identification in the context of the whole object. The recognition of features for studied upright faces was better when recognition was tested in the context of the whole face and there was additional information available compared to when features were presented in isolation. Tanaka and Farah (1993) interpreted the results of this study as support for the holistic encoding hypothesis and the assumption that upright faces were encoded dependently in a holistic manner. A follow-up study conducted by Tanaka and Sengco (1997) arrived at the same conclusion and also offered support for the holistic encoding hypothesis. In this study participants were also tested on their ability to recognize facial features using a forced choice paradigm. They were asked to study a series of faces and were tested on their ability to recognize features from the studied faces in isolation, in the context of a studied face configuration (i.e., the distance between the eyes was the same for the study and test faces) and in the context of an unstudied facial configuration (i.e., the distance between the eyes was different between the studied and test faces). Participants were (a) most accurate at recognizing features in the context of the studied face configuration and (b) more accurate at recognizing features in the unstudied configuration than recognizing features in isolation. Tanaka and Sengco (1997) interpreted these findings as evidence face information is encoded dependently. Critically, they also argued it was evidence against the independent encoding hypothesis and the suggestion that information about the configuration of facial features and the features

19 6 themselves are encoded as two independent sources of information. They asserted that if information about the spatial relationships between the features and information about the features were truly encoded as independent types of information, participants should have been equally as accurate at recognizing the facial features in the context of the studied and unstudied configurations. The fact participants were more accurate at identifying features when they were presented in the context of the studied face configuration over the unstudied configuration suggested to Tanaka and Farah (1993) that information about the face configuration and the features was encoded dependently. Up until this point, evidence from a specific type of experimental task known as a partwhole task has been reviewed in support for the holistic encoding hypothesis. Results from studies using an alternative experimental manipulation known as the composite face task have also been interpreted as support for the holistic hypothesis (Carey & Diamond, 1994; Goffaux & Rossion, 2006; Hole, 1994; LeGrand, Mondloch, Maurer & Brent, 2004; Michel, Caldara & Rossion, 2006; Richler, Gauthier, Wenger & Palmeri, 2008; Young, Hellawell & Hay, 1987). In the original composite face experiment, Young, Hellawell and Hay (1987) took pictures of famous male faces and divided each face image in half creating a separate top and bottom part from each image. They then mixed the tops and bottoms of the faces and recombined them to form novel faces, which they referred to as composite faces. In their experiment participants were asked to pay attention to the top or bottom of the composite faces and try to identify the famous person. In one condition the tops and bottoms of the composite faces were physically aligned with each other and in another condition the tops and bottoms of the face were physically misaligned with each other (i.e., the top was shifted slightly off to one side and out of alignment with the bottom part of the face). The results of this study showed participants were slower and less accurate at recognizing the top or bottom parts of upright famous faces when the parts of the faces were aligned versus when they were misaligned with each other. Poorer performance in the aligned condition compared to the misaligned condition is known as the composite face effect and is interpreted as evidence for holistic processing. Presumably, adults perform worse when the top and bottom of a face is aligned because they encode faces holistically and are not able to ignore information from the irrelevant part of the face (e.g., when they are asked to make judgments about the top part of the face they can not ignore the bottom part). When faces are misaligned, however, this misalignment presumably stops adults from encoding the top and bottom of the face as a single holistic representation so the identification of the relevant part is not hindered by the additional representation of the irrelevant part of the face. Developmental Changes in Holistic Encoding Several studies have tested children and adults to try to determine whether there are developmental changes in holistic encoding. These studies have used experimental manipulations

20 7 such as the part-whole and composite face tasks with slight modifications to make the manipulations appropriate for testing a broader age range. Developmental studies testing the holistic encoding hypothesis have overwhelmingly concluded that children encode faces in the same manner as adults as holistic, perceptual wholes. For example, Tanaka, Kay, Grinnell, Stansfield and Szechter (1998) asked children ages 6 to 10 to learn the names of four faces. Once children could match the faces to the names without error, they were presented with a forced choice recognition task where they were asked to identify a feature of the face (e.g. Which is Tim s nose?) in the context of a whole face or in isolation. Older children performed better overall than younger children on this task. However, children at all ages recognized features from the studied faces better when they were presented in the context of the whole face rather than in isolation. Tanaka et al. (1998) interpreted this result as evidence that children encode face information in a holistic, dependent manner as young as 6 years. Since the ability to encode face information appeared to be mature by age 6, they further suggested that citing developmental differences in encoding was not a sufficient explanation for differences in performance on face recogintion tasks observed at later points in development. Additional studies have used a part-whole manipulations similar to Tanaka et al s (1998) and composite face tasks to conduct developments test of the holistic encoding hypothesis (Pellicano & Rhodes, 2003; Pellicano, Rhodes & Peters, 2006). These studies also suggest holistic encoding matures early and children as young as age three encode face information like adults, as perceptual wholes (Carey & Diamond, 1994; Cassia, Picozzi, Kuefner, Bricolo & Turati, 2009; Mondloch, Pathman, Maurer, Grand & de Shonen, 2007) Summary The question of whether there are developmental changes in the ability to encode face information is still the subject of ongoing debate. Two popular hypotheses in the developmental face perception literature arrive at competing conclusions with regard to this question. One line of work in the developmental face perception literature suggests face information is encoded as two independent sources of information (a) information about the spatial configuration of the features (b) information about the individual features. This line of work has consistently reported evidence of developmental changes interpreted as differences in encoding these two independent sources of information. A second line of work in the developmental face perception literature argues that faces are encoded holistically as unitary, perceptual wholes and not in terms of two independent sources of information. This line of work has consistently reported evidence that children (as young as age 3) and adults both appear to process face information holistically and reports no evidence of developmental changes in encoding.

21 8 1.2 Hypotheses The preceding review suggests a set of conclusions that motivated the present study. A prevailing question within the developmental literature is whether changes in encoding face information occur across the lifespan. One of the constructs central to most if not all the work considering developmental differences in face processing is the construct of holism. However, the definitions and measures of that construct vary widely and in most if not all cases are defined operationally, at best. The present effort addressed this problem by adopting a set of theoretically-derived representations of holism, and works from each of these representations to specific predictions for a set of empirical measures. Second, the operational definitions of holism are by their nature specific to tasks, making it difficult to understand how the different definitions may or may not be capturing critical, similar, or overlapping aspects of holism and (by extension) relevant developmental changes. The present effort addressed this problem by employing two prominent experimental manipulations composite stimuli and inversion using a common set of stimuli, with all participants exposed to the same stimuli and experimental variations. Finally, there is an imposing level of theoretical diversity in the literature that follows from the variations across operational definitions and tasks. The present effort addressed this problem by abstracting out from the available literature two major classes of hypotheses and, within those two classes, a tractable subset of hypotheses that can be applied across tasks and definitions. I begin by describing the three hypotheses in general terms. For each, I make reference to a set of theoretical constructs relevant to the notion of holism, detailing how each captures the intent of the specific hypotheses. This is followed by a more detailed description of each of the constructs, including both the theoretical definitions and the empirical measures that provide the contact between theory and data Hypothesis 1 An assumption common to the majority of contemporary perspectives on facial perception is that face information is encoded holistically rather than as separate component parts. The present study used three representations of holism derived from general recognition theory (GRT, Ashby Townsend, 1986; O Toole, Wenger, Townsend, 2001 also relevant) to test the hypothesis that children and adults encode faces holistically, as dependent perceptual wholes, rather than as component parts. The three representations of holism derived from general recognition theory (GRT) are referred to as perceptual independence (PI), perceptual separability (PS) and decisional separability (DS). These definitions for holism are applied broadly across experimental tasks allowing them to capture critical, similar, or overlapping aspects of holism and (by extension) relevant developmental changes.

22 9 Predictions A violation of perceptual independence (PI) implies interactions of internal sources of information at the level of an individual stimulus. In the context of a composite face task, a participant would be presented with a pair of face stimuli in which the top and bottom portions of the faces would be clearly delineated (e.g., see Figure 2.1), and would have to indicate whether the top or the bottom halves are the same or different. The modal assumption of holism is generally consistent with a predicted violation of perceptual independence. In general terms, empirical evidence indicating violations of perceptual independence would be strong evidence in favor of a holistic representation. In contrast, a pattern of results indicating no violations in perceptual independence would be evidence against a holistic representation. Critically, if holistic encoding emerges as a function of maturation, then the prediction is that adults should show evidence of violations of PI and children should not. A violation of perceptual separability (PS) implies interactions of perceptual evidence across variations in a dimension of a stimulus. In the context of a composite face task in which the top and bottom portions of facial stimuli are shown with variations in a dimension (e.g. at a high and low levels of contrast), the modal assumption of holism is consistent with a violation of perceptual separability. In contrast, a pattern of results indicating no violations in perceptual separability would be evidence against a holistic representation. If holistic encoding emerges as a function of maturation, then the prediction is that adults should show evidence of violations of PS and children should not. A violation of decisional separability (DS) implies interactions in the decisional criteria used to judge encoded dimensions of a face. In the context of a composite face task in which the top and bottom portions of facial stimuli are shown with variations in a dimension (e.g. the same-different status of the top part of a face), the modal assumption of holism is consistent with a violation of decisional separability. In contrast, a pattern of results indicating no violations in decisional separability would be evidence against a holistic representation. If holistic encoding emerges as a function of maturation, then the prediction is that adults should show evidence of violations of DS and children should not Hypothesis 2 A second general hypothesis in the developmental literature on face perception is that stimulus information can be classified into two general and critically independent sources of information: featural and configural. A second purpose of this proposed effort was to test the assumption that these two sources of information are in fact encoded independently of one another. This was done by way of application of the constructs and measures of GRT.

23 10 Predictions A pattern of results for adults and children that shows no violations in perceptual independence would imply the absence of interactions of internal sources of information and that the dimensions of the face are encoded in an informationally independent manner at the level of a single stimulus. For example, imagine a scenario where a participant had to indicate whether there is a change in configural face information or a change in featural face information. The responses to the changes in these dimensions in a single face stimulus would be considered informationally independent if they are statistically independent. A pattern of results that shows no violations in perceptual independence would be evidence supporting the dual-mode hypothesis and would indicate face dimensions in a single stimulus are encoded independently rather than dependently. A pattern of results for adults and children that shows violations in perceptual independence would be strong evidence against the dual-mode hypothesis and for a holistic representation. This pattern of results would imply informational dependencies in encoding the dimensions of a face at the level a single stimulus. It is at the level of a single stimulus that the dual-mode hypothesis suggests featural and configural face information are encoded as independent sources of information A pattern of results for adults and children that shows no violations in perceptual separability would be evidence supporting the dual-mode hypothesis. It would imply that the encoded dimensions of a face are informationally separate manner another across variations in a stimulus. For example, imagine a scenario in which a face is presented with either featural or configural changes in face information and shown at a low and high level of contrast. Perceptual separability implies that the effect of contrast level at one level of the stimulus (e.g. a change in configural face information) does not depend on the contrast level at the other level of the stimulus (e.g. a change in featural face information). A pattern of results that reveals violations in perceptual separability would provide evidence against the dual-mode hypothesis. It would suggest that configural and featural face information are encoded dependently across all levels of the stimulus. A pattern of results for adults and children that shows no violations in decisional separability would be evidence supporting the dual-mode hypothesis. It would indicate the decisional criterion used to judge one encoded dimension of the face is independent of the decisional criterion for the other face. In the case of decisional separability the decisional criterion used to judge one encoded dimension of the face (e.g. criterion for judging a change in configural information) would not vary across levels of the decisional criterion for the other face dimension (e.g. criterion for judging a change in featural information). A pattern of results for children and adults indicating violations in decisional separability would be evidence against the dual-mode hypothesis and would imply the criterion to judge one encoded face dimension (e.g. criterion for judging a change in configural information)

24 varies across levels of the other encoded face dimension (e.g. criterion for judging a change in featural information) Hypothesis 3 A third general assumption in the literature is that children are generally slower and less accurate on face perception and recognition tasks. According to this assumption, there are no qualitative differences between children and adults in processing and representation. Children simply do what adults do more slowly and less accurately, and their performance simply improves quantitatively with age. Predictions Age-related incremental improvements in overall speed (decreases in mean RT), overall accuracy (increases in mean accuracy) and sensitivity (increases in d prime) on face perception tasks would be evidence supporting a quantitative change in encoding and/or processing face information with development. 1.3 Connecting Theory and Data Overview of GRT Measures General recognition theory (Ashby & Townsend, 1986) is a multi-dimensional generalization of signal detection theory (Green & Swets, 1966). It provides a language to precisely define terminology and make predictions for holistic encoding at the levels of perceptual and decisional dependencies among the dimensions of a stimulus. Both perceptual and decisional dependencies can be used to represent hypotheses regarding holisms (a) as violations of perceptual independence (b) as violations of perceptual separability (c) as violations of decisional separability. The present study used these three GRT representations of holistic encoding to test the hypothesis that children and adults encode faces holistically, as dependent perceptual wholes, rather than as component parts. Perceptual Independence Perceptual independence (PI) implies the perceptual effect of one dimension of an individual stimulus is independent of the perceptual effect of another dimension of that stimulus. A violation in perceptual independence implies the two dimensions of a single stimulus are dependent. In order to illustrate the concept of perceptual independence imagine an experiment in which participants are presented with an image of a human face followed sequentially by the image of a second face. They are then asked to make one of four possible

25 response choices indicating whether: (a) the top and bottom of the first and second face are the same (b) the top of the face of the second face is the same as the first, but the bottom of the face is different (c) the top of the face is different from the first, but the bottom is different (d) the top and the bottom of the first and second faces are the same. Assuming stimuli are repeatedly presented for all four conditions (i.e. a d above), participants would encode perceptual evidence variably across trials, with that variability characterized as a bivariate random variable. As result, there would be four bivariate distributions of encoded evidence, each assumed bivariate Gaussian and each assumed to represent the interaction at a level of two stimulus dimensions (see Figure 2.9 ). Each distribution is parameterized by two means (expressed as a mean vector) µ = [ µ T µ B ], two variances, and a correlation parameter (expressed as a covariance matrix) Σ = [ σ 2 T ρσ T σ B ρσ T σ B σ 2 B ], The subscripts T and B index the parameters for the marginal distributions for the top and bottom features, respectively. Responses are parameterized by a slope and intercept parameter using continuous- or piecewise-linear decision bounds. Continuous linear bounds are parameterized by a slope and intercept parameter is intercept for each dimension (λ T and λ B ). Piecewise linear bounds are parameterized by a single location parameter for each bound. Figure 2.9 shows an example of the bivariate distributions in GRT space when perceptual independence is preserved versus conditions when there is a violation of perceptual independence. Perceptual independence is preserved when the correlation parameter σ in the covariance matrix is equal to 0; non-zero correlations represent a violation of PI. In that case, 12 f i,j (t, b) = g i (t)g j (t), where t and b are the random variables representing the encoded information about the relative state of the top and bottom of the test stimulus, respectively, the subscripts i and j indicate the specific state of those two components (same, different) relative to the standard, f() is the joint distribution of evidence, and g(t) and g(b) are the two marginal distributions. A violation in perceptual independence has been suggested (e.g., O Toole, Wenger, Townsend, 2001) to represent the strongest form of perceptual holism. It

26 suggests that perceptual dependencies exist at the level of an individual stimulus. 13 Perceptual Separability Perceptual Separability (PS) represents the idea that the perceptual evidence for one dimension does not vary across the levels of the other dimension. A violation in perceptual separability indicates the perceptual evidence for one dimension of a stimulus changes across levels of the other dimension. Figure 2.9 shows the contours for the distributions of perceptual evidence in GRT space when perceptual separability is preserved versus conditions when there is a violation in perceptual separability. Perceptual separability is said to hold if perceptual evidence for the bottom part of the face is not altered by the same-different status of the top part of the face: g i (t) = g j (t), (1.1) where g i (t) and g j (t) are the marginal distributions of the evidence regarding the relative state of the top feature at two levels (e.g., same and different), with there being a similar equality for the relative state of the bottom of the face. A violation of perceptual separability would suggest that the perceptual evidence for one dimension varies across levels of the other dimension. For example, perceptual evidence that the bottom of the face is the same could be greater when the top of the face is the same compared to when the top of the face is different. A violation in perceptual separability would be evidence of holistic encoding in the sense that the perceptual evidence for one dimension of a stimulus is dependent on the levels of the other dimension. Unlike violations in perceptual independence, this would be evidence for holistic encoding across repeated presentations of the stimulus rather than at the level of an individual stimulus. Decisional Separability The construct of decisional separability refers to the response criteria for two dimensions of the stimulus. Decisional separability is said to hold if participants use the same criterion for any one dimension across the two levels of the other dimension. Decisional separability is violated if this criterion varies across two dimensions of the stimulus. For example, decisional separability would be violated if the criteria for judging the top part of a composite face as different varied from the criterion used to judge the top part of the composite face as the same. Figure 2.9 shows the contours for the distributions of perceptual evidence in GRT space when decisional separability is preserved (i.e. when the decision bound at one dimension is unaffected at a level of the other dimension) versus conditions when there is

27 14 a violation in decisional separability. Assuming the decision bounds are linear they will be parallel to the axes when there is no violation in decisional separability. A violation in decisional separability would be evidence of holistic encoding in the decisional criteria used to make judgments about the encoded dimensions of the face across repeated presentations of the stimuli. Figure 1.1: Schematics of the GRT constructs in their nonviolated and violated configurations. Row A: (i) Perceptual independence (PI) and (ii) a violation of PI. Row B: (i) Perceptual separability (PS) and (ii) a violation of PS. Row C: (i) Decisional separability (DS) and (ii) a violation of DS.

28 15 Quantitative Improvements in Performance Several developmental studies have reported evidence of a quantitative change in face perception with development. For example, Itier and Taylor (2004) reported a steady improvement in face recognition with age using accuracy, reaction time and d scores. They proposed that children process faces in the same manner as adults, but do so less efficiently. They also reasoned their pattern of results and the pattern of results in the study by Flin (1985) provided data supporting this explanation because they calculated measures of sensitivity (d ) in addition to the measures of accuracy and reaction time that were reported by other studies. It was these measures of d that showed a gradual increase in the sensitivity to recognize upright and inverted faces with age and led to their suggestion that there was a steady quantitative change in the ability to process faces with age. In accordance with Itier and Taylor (2004) measures of sensitivity (d ) will be assessed in the present experiment for evidence of age-related changes in face perception. In addition measures of response (c), hit rates, and false alarm rates will also be assessed for age related changes. Significant increases in (d ) scores with age would be of evidence of improvements in sensitivity and the ability to discriminate face information with development, whereas a decrease in these values would indicate that sensitivity and the ability to discriminate face information gets worse with age. Significant age-related increases in response bias measures (c) from negative to positive values would indicate that judgments on face information become more conservative with age, whereas significant decreases in these values from positive to negative values would indicate that judgments become more liberal with age. A significant age-related increase in hit rates would indicate improvements in correctly identifying face information, whereas a decrease in these rates would indicate that the ability to correctly identify face information gets worse with age. An age-related increase in false alarm rates would indicate an increasing likelihood of identifying targeted face information as being present when it is not, whereas a decrease would indicate a decreasing likelihood of identifying targeted face information as being present when it is not.

29 16 Chapter 2 Experiment Purpose The purpose of the first experiment was to (a) provide a test of the hypothesis that adults encode and represent face information holistically (b) test whether there are developmental changes in encoding face information. 2.2 Methods Participants Eleven adults and 17 children participated in this experiment. Six adults and nine children were female and five adults and eight children were male. The adult participant group was comprised of Penn State undergraduate students and individuals ages recruited from local internet and bulletin board advertisements. Children ages 5-17 were also recruited via local internet and bulletin board advertisements. All participants had normal to correctedto-normal vision and unencumbered use of both hands. All participants were right-handed except for except for one adult and one child. None of the participants were diagnosed with a language, hearing, visual, neurological, developmental or psychiatric disorder. Adults and children were paid $8 per hour for their participation. Children were also given the opportunity to select a small gift from a prize box Materials Photographs were taken of two Caucasian males enrolled in the undergraduate psychology program at the Pennsylvania State University. Models wore a surgical cap and scrubs in order to hide their hair and clothing. Images of their faces were presented inside an oval surrounded by a 50% gray background (RGB value 149). This composite face stimuli were presented in an oval in order to replicate other researchers and to eliminate cues derived from the shape of the head or chin. The two face images of the male models were first cut in half to produce two face tops and two face bottoms (192 x 217 pixels). Images were sized at 4.76 cm (v) 2.59 cm (h). When viewed at a fixed distance of 76 cm, the images

30 17 subtended 3.58 (vertically) and 1.95 (horizontally). Face tops and bottoms were combined to produce a base set of four stimuli (see Figure 2.1). Stimuli were also morphed along each dimension using Abrasoft Fantamorph software (see Figures ), which resulted in a total of 60 face images. The purpose of morphing was to increase the difficulty of the task and induce errors in person identification. A thin white line that was 2 pixels thick and 50% opaque separated the top and bottom part of the face. Each of the 60 stimulus images presented with equal frequency, but in a random order during the experiment. Figure 2.1: Experiment 1: Four Primary Types of Stimulus Displays Design and Procedure The experiment was conducted as a 2 (top face part: Mike or Paul) 2 (bottom face part: Mike or Paul) factorial design. A schematic representation of the factorial is presented in Figure 2.2 in the context of GRT predictions for the present experiment. Adult participants began each session with five minutes of dark adaptation. The door to the testing room was kept partially open during testing sessions with children so they could be monitored during the task. Although children were not adapted to the dark by conventional standards (i.e. in a dark room with the door closed), the door was closed 3/4 of the way, the lights were turned off in the testing room and the laboratory during sessions. Participants were seated at a viewing distance of approximately 76 cm from the computer monitor. Adults used a chin rest to maintain head position; children were not required to use a chin rest. Children were also provided with an opportunity to pick out a sticker as a reward for completing each section of the experiment. Participants completed as many trials as possible in a single 90 minute session and had an unlimited amount of time to make each of two responses on each trial. The number of trials participants were able to complete for Experiment 1 had a wide range between 247 trials to 1576 trials. Adults completed more trials in a single session than children. This is primarily because children took longer to respond on each trial and took more breaks thank adults from the experiment during the 90 minute testing

31 session. Table 4.1 provides information about the specific number of trials each participant was able to complete for Experiment Identity Learning Phase After dark adaptation, each participant completed a learning phase during which they were presented with two photographs of the male models side by side on the computer screen. Each face was labeled with an imaginary name that was clearly presented in 18 point font below each of the face images. For the purpose of this experiment one model was given the imaginary name Mike and the other model was given the imaginary name Paul. The experimenter taught each participant the identity of the two male models by pointing to the center of the computer screen and asking the participant to follow her finger. She then pointed to one of the face images on the computer screen and said This is a man named Mike. Please take a very close look at Mike s face. We will ask you to describe his face after taking a close look. After the participant examined the face for approximately five seconds, the experimenter covered the computer screen asked the participant to describe Mike s face. This was to confirm that children and adult participants were paying attention during the learning face and processing information about the face image. The experimenter thanked the participant for his or her description of the face image and then pointed to the second face image and said This is a man named Paul. Please take a close look at Paul s face. We will ask you to describe his face after taking a close look. After approximately 5 seconds, the experimenter covered the computer screen and asked the participant to describe Mike s face. The experimenter thanked the participant for his or her description of Paul s face and then the experimenter covered the names under both face images and asked the participant to name each of the faces. Once the participant correctly identified one face image as Mike and the other face image as Paul, participants were asked to complete a short block of practice trials. Identification Practice Participants were presented with a short block of practice trials consisting of four face images presented in a random order (i.e., two unaltered images of Paul and two unaltered images of Mike). All four face images presented during the practice were either Mike or Paul. None of the images were combined composites of the two identities. The purpose of this practice block was to ensure the participants could identify Mike and Paul. This practice was repeated until participants could complete the practice with 100% accuracy.

32 Figure 2.2: Experiment 1: Schematic representation of GRT predictions for the composite face identification experiment: [a] no violations [b] violation of PS [c] violation of PI [d] violation of DS. 19

33 20 Composite Face Task Practice Participants were randomly presented with 10 Mike-Paul composite faces. They were initially cued to the top or bottom part of the face by an asterisk that appeared above the top part or below the bottom part of the image. Each participant was instructed to Press the [ z ] button on the keyboard if they thought the cued part (top or bottom) of the face was Mike and to Press the [ / ] button when they thought the cued part of the face was Paul. Participants were allowed to proceed to the test trials if they completed the practice with at least 70% accuracy. Figure 2.3 shows an example of a single test trial participants completed during the task practice and the test portion of the session. Figure 2.3: Experiment 1: Example of the events on a single test trial. Test Trials Stimulus images were presented on a computer monitor measuring 45 cm on the diagonal at a resolution of pixels. Participants were told they could take a break from the experiment at any point in time. Each trial was self-initiated and began with a small black dot on the screen. When the participant was ready to begin a trial, they pressed a button on the keyboard. A fixation cross was presented with a random fore-period and a uniform distribution ranging from 300 to 700 ms. The offset of the fixation cross was followed by a 100 ms presentation of a blank screen and then the presentation of the test stimuli. A test face appeared on the screen and the participant was asked to make two sequential responses. First, the participant was cued by an asterisk above the top or below the bottom part of the face. The participant was instructed to press the [ z ] button if the cued part of the face was Mike and the [ / ] button if they thought the cued part was Paul. After the first response, the test stimulus remained on the computer screen and the

34 21 asterisk moved above or below the previously uncued part of the face. The participant was asked to make a second response indicating whether they thought this part of the face was Mike or Paul. The stimulus image was followed by a blank mid-gray screen for ms. In order to make the experimental task more engaging for the children, the experiment was presented in the context of a board game. Adult and child participants were told that after completing each block of trials, their game piece would advance along the game board. Each participant was instructed that it was important to try to be as accurate as possible and to respond as quickly as possible while completing the task. Participants were not presented with feedback. A complete identification task is most often used to obtain the data necessary for multi-dimensional signal detection analyses. In this type of task every dimension of a test stimulus (e.g. Mike-Mike, Mike-Paul, Paul-Mike, Paul-Paul) is paired with a unique response (e.g. keyboard buttons [ z ], [ x ], [. ], [ / ] ). An alternative task known as the sequential response task was used in this case to obtain the necessary data for GRT analyses. This was to limit the number of possible responses children would need to learn in order to successfully complete the task. The concern was that more than two responses would make the task too difficult for children to complete. Richler et al. (2008) provided evidence that both types of experimental tasks can lead to similar patterns of GRT results and inferences from GRT measures in the context of a composite face task. 2.3 Results and Discussion Data from the composite face experiment was evaluated in reference to three questions: (a) Did the stimuli used in the present study replicate the congruency effect reported in other composite face studies? (b) Were there violations in PI, PS and/or DS and did these violations change with age? (c) Was there evidence of developmental changes in the ability to encode face information? A criterion(α) of 0.05 was used to infer statistical reliability in all cases Congruency Effect The first goal of the present study was to analyze the data for evidence of the congruency effect in order to replicate previous composite face studies. Several composite face experiments have reported greater accuracy and/or sensitivity (d ) when the top and bottom parts of the composite face are congruent and elicit the same response (e.g., top and bottom parts of the composite face are Mike ) versus when the parts of the composite face are incongruent and elicit different responses (e.g., top part of the composite face is Mike and bottom part is Paul ). Researchers have interpreted this congruency effect as evidence of a failure of selective attention and an indicator of holistic processing (Richler et al., 2008, 2009). Mean values for measures of sensitivity (d ) and the 95% confidence intervals for these mea-

35 22 sures were calculated for all observers in the congruent and incongruent conditions and are presented in Figure 2.4 and Table 2.1. Confidence intervals for measures of marginal sensitivity were calculated according to Gourevitch and Galanter (1967). The diagonal line in Figure 2.4 represents equality for values of sensitivity in the congruent and incongruent conditions; points above the line represent mean measures of sensitivity that were higher in the incongruent versus the congruent condition, whereas points below the line represent mean measures of sensitivity that were higher in the congruent versus incongruent condition. Points in Figure 2.4 generally fell below the diagonal line suggesting a trend for greater sensitivity in the congruent condition. The column labeled CI Status in Table 2.1 lists the status of the confidence intervals for the congruent and incongruent conditions indicating if they did or did not overlap. Confidence intervals did not overlap for 3 of the 15 children and 1 of the 11 adult observers indicating these observers were significantly more sensitive in the congruent versus the incongruent condition. Differences in the congruent and incongruent conditions were also tested across participants at the level of the group mean. A one-way ANOVA was used to test for a difference in marginal sensitivity (d ) between the congruent and incongruent composite face conditions for all observers. The results indicated that marginal sensitivity for the congruent condition (M = 1.59, SD =.33) did not significantly differ from incongruent condition (M = 1.50, SD =.39), F (1, 50) =.79, p =.38. A one-way ANOVA was also performed separately for children and adults. The primary reason a 2 (children, adults) x 2 (congruent, incongruent) ANOVA was not performed is because there were an unequal number of observers in each group (17 children and 11 adults). There were no significant differences in marginal sensitivity between the congruent (M = 1.54, SD =.34) and incongruent (M = 1.43, SD =.41) composite face conditions for children, F (1, 28) =.78, p =.38. There were also no significant differences in marginal sensitivity between the congruent (M = 1.64, SD =.35) and incongruent (M = 1.59, SD =.37) composite face conditions for adults, F (1, 20) =.10, p =.75. Participants in the present study showed a trend for performing with greater sensitivity in the congruent versus the incongruent condition. However, there was only evidence of a significant difference in this direction for 4 of the 27 observers. Contrary to previous composite face studies, the congruent and incongruent conditions were not significantly different at the level of the group mean when data were analyzed for all observers or separately for children and adults. The difference in sensitivity for the congruent and incongruent conditions was smaller in the current study compared to other composite face studies reporting the congruency effect. This appears to be the result of greater sensitivity in the incongruent condition in the present study. For example, Richler et al. (2008) reported a range of values for sensitivity of d = 1.0 d = 1.3 for congruent conditions and a range of values for sensitivity of d =.40 d =.80 for incongruent conditions. The values for sensitivity in the

36 Figure 2.4: Experiment 1: The congruency effect for: (a) Children ages 6-17 (b) Adults ages Values to below the diagonal indicate greater sensitivity for congruent compared to incongruent conditions. This ordering would be consistent with the congruency effect frequently reported in composite face experiments. 23

37 Table 2.1: Experiment 1: Measures of marginal sensitivity (d ) for congruent and incongruent Conditions and 95% confidence intervals calculated using Gourevitch and Galanter (1967) estimators. Note: CI Status indicates whether the 95% confidence intervals for measures of sensitivity overlap (YES) or do not overlap (NO). A reliable difference in marginal sensitivity (*) for the congruent and incongruent conditions is noted for confidence intervals that do not overlap. Congruent (95% CI) Incongruent (95% CI) Group Observer Age Congruent (d ) Incongruent (d ) Lower Bound Upper Bound Lower Bound Upper Bound CI Status Children *NO YES YES *NO YES YES YES YES YES YES *NO YES YES YES YES Adults *NO YES YES YES YES YES YES YES YES YES YES 24

38 25 incongruent condition were higher for observers in the present experiment. This difference could be due to the limited stimulus set and a greater repetition of stimuli in the present study. The present study used a smaller set of composite face stimuli than other composite face studies. For example, Richler et al. (2008) constructed composite faces from 200 different faces to use in a composite face same-different task, whereas the present study constructed composite stimuli from only two faces. As a result of the limited stimulus set, the incongruent condition could have been more salient in the present study resulting in higher sensitivity in the incongruent condition and a smaller difference between the congruent and incongruent conditions. The stimulus set in the present experiment was limited to a small number of face images in order to allow participants to learn the identify of two specific people (i.e., Mike and Paul) and perform an identification task. By comparison, participants in other composite face studies were asked to complete a same-different task, which required them to make a more general response indicating whether the top or bottom parts of paired composite faces were the same or different. A greater number of composite face stimuli can be used in a same-different task because participants do not need to memorize and associate each face stimulus with a specific identity in order to successfully perform the task. Using a large number of composite faces in the present study was not feasible in the context of an identification task because it would have required participants to learn a large number of identities. Pilot work demonstrated that using a larger number of stimuli made the identification task significantly more difficult for adults to perform with many participants performing at chance levels Multidimensional Signal Detection Analyses The second goal of this experiment was to evaluate evidence for holistic encoding using the statistical measures and logical inferences provided by general recognition theory. Statistical evidence was analyzed and inferences with respect to possible violations of PI, PS, and DS. A schematic representation of the four GRT models used to demonstrate predictions for the composite face task are presented in Figure 2.2. In order to draw inferences about violations in PI, PS, and DS each observer s performance was first summarized in a 4 (each stimulus state) row 4 (each possible response) column matrix. The distribution of response frequencies in each observer s matrix were tested using a set of equalities that were first developed by Ashby and Townsend (1986) and have been shown to hold under the assumptions of PI, PS, and DS (Ashby & Townsend, 1986; Kadlec, 1999, 1992; Kadlec & Townsend, 1992). Table 2.2 provides a summary of the estimates and equalities as they relate to the inferential logic initially developed by (Ashby & Townsend, 1986; Kadlec, 1992). The question marks noted in Table 2.2 represent instances in which the evidence from

39 Table 2.2: Experiment 1: Logic relating marginal measures of performance to inferences regarding PS and DS. T for the evidence indicates the equality in question held, T for the inference indicates no violation; F for the evidence indicates the equality in question did not hold, F for the evidence indicates a violation.? indicates an uncertain inference. Evidence Inference MRI? Equal marginal d Equal marginal c PS DS T T T T T T T F T F T F T F T T F F F F F T T T? F T F T F F F T F? F F F F? 26 marginal measures that suggests DS holds is uncertain subsequently making any inferences predicated on DS holding uncertain as well. This issue in the inferential logic was first noted by Ashby and Townsend (1986). One approach for resolving these uncertainties is to use a procedure outlined by Thomas (2001) for fitting fully-specified multivariate gaussian models to the identification-confusion matrices. These models have not yet been fit to the identification-confusion matrices in the present study, but will be in the future in order to resolve the uncertainties in the data. Table 2.3 provides a list of the marginal measures of performance used to make inferences about the status of PI, PS and DS (i.e. whether equality holds or the construct is violated) for the present experiment. Non-parametric tests of sampling independence were also used in order to further clarify inferences regarding violations in PI. Although these measures have been used in previous studies of the composite face effect (Richler et al., 2008), this is the first study to use them to examine developmental differences in face perception. The results from the comparisons of the marginal measures and inferences based on evidence from these measures regarding each of the GRT constructs (i.e. PI, PS, DS) are summarized in Table 2.4. Inferences Regarding PI, PS, and DS According to the holistic encoding hypothesis, holism occurs at the level of representation of an individual face. More specifically, this hypothesis suggests that each face is encoded and represented as a unitary, perceptual whole. Evidence that holism occurs at the level of the representation of an individual face would be the finding of violations of perceptual independence. As Table 2.4 documents, there were no violations of PI suggested for any of the observers in any of the conditions. Contrary to predictions made by the holistic encoding hypothesis, these results suggest observers represent the dimensions of the individual composite face stimuli in an independent manner.

40 27 Table 2.3: Experiment 1: Marginal measures of performance used to guide inferences regarding PI, PS, and DS, considering the relationship between the status (Mike and Paul) of two internal elements of the test stimuli. Quantity P (a M b i A M B i) P (a M b i A P B i) d (A, B i) c(a, B i) MRI SI Definition and description marginal probability of correctly identifying the top part of the face as being Mike ( hit ) when the state of the top part of the face is i (Mike, Paul) marginal probability of incorrectly identifying the top part of the face as being Mike ( false alarm ) when the state of the bottom part of the face is i(mike, Paul) marginal sensitivity to the correct state of the of the top part of the face when the bottom part of the face is in state i (Mike, Paul) = 1 2 {z[p (a M b i A M B i)] z[p (a M b i A P B i)]} marginal criterion for reporting the configuration as Mike when the state of the lips is i (Mike, Paul) = 1 2 {z[p (am bi AM Bi)] + z[p (am bi AP Bi)]} 2 non-parametric equality testing for the presence of marginal response invariance, pertinent to inferences regarding PS and DS P (a M b M A M B M ) + P (a M b P A M B M ) = P (a M b M A M B P ) + P (a M b P A M B P ) non-parameteric equality testing for the presence of sampling independence when the top part of the face is Mike and the bottom part of the face i (Mike, Paul), pertinent to inferences regarding PI P (a M b i A M B i) = [P (a M b M A M B i) + P (a M b P A M B i)] [P (a M b M A M B i) + P (a P b M A M B i)]

41 28 While there were no violations in PI and no evidence of dependencies in encoding face information at the level of the individual stimulus, it is possible that dependencies in face information exist at a different level of the composite face task. First, it is possible that perceptual dependencies exist between dimensions across all composite face stimuli rather than at the level of an individual face stimulus. These types of perceptual dependencies would be represented by violations in PS. It is also possible that dependencies could exist as interactions in the decisional criteria used to judge encoded dimensions of the composite face stimuli. These types of decisional dependencies would be represented by violations in DS. In one sense evidence of violations in PS and DS veers away from the predictions made by the holistic encoding hypothesis. This is because rather than indicating dependencies in encoding at the level of an individual composite face stimulus, violations in PS suggest dependencies in dimensions across all composite stimuli and violations in DS suggest dependencies at the level of interactions in the decisional criteria. Another perspective could interpret violations in these constructs as support for the holistic encoding hypothesis, with violations in either of these constructs indicating dependencies in representing the composite face information. However, an interpretation of violations in these constructs requires the concession that these dependencies exist at a different level than is predicted by the holistic encoding hypothesis. Inferences for PS and DS based on evidence from the marginal analyses are reported in columns labeled PS and DS in Table 2.4. This table shows there were a number of violations in PS and DS. The violations in PS are considered evidence of dependencies that exist across presentations of all the composite stimuli. The violations in DS are evidence of interactions in the decisional criteria used to judge encoded dimensions of the composite face stimuli. Overall, violations in PS and DS lend some support to the holistic encoding hypothesis. They indicate there were instances of dependent or holistic processing across dimensions of all composite face stimuli and at the level of interactions in the decisional criteria. An understanding of the way in which PS and DS are violated comes from an assessment of (a) the marginal measures of sensitivity and response bias and (b) changes in the marginal hit rates and false alarm rates. Measures of Marginal Sensitivity Measures of marginal sensitivity (d ) for the composite face stimuli are plotted for each observer in the two panels of Figure 2.5. The diagonal line in Figure 2.5a represents equality for the sensitivity measure for the top part of the composite face when the bottom part was Mike versus Paul. The points above the line indicate the ability to detect the top part of the face was higher when the bottom part of the composite face was Paul and points below the line indicate the ability to detect the top part of the face was higher when the bottom part of the face was Mike. Figure 2.5b is organized in a parallel manner. Half-filled circles and

42 Table 2.4: Experiment 1: Composite Face Identification Experiment. Summary of marginal analyses and non-parametric test of sampling independence (SI) for each observer. Evidence Inference Group Observer Age Comparison MRI d c SI PI PS DS Children Top x bottom F T F 0 T T F Bottom x top T F F 0 T T T Top x bottom T T T 0 T T T Bottom x top F T F 0 T T F Top x bottom F T F 0 T T F Bottom x top F T F 0 T T F Top x bottom F T F 0 T T F Bottom x top T F F 0 T T F Top x bottom T T T 0 T T T Bottom x top T T T 0 T T T Top x bottom T T T 0 T T T Bottom x top T T T 0 T T T Top x bottom T F T 0 T F T Bottom x top F T F 1 T T F Top x bottom T T T 0 T T T Bottom x top T T T 0 T T T Top x bottom F T T 0 T T T Bottom x top F T F 0 T T F Top x bottom T T T 0 T T T Bottom x top T T T 0 T T T Top x bottom F F F 1 T F? Bottom x top F T F 1 T T F Top x bottom T T T 0 T T T Bottom x top T T T 0 T T T Top x bottom T T T 0 T T T Bottom x top T T T 0 T T T Top x bottom T T T 0 T T T Bottom x top T T T 0 T T T Top x bottom T T T 0 T T T Bottom x top T T T 0 T T T Adults Top x bottom T T T 0 T T T Bottom x top T T T 0 T T T Top x bottom F T F 1 T T F Bottom x top F T F 0 T T F Top x bottom T T F 0 T F T Bottom x top F F T 0 T F? Top x bottom T T T 0 T T T Bottom x top T T T 0 T T T Top x bottom T T T 0 T T T Bottom x top T T T 0 T T T Top x bottom F F T 0 T F? Bottom x top T F F 0 T T T Top x bottom T T T 0 T T T Bottom x top T T T 0 T T T Top x bottom T T T 0 T T T Bottom x top T T T 0 T T T Top x bottom T T T 0 T T T Bottom x top T T T 0 T T T Top x bottom T T T 0 T T T Bottom x top T T T 0 T T T Top x bottom T T T 0 T T T Bottom x top T T T 0 T T T Note: MRI = test of marginal response invariance; d = test of marginal sensitivity; c = test of marginal response bias; T = equality holds; F = equality does not hold; The number in the SI column indicates the total number of failures of SI. 29

43 30 squares represent the data points for observers with violations in perceptual separability. In Figure 2.5a the distance of the half-filled circles and squares from the diagonal suggests theses violations in PS were driven by a greater sensitivity for detecting the top part of the composite face when the bottom part of the composite face was Paul rather than Mike. In Figure 2.5b the distance of the half-filled circle from the diagonal suggests violations in PS were driven by a greater sensitivity for detecting the bottom part of the composite face when the top part of the composite face was Paul rather than Mike. This difference in sensitivity can be analyzed to a greater degree at the level of the hit rates in Figure 2.6 and false alarm rates in Figure 2.7. An examination of these rates indicates violations of PS were primarily driven by hit rates for 3 of the 4 observers and by false alarm rates for the fourth observer. Hit rate values for two adult observers were located at a greater distance above the diagonal than other observers indicating they were more sensitive at discriminating the top or bottom of the composite faces when the other composite face was Paul rather than Mike. One child with violations in PS fell below the diagonal and below the points for other observers indicating generally lower hit rates than other observers and a greater sensitivity to correctly identify the top part of the composite face when the bottom part of the composite face was Mike versus Paul. The violations in PS for a second child appeared to be driven by higher false alarm rather than hit rates. More specifically, this child showed a greater likelihood to incorrectly respond the top of the composite face was Mike or Paul when the bottom of the composite face was Mike. In summary, the violations in perceptual separability suggest evidence of dependencies that occur across stimuli in which the ability to discriminate between the top (Figure 2.5a) and bottom (Figure 2.5b) part of the composite face is dependent on the level of the other composite part. These violations in PS are driven by differences in the hit and false alarm rates. Measures of Response Bias Measures of marginal response bias (c) for the composite face stimuli are plotted for each of the observers in the two panels of Figure 2.8. The diagonal line in Figure 2.8a represents equality for the measures of response bias for the top part of the composite face when the bottom part was Mike versus Paul. Points above the diagonal indicate a response bias that is relatively more liberal (i.e., more willing to judge the top part of the composite face as Mike) when the bottom of the composite face is Paul rather compared to Mike; points below the diagonal indicate a response bias that is relatively more conservative when the bottom of the composite face is Mike rather than Paul. The shifts in marginal response bias indicate observers were more liberal when the bottom of the composite face was Paul relative to when it was Mike, which means observers were more likely to respond the top of the composite face was Mike when the bottom of the composite was Paul rather than when it was Mike. Figure 2.8b is organized in a parallel manner. The shifts in marginal

44 31 [a] [b] Figure 2.5: Experiment 1: Points on the graph represent values of sensitivity for [a] the bottom part of the composite face at each level (Mike, Paul) collapsed across levels of the top part of the composite face [b] the bottom part of the face at each level (Mike, Paul) collapsed across levels of the top part of the composite face. Square Points: Values for children without violations (filled squares) and with violations (unfilled squares) in DS. The half-filled squares represent violations in PS with no violation in DS Circle Points: Values for adults without violations (filled circles) and with violations (unfilled circles) in DS. The half-filled circles represent violations in PS with no violation in DS.

45 32 [a] [b] Figure 2.6: Experiment 1: Points on the graph represent hit rate values for the [a] the bottom part of the composite face at each level (Mike, Paul) collapsed across levels of the top part of the composite face [b] the bottom part of the face at each level (Mike, Paul) collapsed across levels of the top part of the composite face. Square Points: Values for children without violations (filled squares) and with violations (unfilled squares) in DS. The half-filled squares represent violations in PS with no violation in DS Circle Points: Values for adults without violations (filled circles) and with violations (unfilled circles) in DS; The half-filled circles represent violations in PS with no violation in DS.

46 33 [a] [b] Figure 2.7: Experiment 1: Points on the graph represent false alarm rate values for the [a] the bottom part of the composite face at each level (Mike, Paul) collapsed across levels of the top part of the composite face [b] the bottom part of the face at each level (Mike, Paul) collapsed across levels of the top part of the composite face. Square Points: Values for children without violations (filled squares) and with violations (unfilled squares) in DS. The half-filled squares represent violations in PS with no violation in DS Circle Points: Values for adults without violations (filled circles) and with violations (unfilled circles) in DS; The half-filled circles represent violations in PS with no violation in DS.

47 34 response bias indicate observers were more liberal when the top of the composite face was Paul relative to when it was Mike, which means observers were more likely to respond the bottom of the composite face was Mike when the bottom of the composite was Paul rather than when it was Mike. Unfilled (white) circles and squares represent the data points for observers with violations in decisional separability. In Figure 2.8a the distance of the unfilled circles and squares from the diagonal suggests theses violations in DS were driven by a willingness to judge the top and bottom of the composite face as Mike when the other dimension of the composite face was Paul rather than Mike. This difference in response bias can be analyzed to a greater degree at the level of the hit rates in Figure 2.6 and false alarm rates in Figure 2.7. Observers showed a lower rate of correctly identifying a part of the composite face as Paul when it was Paul when the other other part of the composite face was Mike (i.e., a lower hit rate). Observers also showed a higher rate of incorrectly identifying a part of the composite face as Mike when it was Paul when other part of the composite face was Mike (i.e, a higher false alarm rate) Developmental Changes in Face Perception The third goal of the present study was to use GRT representations of holism to test the hypothesis that children process face information holistically and to test for evidence of qualitative and quantitative developmental changes in holistic processing across development. A dominant question in the developmental literature is whether there are changes in the ability to encode face information across the lifespan. This question is still under debate and a construct central to this debate is the construct of holism. One line of work in the developmental literature suggests children encode faces like adults as holistic, perceptual wholes at the level of the individual stimulus. It also suggests holistic encoding matures early in development and studies have reported evidence of holistic encoding in children as young as age three. Using GRT measures of dependencies, the present study tested for evidence of holistic processing in children and for evidence of qualitative and quantitative changes in encoding composite face information across the lifespan. In addition measures of sensitivity, response bias, hit rates and false alarms were also assessed for evidence of quantitative developmental changes in face perception. Qualitative Changes GRT constructs were assessed with respect to (a) evidence for holistic processing in children (b) evidence for qualitative or quantitative changes in holistic processing with development. The holistic encoding hypothesis suggests face information is encoded dependently at the level of a single face stimulus and violations in PI would be evidence of dependencies in dimensions at the level of an individual stimulus. As Table 2.4 demonstrates, equality held

48 35 [a] [b] Figure 2.8: Experiment 1: Points on the graph represent values of response bias for the [a] the bottom part of the composite face at each level (Mike, Paul) collapsed across levels of the top part of the composite face [b] the bottom part of the face at each level (Mike, Paul) collapsed across levels of the top part of the composite face. Square Points: Values for children without violations (filled squares) and with violations (unfilled squares) in DS. The half-filled squares represent violations in PS with no violation in DS Circle Points: Values for adults without violations (filled circles) and with violations (unfilled circles) in DS; The half-filled circles represent violations in PS with no violation in DS.

49 36 in all conditions for observers. Both children and adults showed no violations in perceptual independence. This is evidence that children encode face information independently like adults at the level of an individual composite face stimulus. It is also evidence against the holistic encoding hypothesis, which suggests children and adults encode face information holistically at the level of an individual stimulus. In addition to the tests of perceptual independence the data were evaluated for evidence of developmental differences in violations of PS and DS. As Table 2.4 indicates, there were instances in which equality held and instances of violations in PS and DS for children and adults. Figure 2.9 plots the sum of the number of violations of PS and DS by age. A difference in the number of violations in PS relative to the number of violations in DS could indicate a possible qualitative change in holistic processing with age. Evidence of an increase or decrease in the number of violations in PS or DS with age could reflect a possible quantitative change in holistic processing with age. The purpose of assessing the number of violations in DS and PS by age is to provide a general overview of the type and number of violations by age. This is a rough observational assessment that was not subject to statistical testing. There were no robust age-related differences evident in the plot of number of violations in PS or DS for the top part of the composite face across dimensions of the bottom (T x b). There were also no robust age-related differences in the plot of number of violations in PS for bottom part of the composite face across dimensions of the top (B x t). There did appear to be an age-related difference in the number of violations in DS for the bottom part of the composite face across dimensions of the top (B x t). Critically, children under the age 12 had a greater number of violations in DS than older children and adults. If this is a true reflection of an age-related difference, it would suggest judgements of the bottom part of the composite face are more consistently affected by the level of the top part of the face for children under the age 12 compared to older children or adults. Quantitative Changes Up until this point, the evidence generally suggests that children encode composite face information in a qualitatively similar manner as adults. First, the assessment of the GRT constructs showed violations in PS and DS with no violations in PI. Contrary to the holistic encoding hypothesis, this suggests both children and adults encoded the dimensions of the composite face information independently at the level of an individual composite face stimulus. Second, adults and children both showed violations in PS and DS, which provides evidence of dependencies in dimensions across stimuli and at the level of interactions in the judgments of the stimuli. While these dependencies do not occur at the specific level predicted by the holistic encoding hypothesis, it provides some evidence that dependencies in encoding occur across composite face stimuli and at the level of response criteria in the composite face task.

50 Figure 2.9: Experiment 1: Total number of violations of PS and DS by age. 37

51 38 In addition to reporting evidence of qualitative changes in face perception, a large number of studies in the developmental face literature have reported evidence of age-related quantitative changes in face perception. For example, Flin (1985) and Itier and Taylor (2004) reported age-related incremental improvements in sensitivity on two inversion tasks suggesting that there quantitative rather than qualitative improvements in face perception with development. The present study used linear regression analyses to assess whether there was evidence of quantitative developmental changes in face perception for measures of sensitivity (d ), response bias(c), hit rate rates and false alarm rates. Figures are plots of the regression lines for each of these measures and Table 2.5 presents the results of the regression analyses. Linear regression analyses revealed significant age-related increases in sensitivity (d values) across the entire sample of children and adults (solid line) and separately for children ages 6-15 (dotted line). These analyses also revealed a significant age-related decrease in false alarm rate (see Figure 2.12), whereas age-related changes in hit rate only showed a single instance of approaching significance (see Figure 2.11). This suggests that the age-related increases in sensitivity were primarily driven by a significant decrease in false alarm rates rather than an increase in the hit rates. Regression analyses were also performed to assess age-related changes in response criteria. While linear regression analyses revealed no significant changes in response criteria with age (see Figure 2.13), quadratric regression analyses were also performed and were significant (see Figure 2.14). The results of the quadratic regression analyses indicate a shift from judgments on the composite task that were relatively unbiased to judgments that became more conservative peaking at points in adolescence between the ages of 10 and 15.

52 39 [a] [b] Figure 2.10: Experiment 1: Measures of marginal sensitivity by age for (a) T x b: a change in the top part of the composite face across levels of the bottom (b) B x t: a change in the bottom part of the composite face across levels of the top. The solid line is the regression line for all observers. The dotted line is the regression line for children (ages 6-15) only. Results of the linear regression analyses are reported in row 1 of Table 2.5.

53 40 [a] [b] Figure 2.11: Experiment 1: Hit rate by age for (a) T x b: a change in the top part of the composite face across levels of the bottom (b) B x t: a change in the bottom part of the composite face across levels of the top. The solid line is the regression line for all observers. The dotted line is the regression line for children (ages 6-15) only. Results of the linear regression analyses are reported in row 4 of Table 2.5.

54 41 [a] [b] Figure 2.12: Experiment 1: False alarm rate by age for (a) T x b: a change in the top part of the composite face across levels of the bottom (b) B x t: a change in the bottom part of the composite face across levels of the top. The solid line is the regression line for all observers. The dotted line is the regression line for children (ages 6-15) only. Results of the linear regression analyses are reported in row 5 of Table 2.5.

55 42 [a] [b] Figure 2.13: Experiment 1: Measures of marginal response bias by age for (a) T x b: a change in the top part of the composite face across levels of the bottom (b) B x t: a change in the bottom part of the composite face across levels of the top.the solid line is the regression line for all observers. The dotted line is the regression line for children (ages 6-15) only. Results of the linear regression analyses are reported in row 2 of Table 2.5.

56 43 [a] [b] Figure 2.14: Experiment 1: Measures of marginal response bias for (a) T x b: a change in the top part of the composite face across levels of the bottom (b) B x t: a change in the bottom part of the composite face across levels of the top. The solid line is the regression line for all observers. The dotted line is the regression line for children (ages 6-15) only. Results of the quadratic regression analyses are reported in row 3 of Table 2.5.

57 44 Table 2.5: Experiment 1: Regression results and equations for sensitivity (d ), response bias (c), hit rates and false alarm rates. Measure Level Line Type Group Significance Regression Equation Sensitivity (d ) Linear Regression T x b Solid Line All Observers R 2 =.29, F (1, 24) = 9.92, p =.004 y = 0.04x T x b Dotted Line Children (ages 6-15) R 2 =.34, F (1, 13) = 12.60, p =.002 y =.07x +.90 B x t Solid Line All Observers R 2 =.34, F (1, 24) = 12.60, p =.00 y =.04x B x t Dotted Line Children (ages 6-15) R 2 =.46, F (1, 13) = 10.96, p =.01 y =.10x +.47 Response Bias (c) Linear Regression T x b Solid Line All Observers R 2 =.01, F (1, 24) =.21, p =.65 y =.00x +.08 T x b Dotted Line Children (ages 6-15) R 2 =.11, F (1, 13) = 1.57, p =.23 y =.02x.06 B x t Solid Line All Observers R 2 =.11, F (1, 24) = 2.84, p =.10 y =.01x.03 B x t Dotted Line Children (ages 6-15) R 2 =.01, F (1, 13) = 0.19, p =.67 y =.01x +.01 Response Bias (c) Quadratic Regression T x b Solid Line All Observers R 2 =.09, F (1, 23) = 2.36, p =.14 y = 0.01x x 1.25 T x b Dotted Line Children (ages 6-15) R 2 =.24, F (1, 12) = 4.43, p =.06 y = 0.01x x 1.08 B x t Solid Line All Observers R 2 =.00, F (1, 24) =.25, p =.62 y = 0.00x x.19 B x t Dotted Line Children (ages 6-15) R 2 =.43, F (1, 13) = 9.19, p =.01 y = 0.01x x 1.25 Hit Rates Linear Regression T x b Solid Line All Observers R 2 =.12, F (1, 24) = 3.33, p =.08 y =.01x +.76 T x b Dotted Line Children (ages 6-15) R 2 =.00, F (1, 13) = 0.04, p =.84 y =.00x +.79 B x t Solid Line All Observers R 2 =.02, F (1, 24) = 0.45, p =.51 y =.00x +.78 B x t Dotted Line Children (ages 6-15) R 2 =.12, F (1, 13) = 1.70, p =.22 y =.01x +.70 False Alarm Rates Linear Regression T x b Solid Line All Observers R 2 =.15, F (1, 24) = 4.30, p =.05 y =.00x +.16 T x b Dotted Line Children (ages 6-15) R 2 =.35, F (1, 13) = 7.11, p =.02 y =.01x +.23 B x t Solid Line All Observers R 2 =.45, F (1, 24) = 19.48, p =.00 y =.01x +.22 B x t Dotted Line Children (ages 6-15) R 2 =.44, F (1, 13) = 10.20, p =.00 y =.02x +.32

58 45 Chapter 3 Experiment Purpose The first purpose of the second experiment wass to test a major assumption underlying the dual-mode hypothesis. This assumption proposes that children and adults encode featural and configural information independently in upright and inverted faces. The second goal is to assess measures provided by general recognition theory and measures of sensitivity (d ), response bias (c), hit rates and false alarm rates for evidence of qualitative and quantitative developmental changes in the representation of face information. 3.2 Methods Participants Eleven adults and 18 children participated in this experiment. Six adults and nine children were female and five adults and eight children were male. The adult participant group was comprised of Penn State undergraduate students and individuals ages recruited from local internet and bulletin board advertisements. Children ages 5-17 were also recruited via local internet and bulletin board advertisements. All participants had normal to correctedto-normal vision and unencumbered use of both hands. All participants were right-handed except for two participants except for one adult and one child. None of the participants were diagnosed with a language, hearing, visual, neurological, developmental or psychiatric disorder. Participants were paid $8 per hour for their participation. Children were also given the opportunity to select a small gift from a prize box Materials The two photographs used to construct stimuli for the composite face experiment (experiment 1) were used to construct the stimuli for experiment 2. These photographs were of two Caucasian males enrolled in the Psychology Program at the Pennsylvania State University. There were four categories of stimuli were created from each source image. An example of each of the types of stimuli is presented in Figure 3.1. The first type of stimulus

59 46 was an unaltered image of the model presented in grayscale. The second type of stimulus image was created to represent a change in featural information only. These images had enlarged lips. The third type of stimulus image created to represent a change in configural information only. The eyes were crossed resulting in a change to the internal geometry of the face. The fourth type of stimulus was created to represent a change in both configural and featural information. These images had crossed eyes with enlarged lips. Models wore a surgical cap and scrubs in order to hide their hair and clothing. Images of their faces were presented inside an oval surrounded by a 50% gray background (RGB value 149). This was to replicate other researchers that present face stimuli in this manner in order to eliminate cues derived from the shape of the head or chin. Images were sized at 4.76 cm (v) 2.59 cm (h). When viewed at a fixed distance of 76 cm, the images subtended 3.58 (vertically) and 1.95 (horizontally). Figure 3.1: Experiment 2: Types of Stimulus Displays

60 3.2.3 Design and Procedure 47 The experiment was conducted as a (Orientation: Upright, Inverted) 2 (Configural Change: Present, Absent) 2 (Featural Change: Present, Absent) factorial design. Participants completed a single session of this experiment. A schematic representation of the factorial is presented in Figure 3.2 in the context of GRT predictions for the present inversion experiment. Each condition was presented with equal frequency. Adult participants began each session with five minutes of dark adaptation. The door to the testing room was kept partially open during testing sessions with children so they could be monitored during the task. Although children were not adapted to the dark by conventional standards (i.e. in a dark room with the door closed), the door was closed 3/4 of the way, the lights were turned off in the testing room and the laboratory during sessions. Participants were seated at a viewing distance of approximately 76 cm from the computer monitor. Adults used a chin rest to maintain head position; children were not required to use a chin rest. Children were also provided with an opportunity to pick out a sticker as a reward for completing each section of the experiment. Participants completed as many trials as possible in a single 90 minute session and had an unlimited amount of time to make each of two responses on each trial. They were told they could take a break from the experiment at any point in time. The number of trials participants were able to complete for Experiment 2 had a wide range between 282 trials to 2037 trials. Adults completed more trials in a single session than children. This is primarily because children took longer to respond on each trial and took more breaks than adults from the experiment during the 90 minute testing session. Table 4.1 provides information about the specific number of trials each observer was able to complete for Experiment 2. Blocks of trials with faces in the upright and inverted orientation were presented separately. The type of block presented first was counterbalanced within age group (children versus adults). Half of the participants in the each group completed the task with faces in the upright orientation. Each block contained approximately 226 trials. The orientation of the face stimuli was switched halfway through the testing session. Participants completed a block of 12 practice trials in the given orientation and were allowed to begin the test trial when they reached a level of at least 70% accuracy on the practice trials in a given orientation Figure 3.3 shows an example of a single test trial participants completed during the task practice and the test portion of the session. Each trial was self-initiated and began with a small black dot on the screen. When the participant was ready to begin a trial, they pressed a button on the keyboard. A fixation cross was presented with a random fore-period and a uniform distribution ranging from 300 to 700 ms. The offset of the fixation cross was followed by a 100 ms presentation of a blank screen and then the presentation of the first face stimulus (referred to as the study face).

61 Figure 3.2: Experiment 2: Schematic representation of GRT predictions for the configuralfeatural inversion experiment: [a] no violations [b] violation of PS [c] violation of PI [d] violation of DS. 48

62 49 Figure 3.3: Experiment 2: Events on Each Experimental Trial The study face appeared on the screen for the 1000 ms followed by a test face. The test face remained on the screen and the participant was asked to make two sequential responses. First, the participant was cued by an asterisk above the top or below the bottom part of the face. The participant was instructed to press the [ z ] button if the cued part of the face was different from the study face and the [ / ] button if they thought the cued part was the same as the study face. After the first response, the test stimulus remained on the computer screen and the asterisk moved above or below the previously uncued part of the face. The participant was asked to make a second response indicating whether they thought this part of the face was the same or different from the first part of the study face. The stimulus image was followed by a blank mid-gray screen for ms. In order to make the experimental task more engaging for the children, the experiment was presented in the context of a board game. Children were also provided with the option of picking out a sticker as a reward for completing a block of the experiment. 3.3 Results and Discussion Data from the inversion task experiment was evaluated in reference to three questions: (a) Did the stimuli used in the present study replicate the inversion effect reported in previous studies of the inversion effect? (b) Were there violations in PI, PS and/or DS and did these violations change with age? (c) Was there evidence of developmental changes in the ability

63 to encode face information? A criterion(α) of 0.05 was used to infer statistical reliability in all cases Inversion Effect The first goal of the present study was to analyze the data for evidence of the inversion effect in order to replicate previous studies using this experimental task. Several previous studies have reported greater accuracy, sensitivity (d ) and a significantly shorter response times when face stimuli are presented in an upright versus an inverted orientation. Researchers have interpreted these findings with respect to operational definitions for two types of face information: featural face information and configural face information. Featural information is often defined in the literature as information about the characteristics of facial features such as the color of the eyes or shape of the nose. Configural information is often described as the spatial relationship between the features such as the relative distance between the nose to the eyes. Researchers suggest that individuals encode both types of face information when a face is held in an upright orientation. In addition, they suggest that when a face is inverted the ability to encode the configural information of a face is disrupted resulting in poorer performance in this condition on face perception tasks. Mean values for measures of sensitivity (d ) and the 95% confidence intervals for these measures were calculated for all observers in the upright and inverted conditions and are presented in Figures and Tables Confidence intervals for measures of marginal sensitivity were calculated according to Gourevitch and Galanter (1967). The diagonal line in Figures represents equality for values of sensitivity in the upright and inverted conditions; points above the line represent mean measures of sensitivity that were higher in the inverted versus the upright condition, whereas points below the line represent mean measures of sensitivity that were higher in the upright versus inverted condition. Figures generally fell below the diagonal line suggesting a trend for greater sensitivity in the upright condition.the columns labeled CI Status in Tables lists the status of the confidence intervals for the upright and inverted conditions indicating if they did or did not overlap. Confidence intervals did not overlap for 3 of the 14 children and 4 of the 11 adult observers in the condition where values for the featural condition were collapsed across levels of the configural condition (C x f). Confidence intervals did not overlap for 5 of the 14 children and 0 of the 11 adult observers in the condition where values for the configural condition were collapsed across levels of the featural condition (F x c). Differences in the upright and inverted conditions were also tested across participants at the level of the group mean. These results are reported in Table 3.3. At the level of the group mean, only children showed significantly higher sensitivity in the upright versus inverted conditions.

64 Figure 3.4: Experiment 2: The inversion effect (C x f) for: (a) Children ages 6-17 (b) Adults ages Values to below the diagonal indicate greater sensitivity for upright compared to inverted conditions. This ordering would be consistent with the inversion effect frequently reported in previous inversion experiments. 51

65 Figure 3.5: Experiment 2: The inversion effect (F x c) for: (a) Children ages 6-17 (b) Adults ages Values to below the diagonal indicate greater sensitivity for upright compared to inverted conditions. This ordering would be consistent with the inversion effect frequently reported in previous inversion experiments. 52

66 Table 3.1: Experiment 2: Measures of marginal sensitivity (d ) for upright and inverted conditions for levels of the featural condition collapsed across levels of the configural condition (C x f). The 95% confidence intervals calculated using Gourevitch and Galanter (1967) estimators. Note: CI Status indicates whether the 95% confidence intervals for measures of sensitivity overlap (YES) or do not overlap (NO). A reliable difference in marginal sensitivity (*) for the upright and inverted conditions is noted for confidence intervals that do not overlap. Upright(95% CI) Inverted (95% CI) Group Observer Age Upright (d ) Inverted (d ) Lower Bound Upper Bound Lower Bound Upper Bound CI Status Children YES YES YES YES YES YES *NO YES *NO YES YES YES *NO YES Adults *NO *NO YES *NO YES *NO YES YES YES YES YES 53

67 Table 3.2: Experiment 2: Measures of marginal sensitivity (d ) for upright and inverted conditions for levels of the configural condition collapsed across levels of the featural condition (F x c). The 95% confidence intervals calculated using Gourevitch and Galanter (1967) estimators. Note: CI Status indicates whether the 95% confidence intervals for measures of sensitivity overlap (YES) or do not overlap (NO). A reliable difference in marginal sensitivity (*) for the upright and inverted conditions is noted for confidence intervals that do not overlap. Upright(95% CI) Inverted (95% CI) Group Observer Age Upright (d ) Inverted (d ) Lower Bound Upper Bound Lower Bound Upper Bound CI Status Children YES *NO YES YES YES YES *NO *NO *NO YES *NO YES YES YES Adults YES YES YES YES YES YES YES YES YES YES YES 54

68 Table 3.3: Experiment 2: One-way ANOVA tests of the inversion effect at the level of group means Upright Inverted Group Level Mean SD Mean SD F Value Significance All Participants C x f F (1, 48) = 1.66 p =.20 Adults C x f F (1, 20) = 0.89 p =.36 Children C x f F (1, 26) = 3.61 p =.07 All Participants F x c F (1, 48) = 1.66 p =.20 Adults F x c F (1, 20) = 0.04 p =.84 Children F x c F (1, 26) = 5.41 p = Multidimensional Signal Detection Analyses The second goal of this experiment was to test the assumption that children and adults process featural and configural information independently in upright and inverted faces using the statistical measures and logical inferences provided by general recognition theory. Statistical evidence was analyzed and inferences with respect to possible violations of PI, PS, and DS. A schematic representation of the four GRT models used to demonstrate predictions for the inversion face task are presented in Figure 3.2. In order to draw inferences about violations in PI, PS, and DS each observer s performance was first summarized in a 4 (each stimulus state) row 4 (each possible response) column matrix. The distribution of response frequencies in each observer s matrix were tested using a set of equalities that were first developed by Ashby and Townsend (1986) and have been shown to hold under the assumptions of PI, PS, and DS (Ashby & Townsend, 1986; Kadlec, 1999, 1992; Kadlec & Townsend, 1992). Table 2.2 provides a summary of the estimates and equalities as they relate to the inferential logic initially developed by (Ashby & Townsend, 1986; Kadlec, 1992). The question marks noted in Table 2.2 represent instances in which the evidence from marginal measures suggesting DS holds is uncertain subsequently making any inferences predicated on DS holding uncertain as well. As noted in experiment 1 of the present study, one approach for resolving these uncertainties is to fit fully-specified multivariate gaussian models to the identification-confusion matrices using an approach outlined by Thomas (2001). While these models have not yet been fit to the identification confusion matrices for observers in experiment 2, they will be in the future in order to resolve these uncertainties in the data. Table 3.4 provides a specific list of the marginal measures of performance used to make inferences about the status of PI, PS and DS (i.e., whether equality holds or the construct is violated) for the present experiment. As noted for experiment 1, non-parametric tests of sampling independence were also used in order to further clarify inferences regarding violations in PI. The results from the comparisons of the marginal measures and inferences based on evidence from these measures regarding each of the GRT constructs (i.e., PI, PS,

69 DS) are summarized in Tables Table 3.4: Experiment 2: Marginal measures of performance used to guide inferences regarding PI, PS, and DS, considering the relationship between the status (different and same) of two internal elements of the test stimuli. Quantity P (a Db i A DB i) P (a Db i A SB i) d (A, B i) c(a, B i) MRI SI Definition and description marginal probability of correctly identifying the configuration as being Different ( hit ) when the state of the lips is i (Different, Same) marginal probability of incorrectly identifying the configuration as being Different ( false alarm ) when the state of the lips is i(different, Same) marginal sensitivity to the correct state of the configuration when the featural element is in state i (Different, Same) = 1 2 {z[p (a Db i A DB i)] z[p (a Db i A SB i)]} marginal criterion for reporting the configuration as Different when the state of the lips is i (Different, Same) = 1 2 {z[p (adbi ADBi)] + z[p (adbi ASBi)]} 2 non-parametric equality testing for the presence of marginal response invariance, pertinent to inferences regarding PS and DS P (a Db D A DB D) + P (a Db S A DB D) = P (a Db D A DB S) + P (a Db S A DB S) non-parameteric equality testing for the presence of sampling independence when the configuration of the eyes is Different and the state of the lips is i (Same, Different), pertinent to inferences regarding PI P (a Db i A DB i) = [P (a Db D A DB i) + P (a Db S A DB i)] [P (a Db D A DB i) + P (a Sb D A DB i)] Inferences Regarding PI, PS, and DS One assumption of the dual-mode hypothesis is that information about facial features is encoded independently from information about the spatial configuration at the level of an individual face stimulus. Further, inverting a face stimulus is assumed to preferentially disrupt the encoding of the spatial relationships between features while the ability to encode information about the features remains intact. Evidence that changes in configural and featural face information are encoded independently at the level of the representation of the individual face would be instances in which perceptual independence holds. As Tables document, there were no violations of PI suggested for any of the observers in any of the conditions. This evidence in favor of the assumption that configural and featural face information are represented in an independent manner. While there was no evidence of dependencies in encoding face information at the level of the individual stimulus, it is possible that dependencies in face information exist at a different level of the inversion face task. First, it is possible that perceptual dependencies exist between dimensions across all face stimuli rather than at the level of an individual

70 57 face stimulus. These types of perceptual dependencies would be represented by violations in PS. It is also possible that dependencies could exist as interactions in the decisional criteria used to judge encoded dimensions of the face stimuli. These types of decisional dependencies would be represented by violations in DS. Evidence of violations in these constructs could be interpreted as evidence against the assumption that configural and featural face information are represented independently. Violations in PS would suggest dependencies in dimensions across all face stimuli and violations in DS would suggest dependencies at the level of interactions in the decisional criteria. An interpretation of violations in these constructs requires the concession that these dependencies do not exist at the level of the individual stimulus as is assumed by the dual mode hypothesis. Inferences for PS and DS based on evidence from the marginal analyses are reported in columns labeled PS and DS in Tables These table demonstrate that there were a number of violations in PS and DS in both the upright and inverted conditions. The violations in PS are considered evidence of dependencies that exist across presentations of all the upright and inverted face stimuli. The violations in DS are evidence of interactions in the decisional criteria used to judge encoded dimensions of the upright and inverted face stimuli. Overall, violations in PS and DS provide some evidence against the assumption that featural and configural face information are represented independently. They suggest there were instances of the dependent representation of configural and featural information across dimensions of all upright and inverted face stimuli and at the level of interactions in the decisional criteria. An understanding of the way in which PS and DS are violated comes from an assessment of (a) the marginal measures of sensitivity and response bias and (b) changes in the marginal hit rates and false alarm rates. Measures of Marginal Sensitivity Measures of marginal sensitivity (d ) for face stimuli in upright and inverted conditions are plotted for each observer in Figures The diagonal line in Figure 3.6a and 3.7a represents equality for the sensitivity measure across the levels of the configural condition when featural information remained the same (i.e., the size lips was identical in the study and the test face) or was different (i.e., the lips were bigger in the test face). The points above the line indicate sensitivity in the configural condition was higher when the featural information in the study and test faces was the same rather than different. Points below the line indicate the ability to detect the top part of the face was higher when the featural information was different in the study and the test faces. Figures 3.6b and 3.7b represent equality for the sensitivity measure across the levels of the featural condition when featural information remained the same (i.e., the configuration of the eyes was identical in the study and the test face) or was different (i.e., the eyes were normal in the study face and crossed in the test face).

71 58 Half-filled circles and squares represent the data points for observers with violations in perceptual separability. In Figures 3.6a and 3.7a the distance of the half-filled circles and squares from the diagonal suggests theses violations in PS were driven by a greater sensitivity for detecting whether the configuration was the same or different in the study and test faces when the feature was the same rather than when it was different. In Figures 3.6b and 3.7b the distance of the half-filled circles and squares from the diagonal suggests violations in PS for children were driven by a greater sensitivity for detecting whether the facial features were the same or different in the study and test faces when the configuration of the face was the same rather than different. One adult observer represented by the half-filled circle in Figure 3.7b showed a contrasting pattern with a greater sensitivity for detecting whether the facial features were the same or different in the study and test faces when the configuration of the face was the different rather than the same. Differences in sensitivity can be analyzed to a greater degree at the level of the hit rates in Figures and false alarm rates in Figures An examination of these rates suggests violations in PS for the upright and inverted conditions were primarily driven by a higher hit rate or a greater ability of observers to correctly identify a difference in configural or featural information when the status of the other type of face information was different rather than the same. This finding is coupled with a much higher false alarm rate indicating that observers were more likely to incorrectly report there was a difference in configural or featural face information when there was difference in the other other dimension. In summary, the violations in perceptual separability suggest evidence of dependencies that occur across stimuli in both the upright and inverted conditions; the ability to discriminate changes in configural face information is dependent on changes in featural information and vice versa. Violations in PS appear to be driven by differences in both the hit and false alarm rates in both the upright and inverted conditions. Measures of Response Bias Measures of marginal response bias (c) for the upright and inverted fade stimuli are plotted for each of the observers in the Figures The diagonal line in Figures 3.12a and 3.13a represents equality equality for the measures of response bias across the levels of the configural condition when featural information remained the same (i.e., the size lips was identical in the study and the test face) or was different (i.e., the size of the lips changed between the study and the test face). Points above the diagonal indicate a response bias that is relatively more liberal (i.e., more willing to respond there is a difference in configuration) when the featural dimension is the same rather then different; points below the diagonal indicate a response bias that is relatively more conservative when the featural dimension is different compared to when it is the same. The shifts in marginal response bias indicate observers were liberal and more willing to judge the configuration as different when the

72 59 [a] [b] Figure 3.6: Experiment 2: Points on the graph represent values of sensitivity in the upright condition for [a] the featural condition at each level (Different, Same) collapsed across levels of the configural change [b] the configural condition at each level (Different, Same) collapsed across levels of the featural change. Square Points: Values for children without violations (filled squares) and with violations (unfilled squares) in DS. The half-filled squares represent violations in PS with no violation in DS Circle Points: Values for adults without violations (filled circles) and with violations (unfilled circles) in DS. The half-filled circles represent violations in PS with no violation in DS.

73 60 [a] [b] Figure 3.7: Experiment 2: Points on the graph represent values of sensitivity in the inverted condition for [a] the featural condition at each level (Different, Same) collapsed across levels of the configural condition [b] the configural conditionat each level (Different, Same) collapsed across levels of the featural condition. Square Points: Values for children without violations (filled squares) and with violations (unfilled squares) in DS. The half-filled squares represent violations in PS with no violation in DS Circle Points: Values for adults without violations (filled circles) and with violations (unfilled circles) in DS. The half-filled circles represent violations in PS with no violation in DS.

74 61 [a] [b] Figure 3.8: Experiment 2: Points on the graph represent hit rates in the upright condition for [a] the featural condition at each level (Different, Same) collapsed across levels of the configural condition [b] the configural condition at each level (Different, Same) collapsed across levels of the featural condition. Square Points: Values for children without violations (filled squares) and with violations (unfilled squares) in DS. The half-filled squares represent violations in PS with no violation in DS Circle Points: Values for adults without violations (filled circles) and with violations (unfilled circles) in DS. The half-filled circles represent violations in PS with no violation in DS.

75 62 [a] [b] Figure 3.9: Experiment 2: Points on the graph represent the hit rates in the inverted condition for [a] the featural condition at each level (Different, Same) collapsed across levels of the configural condition [b] the configural conditionat each level (Different, Same) collapsed across levels of the featural condition. Square Points: Values for children without violations (filled squares) and with violations (unfilled squares) in DS. The half-filled squares represent violations in PS with no violation in DS Circle Points: Values for adults without violations (filled circles) and with violations (unfilled circles) in DS. The half-filled circles represent violations in PS with no violation in DS.

76 63 [a] [b] Figure 3.10: Experiment 2: Points on the graph represent false alarm rates in the upright condition for [a] the featural condition at each level (Different, Same) collapsed across levels of the configural condition [b] the configural condition at each level (Different, Same) collapsed across levels of the featural condition. Square Points: Values for children without violations (filled squares) and with violations (unfilled squares) in DS. The half-filled squares represent violations in PS with no violation in DS Circle Points: Values for adults without violations (filled circles) and with violations (unfilled circles) in DS. The half-filled circles represent violations in PS with no violation in DS.

77 64 [a] [b] Figure 3.11: Experiment 2: Points on the graph represent false alarm rates in the inverted condition for [a] the featural condition at each level (Different, Same) collapsed across levels of the configural condition [b] the configural condition at each level (Different, Same) collapsed across levels of the featural condition. Square Points: Values for children without violations (filled squares) and with violations (unfilled squares) in DS. The half-filled squares represent violations in PS with no violation in DS Circle Points: Values for adults without violations (filled circles) and with violations (unfilled circles) in DS. The half-filled circles represent violations in PS with no violation in DS.

78 65 featural dimension is the same rather than different. Unfilled (white) circles and squares represent the data points for observers with violations in decisional separability. In Figures 3.12a a the distance of the unfilled circles and squares from the diagonal suggests theses violations in DS were driven by a willingness to judge the configuration of upright and inverted faces as different when the featural dimension was the same rather than different. This difference in response bias can be analyzed to a greater degree at the level of the hit rates in Figures 3.8a - 3.9a and false alarm rates in Figures 3.10a a. Observers showed a higher rate of correctly identifying a difference in the configuration when the featural dimension was different compared to when it was the same. Observers also showed a higher false alarm rate indicating that they had a greater rate of incorrectly identifying the configuration was different when the featural dimension was different compared to when the featural dimension was the same. In summary, the violations in DS suggest evidence of dependencies that occur for upright and inverted faces at the level of interactions in judgments of the stimuli; judgments of the same-different status of the configural face information are dependent on judgments about the featural information. Violations in DS appear to be driven by differences in both the hit and false alarm rates in both the upright and inverted conditions Developmental Changes in Face Perception The third goal of the present experiment was to use GRT representations of holism to test a major assumption of the dual-mode hypothesis. This assumption suggests children and adults process information about the physical aspects of facial features (e.g., shape, size) independently from information about the spatial configurations of the facial features at the level of an individual face stimulus. Further, inverting a face stimulus is assumed to preferentially disrupt the encoding of the spatial relationships between features while the ability to encode information about the features remains intact. The assumption that there are two independent types of face information plays a significant role in the developmental face perception literature. Many studies have reported differences in experimental data for manipulations that are based on modal definitions for configural and featural information and the assumption that these two types of information are processed independently. Results from these experiments have resulted in several hypotheses that use these modal definitions as a basis for making predictions about developmental changes in face perception. One drawback of this approach is that the use of these operational definitions often leads to circular reasoning. It has also led to inconsistent inferences about whether developmental changes in face perception occur and a continued debate over whether these changes are qualitative or quantitative. Using GRT measures of dependencies, the present study tested for evidence that configural and featural face information is encoded independently and for evidence of qualitative and quantitative changes in encoding this information across

79 66 [a] [b] Figure 3.12: Experiment 2: Points on the graph represent measures of response bias in the upright condition for [a] the featural condition at each level (Different, Same) collapsed across levels of the configural condition [b] the configural condition at each level (Different, Same) collapsed across levels of the featural condition. Square Points: Values for children without violations (filled squares) and with violations (unfilled squares) in DS. The half-filled squares represent violations in PS with no violation in DS Circle Points: Values for adults without violations (filled circles) and with violations (unfilled circles) in DS. The half-filled circles represent violations in PS with no violation in DS.

80 67 [a] [b] Figure 3.13: Experiment 2: Points on the graph represent measures of response bias in the inverted condition for [a] the featural condition at each level (Different, Same) collapsed across levels of the configural condition [b] the configural condition at each level (Different, Same) collapsed across levels of the featural condition. Square Points: Values for children without violations (filled squares) and with violations (unfilled squares) in DS. The half-filled squares represent violations in PS with no violation in DS Circle Points: Values for adults without violations (filled circles) and with violations (unfilled circles) in DS. The half-filled circles represent violations in PS with no violation in DS.

81 68 the lifespan. In addition to an evaluation of results from the GRT measures, measures of sensitivity, response bias, hit rates and false alarms were also assessed for evidence of quantitative developmental changes in face perception. Qualitative Changes GRT constructs were assessed with respect to (a) evidence that information about changes in the physical characteristic of a facial feature (i.e., the size of the lips) is encoded independently from information about changes in the configuration of the features (i.e., crossed eyes) (b) evidence for qualitative or quantitative changes in encoding across development. The dual-mode hypothesis suggests information about the configuration of the facial features is encoded independently from information about changes in the physical characteristics of these features. Instances in which PI holds would be evidence of the independent representation of changes in featural and configural information at the level of an individual stimulus. As Tables demonstrate, equality held in all conditions for observers. Both children and adults showed no violations in perceptual independence. This is evidence that children and adults encoded changes in facial features and changes in the configuration of the facial features independently in upright and inverted conditions. It is also evidence supporting the assumption of the dual-mode hypothesis, which predicts information about facial features and their configuration are encoded as independent sources of information. In addition to the tests of perceptual independence the data were evaluated for evidence of developmental differences in violations of PS and DS. As Tables indicate, there were instances in which equality held and instances of violations in PS and DS for children and adults in upright and inverted conditions. Figures plot the sum of the number of violations of PS and DS by age in the upright and inverted conditions. A difference in the number of violations in PS relative to the number of violations in DS could indicate a possible qualitative change in dependencies in encoding with age. Evidence of an increase or decrease in the number of violations in PS or DS with age could reflect a possible quantitative change in dependencies in encoding with age. The purpose of assessing the number of violations in DS and PS by age is to provide a general overview of the type and number of violations by age. This is a rough observational assessment that was not subjected to statistical testing. Both children and adults showed a greater number of violations in PS than DS in both the upright and inverted conditions. There only appeared to be an age-related difference in the number of violations in PS in one condition. Children under the age of 12 showed a greater overall number of violations in PS than older adults and children in the upright condition when levels of the configuration of the face were collapsed across the featural dimension (Upright, F x c). If this reflects a true difference, it suggests the ability of children under the age of 12 to discriminate changes in the features (i.e., the size of the lips) in upright faces was more consistently affected by the status of the configuration

82 (i.e., same, different) than it was for older children and adults. 69 Quantitative Changes Up until this point, the evidence generally suggests that children encode upright and inverted face information in a qualitatively similar manner as adults. First, the assessment of the GRT constructs showed violations in PS and DS with no violations in PI. In accordance with one underlying assumption of the dual-mode hypothesis, this suggests adults and children encoded changes in the configuration of facial features and information about changes in a physical characteristic of the facial features independently. This was true for faces presented in both upright and inverted orientations. Second, adults and children both showed violations in PS and DS in the upright and inverted orientations. This is evidence of dependencies in dimensions across stimuli and at the level of interactions in the judgments of the stimuli. This could be interpreted as evidence against the assumption of the dual-mode hypothesis that configural and featural face information is encoded independently. Linear regression analyses were performed to assess whether there was evidence of quantitative developmental changes in face perception for measures of sensitivity (d ), response bias (c), hit rate rates and false alarm rates. Figures are plots of the regression lines for each of these measures and Table 3.7 presents the results of the regression analyses. Linear regression analyses revealed significant age-related increases in sensitivity (d values) across the entire sample of children and adults (solid line) for faces in both the upright and inverted conditions (see Figures ).These analyses also revealed evidence of a significant age-related decrease in false alarm rate (see Figures ) and evidence of an age-related increase in hit rates (see Figures ) in upright and inverted conditions across all observers. There was also one instance in whereas age-related changes in hit rate only showed a single instance of approaching significance(see Figure 2.11). This suggests that the age-related increases in sensitivity were driven by a significant decrease in false alarm rates and a significant increase in hit rates. Regression analyses were also performed to assess age-related changes in response criteria. There was no significant evidence of agerelated changes changes in response criteria in linear (see Figures ) or quadratic regression analyses (see Figures ).

83 Figure 3.14: Experiment 2: Upright Trials: Total number of violations of PS and DS by age. 70

84 Figure 3.15: Experiment 2: Inverted Trials: Total number of violations of PS and DS by age. 71

85 72 [a] [b] Figure 3.16: Experiment 2: Upright Trials: Measures of sensitivity by age for: (a) C x f: a change in configuration across levels of the featural change (b) F x c: a change in facial feature across levels of the configuration.

86 73 [a] [b] Figure 3.17: Experiment 2: Inverted Trials: Measures of sensitivity by age for: (a) Cxf: a change in configuration across levels of the featural change (b) Fxc: a featural change across levels of a change in configuration.

87 74 [a] [b] Figure 3.18: Experiment 2: Upright Trials: False alarm rate by age for: (a) Cxf: a change in configuration across levels of the featural change (b) Fxc: a featural change across levels of a change in configuration.

88 75 [a] [b] Figure 3.19: Experiment 2: Inverted Trials: False alarm rate by age for: (a) Cxf: a change in configuration across levels of the featural change (b) Fxc: a featural change across levels of a change in configuration.

89 76 [a] [b] Figure 3.20: Experiment 2: Upright Trials: Hit rate by age for: (a) Cxf: a change in configuration across levels of the featural change (b) Fxc: a featural change across levels of a change in configuration.

90 77 [a] [b] Figure 3.21: Experiment 2: Inverted Trials: Hit rate by age for: (a) Cxf: a change in configuration across levels of the featural change (b) Fxc: a featural change across levels of a change in configuration.

91 78 [a] [b] Figure 3.22: Experiment 2: Upright Trials: Measures of response bias by age for: (a) Cxf: a change in configuration across levels of the featural change (b) Fxc: a featural change across levels of a change in configuration.

92 79 [a] [b] Figure 3.23: Experiment 2: Inverted Trials: Measures of response bias by age for: (a) Cxf: a change in configuration across levels of the featural change (b) Fxc: a featural change across levels of a change in configuration.

93 80 [a] [b] Figure 3.24: Experiment 2: Upright Trials: Measures of response bias by age for: (a) Cxf: a change in configuration across levels of the featural change (b) Fxc: a featural change across levels of a change in configuration.

94 81 [a] [b] Figure 3.25: Experiment 2: Inverted Trials: Measures of response bias by age for: (a) Cxf: a change in configuration across levels of the featural change (b) Fxc: a featural change across levels of a change in configuration.

95 Table 3.5: Experiment 2: UPRIGHT FACE ORIENTATION. Summary of marginal analyses and non-parametric test of sampling independence (SI) for each observer. Evidence Inference Group Observer Age Comparison MRI d c SI PI PS DS Children Conf feat T T T 0 T T T Feat conf T F T 0 T F T Conf feat T F T 0 T F T Feat conf T F T 0 T F T Conf feat F T F 0 T T F Feat conf F F T 0 T F? Conf feat T T T 0 T T T Feat conf T F T 0 T F T Conf feat T T T 0 T T T Feat conf T T T 0 T T T Conf feat T T T 0 T T T Feat conf T T T 0 T T T Conf feat T T T 0 T T T Feat conf T T T 0 T T T Conf feat T T T 0 T T T Feat conf T T T 0 T T T Conf feat F F T 0 T F? Feat conf T F T 0 T F T Conf feat F T F 0 T T F Feat conf F F F 0 T F? Conf feat T T T 0 T T T Feat conf T T T 0 T T T Conf feat T T T 0 T T T Feat conf T T T 0 T T T Conf feat T T T 0 T T T Feat conf T T T 0 T T T Conf feat T T T 0 T T T Feat conf T T T 0 T T T Adults Conf feat T F F 0 T T T Feat conf T F T 0 T F T Conf feat T T T 0 T T T Feat conf T T T 0 T T T Conf feat T T T 0 T T T Feat conf T T T 0 T T T Conf feat T T T 0 T T T Feat conf T T T 0 T T T Conf feat T T T 0 T T T Feat conf T T T 0 T T T Conf feat T T T 0 T T T Feat conf T T T 0 T T T Conf feat T F T 0 T F T Feat conf T T T 0 T T T Conf feat T F T 0 T F T Feat conf T T T 0 T T T Conf feat T T T 0 T T T Feat conf T T T 0 T T T Conf feat T T T 0 T T T Feat conf T T T 0 T T T Conf feat T T T 0 T T T Feat conf T T T 0 T T T Note: MRI = test of marginal response invariance; d = test of marginal sensitivity; c = test of marginal response bias; T = equality holds; F = equality does not hold; The number in the SI column indicates the total number of failures of SI. 82

96 Table 3.6: Experiment 2: INVERTED FACE ORIENTATION. Summary of marginal analyses and non-parametric test of sampling independence (SI) for each observer. Evidence Inference Group Observer Age Comparison MRI d c SI PI PS DS Children Conf feat T T T 0 T T T Feat conf T T T 0 T T T Conf feat T T T 0 T T T Feat conf F T T 0 T T T Conf feat F T F 0 T T F Feat conf T F T 0 T F T Conf feat F T F 0 T T F Feat conf T T T 0 T T T Conf feat T T T 0 T T T Feat conf T T T 0 T T T Conf feat T F T 0 T F T Feat conf T T T 0 T T T Conf feat T T T 0 T T T Feat conf T T T 0 T T T Conf feat T F T 0 T F T Feat conf T T T 0 T T T Conf feat T F T 0 T F T Feat conf F T T 0 T T T Conf feat T T T 0 T T T Feat conf T T T 0 T F T Conf feat T T T 0 T T T Feat conf T T T 0 T T T Conf feat T T T 0 T T T Feat conf T T T 0 T T T Conf feat F T F 0 T T F Feat conf F T T 0 T T T Conf feat T T T 0 T T T Feat conf T T T 0 T T T Adults Conf feat F F F 0 T F? Feat conf F F F 0 T F? Conf feat T T T 0 T T T Feat conf T T T 0 T T T Conf feat T T T 0 T T T Feat conf T T T 0 T T T Conf feat T T T 0 T T T Feat conf T T T 0 T T T Conf feat T T T 0 T T T Feat conf T T T 0 T T T Conf feat T T T 0 T T T Feat conf T T T 0 T T T Conf feat T F T 0 T F T Feat conf T F T 0 T F T Conf feat T F T 0 T F T Feat conf T T T 0 T T T Conf feat T T T 0 T T T Feat conf T T T 0 T T T Conf feat T T T 0 T T T Feat conf T T T 0 T T T Conf feat T T T 0 T T T Feat conf T T T 0 T T T Note: MRI = test of marginal response invariance; d = test of marginal sensitivity; c = test of marginal response bias; T = equality holds; F = equality does not hold; The number in the SI column indicates the total number of failures of SI. 83

97 84 Table 3.7: Experiment 2: Regression results and equations for sensitivity (d ), response bias (c), hit rates and false alarm rates. Measure Level Condition Line Type Group Significance Regression Equation Sensitivity (d ) Linear Regression C x f Upright Solid Line All Observers R 2 =.71, F (1, 23) = 55.41, p <.0001 y = 0.08x C x f Upright Dotted Line Children (ages 6-15) R 2 =.21, F (1, 12) = 3.25, p =.0967 y = 0.04x F x c Upright Solid Line All Observers R 2 =.65, F (1, 22) = 43.64, p <.0001 y = 0.08x F x c Upright Dotted Line Children (ages 6-15) R 2 =.44, F (1, 12) = 9.28, p =.01 y = 0.09x C x f Inverted Solid Line All Observers R 2 =.52, F (1, 23) = 25.02, p <.0001 y = 0.09x C x f Inverted Dotted Line Children (ages 6-15) R 2 =.15, F (1, 12) = 2.04, p =.179 y = 0.06x F x c Inverted Solid Line All Observers R 2 =.68, F (1, 23) = 48.43, p <.0001 y = 0.11x 0.36 F x c Inverted Dotted Line Children (ages 6-15) R 2 =.35F (1, 12) = 6.44, p =.0261 y = 0.10x 0.21 Response Bias (c) Linear Regression C x f Upright Solid Line All Observers R 2 =.0005, F (1, 23) =.01, p =.9160 y = 0.00x 0.05 C x f Upright Dotted Line Children (ages 6-15) R 2 =.18, F (1, 12) = 2.53, p =.1398 y = 0.02x 0.29 F x c Upright Solid Line All Observers R 2 =.0238, F (1, 23) =.56, p =.46 y = 0.00x F x c Upright Dotted Line Children (ages 6-15) R 2 =.01, F (1, 12) = 0.19, p =.67 y = 0.01x C x f Inverted Solid Line All Observers R 2 =.002, F (1, 23) =.02, p =.88 y = 0.00x 0.02 C x f Inverted Dotted Line Children (ages 6-15) R 2 =.07, F (1, 12) = 0.40, p =.6825 y = 0.01x 0.03 F x c Inverted Solid Line All Observers R 2 =.001, F (1, 23) =.02, p =.88 y = 0.00x F x c Inverted Dotted Line Children (ages 6-15) R 2 =.03, F (1, 12) = 0.38, p =.5479 y = 0.02x Response Bias (c) Quadratic Regression C x f Upright Solid Line All Observers R 2 =.0539, F (1, 22) = 1.25, p =.2748 y = 0.001x x.42 C x f Upright Dotted Line Children (ages 6-15) R 2 =.0119, F (1, 12) = 0.16, p =.6943 y = 0.003x 2.04x F x c Upright Solid Line All Observers R 2 =.04, F (1, 22) = 1.01, p =.3268 y = 0.001x 2.04x +.43 F x c Upright Dotted Line Children (ages 6-15) R 2 =.135, F (1, 12) = 0.16, p =.7012 y = 0.002x 2.06x C x f Inverted Solid Line All Observers R 2 =.09, F (1, 23) = 2.36, p =.14 y = x x 0.18 C x f Inverted Dotted Line Children (ages 6-15) R 2 =.24, F (1, 12) = 4.43, p =.06 y = 0.006x x 0.68 F x c Inverted Solid Line All Observers R 2 =.00, F (1, 24) =.25, p =.62 y = x 2.02x +.29 F x c Inverted Dotted Line Children (ages 6-15) R 2 =.43, F (1, 12) = 9.19, p =.01 y = 0.02x x 1.54 Hit Rates Linear Regression C x f Upright Solid Line All Observers R 2 =.46, F (1, 23) = 19.92, p =.0002 y = 0.008x C x f Upright Dotted Line Children (ages 6-15) R 2 =.00, F (1, 12) = 0.00, p =.986 y = x F x c Upright Solid Line All Observers R 2 =.4085, F (1, 23) = 15.89, p =.0006 y = 0.01x F x c Upright Dotted Line Children (ages 6-15) R 2 =.36, F (1, 12) = 6.80, p =.0229 y = 0.02x C x f Inverted Solid Line All Observers R 2 =.12, F (1, 24) = 3.33, p =.08 y = 0.01x C x f Inverted Dotted Line Children (ages 6-15) R 2 =.00, F (1, 12) = 0.04, p =.84 y = x F x c Inverted Solid Line All Observers R 2 =.02, F (1, 24) = 0.45, p =.51 y = 0.02x F x c Inverted Dotted Line Children (ages 6-15) R 2 =.12, F (1, 12) = 1.70, p =.22 y = 0.03x False Alarm Rates Linear Regression C x f Upright Solid Line All Observers R 2 =.54, F (1, 23) = 26.92, p <.0001 y =.01x C x f Upright Dotted Line Children (ages 6-15) R 2 =.354, F (1, 12) = 6.58, p =.0248 y = 0.02x F x c Upright Solid Line All Observers R 2 =.58, F (1, 23) = 31.73, p =.0001 y = 0.01x F x c Upright Dotted Line Children (ages 6-15) R 2 =.21, F (1, 12) = 3.22, p =.10 y = 0.01x C x f Inverted Solid Line All Observers R 2 =.46, F (1, 23) = 19.78, p =.0002 y = 0.01x C x f Inverted Dotted Line Children (ages 6-15) R 2 =.15, F (1, 12) = 2.08, p =.17 y = 0.01x F x c Inverted Solid Line All Observers R 2 =.41, F (1, 23) = 16.07, p =.0006 y = 0.02x F x c Inverted Dotted Line Children (ages 6-15) R 2 =.14, F (1, 12) = 1.90, p =.19 y = 0.02x

98 General Discussion and Conclusions The present study is the first to use three representations of holism derived from general recognition theory (Ashby & Townsend, 1986) to test for evidence of developmental changes in face perception. The first notable finding was a pattern of violations in the GRT constructs that was similar for adults and children in both of the experiments. Specifically, adults and children both showed a pattern of violations in DS and PS with no violations in PI in both experiments, which suggests they encoded face information in a qualitatively similar manner. It also suggests adults and children encoded the dimensions of composite face stimuli and changes in the facial features and the relative configurations of upright and inverted stimuli independently at the level of an individual stimulus. This is evidence supporting the assumptions of the dual-mode hypothesis and evidence against the holistic encoding hypothesis. The second notable finding was a significant age-related increase in measures of sensitivity (d ) and a significant decrease in false alarm rates in both experiments. This is evidence of quantitative improvements in face perception across development. It is also possible these quantitative changes could reflect the development of more general cognitive abilities such selective attention and response inhibition Holistic versus Independent Encoding The holistic encoding hypothesis is a well-known contemporary account of face perception that suggests adults encode faces holistically, as unitary perceptual wholes. Developmental studies of holistic encoding using part-whole (Pellicano & Rhodes, 2003; Pellicano, Rhodes & Peters, 2006; Tanaka, Kay, Grinnell, Stansfield & Szechter, 1998) and composite face tasks (Pellicano & Rhodes, 2003; Pellicano, Rhodes & Peters, 2006; Tanaka, Kay, Grinnell, Stansfield & Szechter, 1998) suggest that children also encode face information holistically. Further, these studies report holistic encoding appears to be mature in children as young as age three and suggest there is no evidence of a developmental change in holistic encoding. An assumption of another well-known account of face perception, the dual-mode hypothesis (Searcy & Bartlett, 1996), stands in contrast to the holistic encoding account of face perception. This alternative account suggests face information is encoded in terms of two independent sources of face information rather than as a gestalt. It suggests one source of encoded face information is information about the spatial relations of the facial features (e.g., distance from the nose to the eyes) and the second source of information is information about the physical characteristics of the features (e.g, color of eyes and size of nose). Developmental studies of face perception have tested the dual-mode account of face perception quite frequently over the last three decades. Contrary to developmental studies of holistic encoding, studies testing for differences in encoding featural and configural face information have often reported evidence of developmental changes in face perception. This

99 86 evidence has then been subsequently interpreted with respect to developmental changes in the mechanisms thought to underlie differences in performance on face perception tasks. One significant limitation of previous studies is the wide range of operational definitions they have used to presumably represent the same constructs. There is also concern that the measures they have used to assess developmental changes were often not linked to a theoretical framework that supported exhaustive tests of an alternative set of hypotheses. These limitations makes it difficult to link age-related differences in performance on face perception tasks to clear inferences of changes in the mechanisms underlying encoding that occur across development. The inability to make a clear connection between different patterns in performance to theory has led to several competing hypotheses that attempt to link differences in performance to changes in the mechanisms underlying face perception Connections Between Theory and Data A review of the literature suggests the study of face perception could benefit from an approach that provides rigorous tests of developmental differences that are clearly linked to theoretical interpretations. The theoretical constructs and statistical tests provided by general recognition theory offer one such approach. In addition to using the constructs and measures provided by GRT, the two experiments in the present study were performed (primarily, see Table 4.1) within-subjects using the same base set of face stimuli. This approach to experimentation allowed a stronger comparison to be made between the results of the two face perception tasks. Holistic Encoding Hypothesis A point of debate in the face perception literature is whether adults and children encode face information dependently or independently. One line of work testing the holistic encoding hypothesis reports that children and adults both process faces as integral, perceptual wholes. This line of work also suggests the ability to encode face information matures early and that there are no changes in the ability to encode face information across development. The present study tested the assumptions of the holistic encoding hypothesis using a composite face identification experiment. Both qualitative and quantitative developmental changes in encoding face stimuli were assessed using GRT measures and measures of sensitivity (d ), response bias (c), hit rates and false alarms. The pattern of GRT results for adults and children showed violations in PS and DS with no violations in PI. A pattern of results with violations in PI for children and adults would be the strongest evidence in favor of the holistic encoding hypothesis. It would suggest dependencies exist in the representation of face information at the level of an individual stimulus. The fact that there were no violations and that equality held for PI in all instances for all observers provides strong evidence

100 87 against the holistic encoding hypothesis for adults and children. It suggests children and adults encoded the dimensions of the composite face information independently at the level of an individual stimulus. Although there were no violations in PI, there were violations in PS and DS for adults and children. To some extent violations in PS and DS can be interpreted as evidence supporting the holistic encoding with one concession. Violations in these constructs is evidence of perceptual dependencies occurring across all composite face stimuli and at the level of shifts in response criteria rather than at the level of an individual composite face stimulus. An assessment of the presence and pattern of violations in PS and DS for adults and children suggested that children and adults encoded the composite face stimuli in a qualitatively similar manner. First, adults and children showed no instances of violations in PI. Second, both adults and children showed instances in which PS and DS were violated and instances in which equality held for one or both constructs. While the pattern of GRT analyses suggest children and adults encoded face information in a qualitatively similar manner, regression analyses provided evidence of quantitative developmental changes in face perception. There was a significant age-related increases for values of sensitivity (d ) primarily driven by a significant decrease in false alarm rates with age. Dual-Mode Hypothesis A second line of work in the developmental face perception offers a perspective of encoding that competes with the perspective of the holistic encoding hypothesis. This line of work is based on an assumption of the dual-mode hypothesis. It suggests that face information is encoded in terms of two independent sources of information (i.e., configural and featural information). In contrast to developmental studies of the holistic encoding hypothesis, developmental studies emerging from this line of work have frequently reported developmental changes in encoding. The present study tested the assumption that configural and featural information are processed as independent sources of face information using an inversion face task. The pattern of GRT results for adults and children showed violations in PS and DS with no violations in PI. A pattern of results with no violations in PI for children and adults (i.e. instances in which equality held) would be the strongest evidence in favor of the dual-mode hypothesis. It would suggest changes in configural and featural information are encoded independently at the level of an individual stimulus. The fact that there were no violations in PI and equality held for PI in all instances for all observers provides support for the dual-mode hypothesis. It is strong evidence that adults and children encoded changes in featural and configural information independently at the level of the individual stimulus. There was a pattern of violations in PS and DS for children and adults in the upright and inverted face conditions that was similar to the pattern of violations reported in the composite face task. Specifically, there were instances in which PS and DS were

101 88 violated for some of the adult and child observers and instances in which equality held for one or both constructs. This is evidence that children and adults encoded face information in a qualitatively similar manner in both upright and inverted conditions. Regression analyses also provided evidence of quantitative developmental changes in face perception that were similar to the changes reported in the composite face study. There was a significant age-related increases for values of sensitivity (d ) primarily driven by a significant decrease in false alarm rates with age General Cognitive Functioning The present study showed a similar pattern of age-related changes in encoding face information across two face perception tasks. The pattern of GRT results in each experiment suggested children and adults encoded face information in a qualitatively similar manner. There was also evidence an age-related quantitative increase in sensitivity (d ) that appeared to be driven by an age-related decrease in false alarm rates in both experiments. Rather than reflecting developmental changes that are specific to encoding face information, the similarity in the patterns of results across experiments suggests they might reflect developmental changes in more general cognitive functions. Although this study does not provide overt information about the mechanisms underlying quantitative changes in sensitivity and false alarm rates, it does provide the groundwork for hypotheses to test potential mechanisms. Two potential mechanisms that might account for the quantitative age-related changes in sensitivity and false alarm rates in the present study are selective attention and response inhibition. Selective Attention Selective attention refers to the ability to attend to relevant information while filtering out irrelevant information. Several studies have reported improvements in selective attention across childhood, which have been linked to the maturation of frontal regions of the brain (Plude, Enns & Brodeur, 1994; Ridderinkhof & vanderstelt, 2000). It is possible that the age-related increases in sensitivity and decreases in false alarm rates reported in the present study could reflect developmental changes in selective attention. Following this interpretation, sensitivity increases and false alarm rates decrease as attentional networks mature and the ability to attend to relevant information and filter out irrelevant information improves with development. This explanation would be consistent with findings from a recent study that reported developmental improvements in selective attention and related these improvements to the ability to selectively attend to face identity while ignoring face expression (Baudouin, Durand & Gallay, 2008). It also leads to questions about the relationship between age-related increases in sensitivity and changes in the mechanisms that underlie

102 89 selective attention. According to the load theory of selective attention (Lavie, Hirst, Fockert & Viding, 2004), there are two mechanisms underlying selective attention. The first is a passive mechanism that reduces distractor perception in cases of high perceptual load that exhaust processing capacity. The second mechanism reduces interference from perceived distractors when capacity is still available (low perceptual load). A recent study by Von Der Heide, Wenger and Gilmore (2008) reported a shift from a limited capacity to process face information in early childhood (age 6) to an unlimited or super-capacity to process face information adulthood (age 25). One question to explore in future work is whether age-related increases in processing capacity (VonDerHeide, Wenger & Gilmore, 2008) and the age-related increases in sensitivity to face information reported in the present study could both be driven by the maturation of one or more mechanisms underlying selective attention. Response Inhibition In addition to selective attention, the age-related increases in sensitivity and decreases in false alarm rates in the present study might also reflect a developmental change in response inhibition. One account of response inhibition defines it as the ability to inhibit incorrect or prepotent responses. A second account known as the inefficient inhibition model defines inhibition as the competitive interaction between two processes rather than the active suppression of processes (Bjorklund & Harnishfeger, 2008). Both accounts suggest response inhibition follows a a protracted time-course of development across childhood and relate improvements in this mechanism to the maturation of the prefrontal cortex (PFC) (Diamond, 1988; Dempster, 1992). It is possible that the increases in sensitivity and decreases in false alarm rates in the present study could be related to a change in the efficiency of inhibitory processes during childhood. As inhibitory processes become more efficient, they allow less irrelevant information to enter working memory and increase the capacity to process face information. Perhaps, an age-related decrease in the irrelevant information in working memory and an increase in capacity to process face information can be associated with the age-related increase in sensitivity to face information reported in the present study. Another question to explore in future work is whether increases in the capacity to process face information (VonDerHeide, Wenger & Gilmore, 2008) and the increases in sensitivity reported in the present study could be driven by the maturation and greater efficiency of inhibitory processes Conclusions and Future Directions The present study provided evidence of quantitative rather than qualitative changes in the ability to encode face information across development. Results from two face perception

103 90 tasks showed signficant age-related increases in sensitivity (d ) to face information, which appeared to be driven by an age-related decrease in false alarm rates. One goal of future studies should be to explore whether the age-related increases in sensitivity reported in the present study might be related to developmental changes in more general cognitive functions such as selective attention or response inhibition. Both selective attention and response inhibition show a protracted time-course of development across childhood. It is possible that changes in one or both of these cognitive functions could account for the agerelated quantitative changes in sensitivity reported in the present study. In addition, this line of future work should investigate the relationship between developmental changes in the capacity to process and the ability to encode face information in order to determine if and how changes in both can be related to developmental changes in more general cognitive functions. In addition to providing evidence of quantitative developmental changes in face perception, the present study provided clear evidence in favor of the assumptions of the dual-mode hypothesis and against assumptions of the holistic encoding hypothesis. The results from GRT analyses suggested the dimensions of composite, upright and inverted faces were all encoded independently at the level of an individual stimulus. While there was evidence of dependencies between the dimensions of face stimuli, these dependencies occurred across all presentations of the stimuli and at the level of interactions of the response criteria rather than at the level of the individual stimulus. It was at the level of the individual stimulus that both the dual-mode and holistic encoding hypothesis made competing predictions about the independent versus dependent encoding of face information. Future work should check whether violations of PI, DS and PS are capable of producing the congruency (experiment 1) and inversion (experiment 2) effects. The purpose of these checks is to determine whether the data obtained from GRT analyses reveal more than the congruency or inversion effect alone. For example, if the congruency or inversion effect emerged only in instances when there were violations of PS then GRT analyses would not provide any information in addition to these effects. Richler et al. (2008) provided this type of check using Monte Carlo Simulations in a composite face study of adult participants. They found both violations of PS and violations of DS produce significant congruency effects and that GRT analyses were necessary in order to understand the perceptual or decisional sources of holism underlying this effect. Another goal of future studies should be to evaluate how the nature of face perception tasks such as the composite face and inversion face tasks restrict the generality of component processes of face processing. It is possible that the specific demands of the experimental tasks used in the present study result in a specific set of outcomes, which might change with variations in the demands of the experimental task. Finally, future work should evaluate whether the nature of the face stimuli had an effect on the pattern of results in the current study. Participants in the current study performed

104 91 face perception tasks using face stimuli of college-age individuals. There is some evidence supporting an own-age bias for children on face perception tasks. Specifically, Anastasi and Rhodes (2005) reported significantly higher sensitivity (d values) for children when they were asked to recognize the faces of children in their own age group compared to faces of older adults. Adults showed a similar shift with greater sensitivity (i.e., higher d values) when they were asked to recognize faces of adults compared to children. They suggested this increase in sensitivity for individuals in the same age-group could be the product of familiarity or perhaps, differences in processing strategies for individuals in the same age-group. Future studies should investigate whether the age-related quantitative shifts in sensitivity in the current study could be explained by differences in familiarity or processing strategies for individuals across different age groups.

105 92 Chapter 4 Appendices Figure 4.1: Experiment 1: Morphing: Dimension AB Figure 4.2: Experiment 1: Morphing: Dimension AC

106 93 Figure 4.3: Experiment 1: Morphing: Dimension AD Figure 4.4: Experiment 1: Morphing: Dimension BC Figure 4.5: Experiment 1: Morphing: Dimension BD