Congruency as a Nonspecific Perceptual Property Contributing to Newborns Face Preference

Transcription

1 Child Development, July/August 2008, Volume 79, Number 4, Pages Congruency as a Nonspecific Perceptual Property Contributing to Newborns Face Preference Viola Macchi Cassia University of Milano-Bicocca Eloisa Valenza, Francesca Simion, and Irene Leo University of Padova Past research has shown that top-heaviness is a perceptual property that plays a crucial role in triggering newborns preference toward faces. The present study examined the contribution of a second configural property, congruency, to newborns face preference. Experiments 1 and 2 demonstrated that when embedded in nonfacelike stimuli, congruency induces a preference of the same strength as that induced by facedness. Experiments 3 and 4 demonstrated that the attentional biases toward facedness and congruency produce a cumulative effect on newborns visual preferences according to an additive model. These findings were extended by those of Experiment 5, showing that the additive model holds true when congruency is added to top-heaviness in nonfacelike stimuli displaying more elements in the upper portion. Face recognition in human adults is considered to be a sophisticated and specialized ability. This is because faces are highly complex visual stimuli whose processing involves specific brain regions (Kanwisher, McDermott, & Chun, 1997; Sergent, Ohta, & MacDonald, 1992) and specialized perceptual strategies (see Peterson & Rhodes, 2003, for a review). This specialized response toward faces has sparked debates as to whether specialization may be innate and specific to faces (e.g., Farah, Rabinowitz, Quinn, & Liu, 2000) or may be acquired through the extensive experience individuals acquire with faces within the human species-specific environment (expertise hypothesis; Diamond & Carey, 1986; Gauthier & Tarr, 1997, 2002). Central to this debate is evidence provided by developmental literature showing that just a few days after birth, when visual experience with faces is still minimal, newborns visual attention is preferentially attracted toward both schematic facelike configurations (Johnson & Morton, 1991; Mondloch et al., 1999; Valenza, Simion, Macchi Cassia, & Umiltà, 1996) and veridical face images This research was supported by a grant from the Ministero dell Università e della Ricerca (No ) and a grant from the University of Milano-Bicocca (Fondi di Ateneo per la Ricerca 2004). The authors are deeply indebted to Dr. B. Dalla Barba and the nursing staff at the Pediatric Clinic of the University of Padova and Dr. M.E. Sotti and the nursing staff at the Casa di Cura of Abano Terme for their collaboration. The authors also thank Dana Kuefner for her thoughtful contribution to the creation of stimuli for Experiment 5, and Stefano Vezzani for his advice concerning the adult visual perception literature. Correspondence concerning this article should be addressed to Viola Macchi Cassia, Department of Psychology, University of Milano-Bicocca, via dell Innovazione 10, U9, Milano, Italy. Electronic mail may be sent to viola.macchicassia@unimib.it. (Macchi Cassia, Turati, & Simion, 2004), as compared to equally complex nonfacelike configurations. There is little dispute that this initial attentional bias toward faces triggers the development of neurocognitive specialization for this class of stimuli, as it results in biased input being provided to the developing cortical tissues within the ventral visual cortex. As a benefit from their frequent exposure to faces, these cortical circuits become progressively structurally and functionally specialized for the processing of stimuli that fall within the face category (Johnson, 2000). Support for this view comes from studies on the effects of early visual deprivation. These studies show that when the face bias cannot exert its influence from birth, as in individuals born with dense bilateral cataracts, face recognition abilities follow an abnormal developmental trajectory (Geldart, Mondloch, Maurer, de Schonen, & Brent, 2002; Le Grand, Mondloch, Maurer, & Brent, 2001). However, controversy remains about the basis of the newborns face bias. According to the model of the development of face processing originally proposed by Johnson and Morton (1991) and more recently updated by Johnson (2005), newborns attention is triggered by faces due to the rapid and automatic activation of a face-configuration detector (i.e., Conspec). This face detector is supported by a fast subcortical processing route operating on low-spatial frequencies, which selectively responds to stimuli consisting of a raised surface with darker areas corresponding to the approximate locations of eyes # 2008, Copyright the Author(s) Journal Compilation # 2008, Society for Research in Child Development, Inc. All rights reserved /2008/

2 808 Macchi Cassia, Valenza, Simion, and Leo and mouth. An alternative view, which has recently received much attention within the field, proposes that newborns face preference arises from a number of domain-general perceptual biases that drive newborns attention toward certain structural properties of visual stimuli (Simion, Macchi Cassia, Turati, & Valenza, 2001, 2003; Turati, 2004). It has been proposed that these nonspecific biases may likely derive from the functional properties of the newborn s visual system and have a priori nothing to do with faces. Rather, they are domain relevant, allowing newborns to successfully select faces among other nonfacelike stimuli within their species-typical environment. This claim derives mainly from two lines of reasoning. First, it has been shown that in addition to facedness, newborns manifest spontaneous preferences for other structural properties of visual stimuli (Farroni, Valenza, Simion, & Umiltà, 2000; Simion, Valenza, Macchi Cassia, Turati, & Umiltà, 2002; Slater, Earle, Morison, & Rose, 1985). Therefore, facedness is not the only stimulus dimension that is capable of triggering infants attention at birth. Second, faces themselves can be described as a collection of perceptual properties. Therefore, the possibility exists that some, if not each of these properties, plays a role in prompting the newborns attentional response toward facelike stimuli. Until now, research has focused on one of the structural properties embedded in faces, namely, top-heaviness. Faces can be described as top-heavy stimuli because they display a greater amount of patterning the eyes and eyebrows in the upper portion, and a lesser amount the mouth in the lower portion. A series of studies have shown that when embedded in geometric nonfacelike stimuli, the top-heavy property is capable of inducing a preferential visual response in newborns (Simion et al., 2002). This preferential response has been related to a difference in sensitivity between the upper and the lower visual field, similar to the upper visual field advantage observed in adults (Rubin, Nakayama, & Shapley, 1996; Skrandies, 1987), which would render top-heavy patterns more easily detectable than other stimuli. The key finding from these studies, obtained using both schematic (Turati, Simion, Milani, & Umiltà, 2002) and veridical (Macchi Cassia et al., 2004) face images, is that newborns attend equally long to a face as to a perceptually similar nonface stimulus that shares with the face a top-heavy distribution of the features within the outer contour. This demonstration that the facelike arrangement of the inner features displayed by the face did not selectively affect newborns visual behavior was taken as evidence that what is classically interpreted as a specific inborn preference for the face geometry is likely the result of a more general preference for top-heavy visual objects. Indeed, stimuli within this category include but are not limited to faces. In the present study, we investigated the contribution to the face preference phenomenon of a second configural visual property included in faces, which we refer to as congruency. Congruency can be defined, in any given pattern, by the presence of a congruent or corresponding relationship between the shape and the orientation of the bounded area delimiting the pattern and the spatial disposition of the included features. Although the congruency property could be much easily detected in abstract, geometric configurations than in realistic images of real-life visual objects, faces indeed can be described as congruent stimuli. Despite within-category variability in perceptual appearance, faces on average are delimited by a mono-oriented frame, which appears wider in the upper part where the hair and ears are located and narrower in the lower part where the chin and the neck are located. Therefore, given the typical spatial arrangement of the eyes and mouth, faces display a greater number of features in the widest portion and only one feature in the narrowest part. Following the same logic used in earlier studies investigating the contribution of the top-heavy bias to newborns face preference, we reasoned that if the congruency property is capable of inducing a preferential response when embedded in nonfacelike configurations, then it could be argued that this property also plays a role in inducing newborns preference for faces. The hypothesis that congruent visual configurations may be preferred at birth over noncongruent patterns appears reasonable in light of three lines of research. First, there is considerable evidence that newborns are highly sensitive to configural holistic properties emerging from the interrelations between the component parts of the stimuli. For instance, they can perceive the invariance of the spatial relationship between single features, which vary in their absolute position within an array (Antell, Caron, & Myers, 1985). Also, newborns are able to group separate sets of elements according to Gestalt principles (Farroni et al., 2000), and they find configural and global cues in hierarchical patterns more easily detectable than featural and local information (Macchi Cassia, Simion, Milani, & Umiltà, 2002). Second, based on Gestalt theories of visual perception (Garner, 1974; Palmer, 1991), in comparison to noncongruent configurations, congruent configurations provide a better fit for the criteria of figural simplicity and regularity that render visual patterns more easily and economically processed and represented by the human perceptual

3 A Nonspecific Property Contributing to Newborns Face Preference 809 system. Because newborns have been shown to perceive and organize visual arrays according to Gestalt principles, such as lightness similarity (Farroni et al., 2000) and common motion (Valenza & Bulf, 2007), it seems reasonable to hypothesize that newborns may also be sensitive to other stimulus dimensions that contribute to figural goodness, such as symmetry, repetition, and regularity. Each of these dimensions is maximally present in congruent visual configurations. Third, preliminary findings from an exploratory visual preference study showed that when newborns were presented with a 180 rotated version of the schematic facelike and nonfacelike configurations used in earlier face preference studies, they did not show a preferential response for either of the two stimuli (p 5.2; Macchi Cassia, Valenza, and Simion, unpublished data; Figure 1). A possible interpretation of this finding is that each of the stimuli contained a relevant property, that is, top-heaviness or congruency, and that these two properties competed in triggering newborns attention. Indeed, being upside down, the schematic face displayed a congruent relationship between the orientation of the outer border and the spatial locations of the included elements (i.e., two elements were located in the widest portion of the border) in the absence of a top-heavy arrangement of those elements (i.e., two elements were located in the lower part of the triplet and one in the upper part). In contrast, the rotated nonfacelike stimulus displayed a noncongruent relation between the border and the inner elements in the presence of a top-heavy arrangement of those elements. Therefore, newborns may have failed to show a preference for either of the two stimuli as a consequence of the competing properties embedded in the stimuli. In the present study, we aimed to test the role played by the perceptual property of congruency in newborns face preference. To do so, we used the same approach that was used in previous studies investigating the role of the top-heavy property in newborns face preference. The rationale of those studies was that of altering the spatial integrity of the facelike configuration so as to selectively break one of the structural rules embedded in faces and testing the effect of each manipulation on newborns visual preferences. The same systematic approach of decomposing the structural properties defining facedness was applied in the present study, where we measured newborns attentional responses to compound geometric stimuli in which we independently manipulated the facelike versus nonfacelike arrangement of the inner elements and the congruent versus noncongruent relation of the elements with the shape of the external contour. It is important to note that in the facelike stimuli used in Experiments 1 through 4, the facedness and the top-heavy property were inextricably mixed, and therefore, we refer to those stimuli as facelike and make reference to facedness as the crucial property defining those stimuli. In the stimuli used in Experiment 5, the number and shape of the inner elements and the spatial integrity of the facelike configuration were altered. Therefore, we refer to those stimuli as nonfacelike top-heavy and make reference to top-heaviness as the crucial property defining them. In the five reported experiments, newborns were tested using a preferential looking paradigm. The specific aims of the experiments were (a) to determine whether the congruency property elicits a preference when it is embedded in nonfacelike stimuli (Experiment 1); (b) to test the relative strength of congruency and facedness in eliciting newborns preference (Experiment 2); (c) to test the hypothesis of an additive model, where facedness and congruency contribute to the same extent to trigger newborns attention toward faces (Experiments 3 and 4); and (d) to extend the validity of the additive model when congruency is added to top-heaviness in nonfacelike stimuli displaying more elements in the upper portion (Experiment 5). Figure 1. The 180 rotated version of the schematic facelike and nonfacelike configurations used in the exploratory visual preference study. Note. Newborns did not show a preferential response for either of the two stimuli (Macchi Cassia, Valenza, and Simion, unpublished data). Experiment 1 The aim of the first experiment was to provide evidence as to whether newborns show a spontaneous visual preference for congruent over noncongruent nonfacelike visual configurations. To test this hypothesis, newborns were presented with two compound stimuli comprising three black squares embedded

4 810 Macchi Cassia, Valenza, Simion, and Leo in a triangular-shaped area. The orientation of the triangular-shaped areas was either congruent or noncongruent with the spatial arrangement of the inner elements (Figure 2). The spatial arrangement of the three squares was analogous to that used in the inverted nonfacelike stimuli employed in the studies of Johnson and Morton (1991) and Valenza et al. (1996), showing newborns preference for schematic faces. Method Participants. The participants were 12 (5 males) healthy, full-term infants, hr old, recruited from the maternity wards of the Pediatric Clinic at the University of Padova and the Gynecology Unit at the Hospital of Abano Terme. They were middle-class infants, and 99% of them were Caucasian and 1% was Asian. Two additional infants were tested, but one did not complete testing due to fussiness and one was excluded from the data analysis due to position bias (i.e., looking more than 80% of the time in one direction). Infants were tested only in an awake, alert state, after the parents had given their informed consent. Stimuli. Each stimulus comprised three black square elements that were 2.2 cm (4.2 ) on each side and located into a white triangular-shaped area that was 13.5 cm (24.2 ) in width and 15 cm (26.6 ) in height. The squared elements were arranged in a nonfacelike disposition, with two elements in the lower part and one in the upper part, so as to create a triangle with one vertex pointing up. The distance between the three elements was 1 cm (1.9 ). The two stimuli were identical except for the orientation of the white area, which paralleled the orientation of the triangle created by the three inner elements with one vertex pointing up in the congruent stimulus, and rotated 180 so that the vertex was pointing down in the noncongruent stimulus (Figure 2). Apparatus. The infant sat on a student s lap, in front of a black panel, at a distance of about 30 cm. The panel had two square holes where the black screens of two computer monitors appeared. The infant s eyes were aligned with a red flickering light emitting diode (LED), located in the center of the screen. The LED was used to attract the infant s gaze at the start of both the habituation and the preference test phases, subtended about 2 of a visual angle and, when turned on, blinked at a rate of 300 ms. Stimuli were projected bilaterally at a distance of approximately 7 cm from the central LED. To prevent interference from irrelevant stimuli, two black panels were placed on both sides of the infant to limit peripheral vision. Figure 2. Stimulus pairs and results from Experiments 1, 2, and 3. Note. For each experiment, two graphs are reported. The first graph shows the total fixation time toward each stimulus, with error bars indicating standard deviations. The second graph shows the number of newborns who oriented more frequently and/or looked longer toward each stimulus. For each graph, the p value is reported for the comparison between the stimuli. *p,.05. **p,.01. yp 5.07.

5 A Nonspecific Property Contributing to Newborns Face Preference 811 Procedure. Each trial began with the central flickering LED. As soon as the infant fixated the LED, an experimenter started the sequence of trials by pressing a key on the computer keyboard. This automatically turned off the central LED and activated the stimuli on the screens. Stimuli remained on as long as the infant fixated one of them (i.e., infant control procedure). When the infant shifted his gaze from the display for more than 10 s, the experimenter turned off the stimuli and the central LED automatically turned on. All infants were presented with two trials, in which the position of the stimuli was counterbalanced. All testing sessions were video recorded. Videotapes of eye movements throughout the trial were subsequently analyzed frame by frame to the nearest 40 ms by two coders, both unaware of the stimuli presented. The coders recorded number of orienting responses toward the stimuli and total fixation times, that is, the sum of all fixations (Cohen, 1972, 1973). Intercoder agreement (Pearson correlation) was.99 for total fixation time and.91 for discrete number of looks. Results Preliminary analyses of variance (ANOVAs) showed no significant main effects or interactions involving the within-subjects factor of trial (first or second) for either dependent variable. Therefore, two separated t tests for dependent samples were performed to compare number of orienting responses and total fixation time to the congruent and the noncongruent stimulus. Newborns showed a nonsignificant trend to orient more frequently to the congruent pattern (M , SD 5 5.4) rather than to the noncongruent pattern (M , SD 5 6.3), t(11) , p This trend reached statistical significance for total fixation times, which were 22% longer to the congruent stimulus (M s, SD ) than to the noncongruent stimulus (M s, SD ), t(11) , p (both tests were two-tailed; Figure 2). Finally, we examined the data for individual infants and compared the number of infants who oriented more frequently and/or looked longer at the congruent stimulus than at the noncongruent stimulus. The comparisons were performed by means of two different statistical tests: a binomial test and a nonparametric Wilcoxon signed-rank test, which was used in consideration of the small sample numerosity. Eight of 10 infants (2 infants were not included in the count because they produced the same number of looks to the two stimuli) made a greater number of looks to the congruent stimulus (8 vs. 2, binomial test p and Wilcoxon test p 5.092), and 11 of 12 infants looked longer at the congruent stimulus (11 vs. 1, binomial test p and Wilcoxon test p 5.012; Figure 2). The difference in looking times for the two stimuli ranged from 11.9 to s. Discussion The results showed that the presence of a congruent relation between the shape and the orientation of the bounded area delimiting the pattern and the spatial disposition of the included features is one of the stimulus properties that control newborns visual preferences. The two stimuli used in the present experiment contained the same amount of visual information, displayed the same symmetrical configuration, and neither resembled a face in that the spatial disposition of the inner elements did not simulate the face geometry. Rather, the stimuli differed exclusively in the orientation of the triangularshaped contour and, therefore, in the congruent versus noncongruent relation between the contour and the triplet of inner elements. Therefore, congruency can be regarded as the crucial factor that produced the observed preference. This finding proves particularly relevant because it provides the first demonstration of the presence in newborns of a spontaneous attentional bias toward a configural/relational perceptual property, that is, a property emerging from the spatial interrelations among the stimulus components (Kimchi, 1992). Most crucially, the demonstration that the congruent relation between the disposition of the inner elements and the shape of the external contour is capable of triggering newborns attention when embedded in nonfacelike configurations raises the possibility that this same property may also play a role in triggering newborns attention toward facelike stimuli. The spontaneous preference for the congruency property may be a contributing factor that, interacting with other factors, gives rise to the newborns face preference phenomenon. This possibility was explored in the following experiments. Experiment 2 To explore the strength of the congruency property in prompting newborns attentional responses to facedness, in Experiment 2, the nonfacelike congruent stimulus preferred in Experiment 1 was contrasted to a noncongruent stimulus displaying a facelike arrangement of the inner elements (Figure 2). The facelike spatial arrangement of the triplet of elements in the noncongruent stimulus was analogous to that used in the upright facelike stimuli

6 812 Macchi Cassia, Valenza, Simion, and Leo employed in the studies of Johnson and Morton (1991) and Valenza et al. (1996), showing newborns preference for schematic faces. A preference for either of the two stimuli would indicate which of the two stimulus properties (i.e., facedness vs. congruency) is more influential in driving newborns attention. Crucially, if newborns would not manifest a preference, this would imply that none of the two properties is more powerful than the other in triggering attentional responses at birth. Method Participants. The final sample consisted of 16 (10 males) healthy, full-term, middle-class, Caucasian infants, hr old. Four additional infants were tested but not included in the sample because of fussiness (n 5 2) or position bias (n 5 2). Stimuli. The stimuli in this experiment were the congruent nonfacelike pattern presented in Experiment 1 and a noncongruent facelike pattern, which was matched to the congruent pattern for the orientation of the white area and differed exclusively for the spatial disposition of the three inner elements (Figure 2). In both stimuli, the triangular-shaped white area had one vertex pointing up. In the facelike stimulus, two elements of the triplet were located in the upper part of the configuration and one in the lower part, whereas in the nonfacelike stimulus, the triplet of elements was rotated 180 so that two elements appeared in the lower part and one in the upper part. Apparatus and procedure. The same apparatus and procedure from Experiment 1 were used. Results Preliminary ANOVAs showed no significant main effects or interactions involving the within-subjects factor of trial (first or second) for either dependent variable. Two paired-sample t tests were performed to determine whether newborns number of orienting responses and total fixation time differed for the two stimuli presented. The difference was not significant for either dependent variable (Figure 2). Newborns looked 14.9 (SD 5 6.7) times at the noncongruent facelike stimulus and 16.2 (SD 5 9.3) times at the congruent nonfacelike stimulus, t(15) , p Similarly, they spent 96.2 s (SD ) and 97.5 s (SD ) looking at the noncongruent and congruent stimuli, respectively, t(15) , p (both tests were two-tailed). Finally, examination of the data for individual infants revealed that the number of infants who produced a greater number of looks and/or looked longer at the noncongruent facelike stimulus did not differ from the number of infants who oriented more frequently toward (6 vs. 10, binomial test p and Wilcoxon test p 5.242) and/or fixated longer (8 vs. 8, binomial test p and Wilcoxon test p 5.717) the congruent nonfacelike stimulus (Figure 2). The difference in looking times for the two stimuli ranged from 14.8 to s. Discussion Although nonsignificant results should be interpreted with caution, these findings seem to suggest that facedness per se was not the only factor affecting newborns preferences in the present experiment. The absence of a preference for either stimulus likely indicates that facedness and the configural property of congruency contributed to the same extent to drive newborns preferences. These findings confirm and extend the null results obtained in the exploratory study with 180 rotated schematic facelike and nonfacelike stimuli (Macchi Cassia, Valenza, and Simion, unpublished data; Figure 1), providing further evidence that when facedness and congruency are pitted against each other, these two stimulus properties evoke a competition for newborns attentional resources. The result is a failure for newborns to show a preference for either stimulus. The demonstration that the preference for the congruent stimulus was not overcome by the preference for the facelike stimulus lands support to the hypothesis that both stimulus properties congruency and facedness may play a role in inducing newborns preference for faces, given that both are properties defining the face stimulus category. More specifically, the lack of any significant result in Experiment 2 might support the hypothesis that the attentional biases toward facedness and congruency produce a cumulative effect on newborns visual preferences according to an additive model, in which both biases would exert an equally critical influence on newborns preferential responses. Experiment 3 The aim of Experiment 3 was to provide a direct test of the additive role of facedness and congruency in inducing newborns preferences. Two different groups of infants were tested, each presented with a pair of stimuli that were equated for one of the two properties and differed for the presence versus absence of the other property. For Group 1, both stimuli within the pair preserved a congruent relation

7 A Nonspecific Property Contributing to Newborns Face Preference 813 between the inner elements and the outer frame, and only one of the stimuli displayed the facelike arrangement of the inner elements that defines facedness. For Group 2, both stimuli displayed the facedness property, and only one of the two displayed a congruent relation between the inner elements and the outer frame (Figure 2). Based on the evidence provided by Experiment 2, we hypothesized that the attentional biases toward the two stimulus properties of facedness and congruency may exert a cumulative influence on newborns visual preferences, according to an additive model. Based on this hypothesis, we predicted that both groups of infants would prefer the stimulus in which both properties were present over the stimulus in which only one of the two properties was present. The alternative hypothesis, according to which the facelike disposition of the three inner elements that produces facedness, per se, is sufficient to trigger newborns attention toward faces (Johnson & Morton, 1991), would predict that no preference should be found for Group 2, whereas a preference for the facelike congruent stimulus should be found for Group 1. Method Participants. The final sample consisted of 33 (14 males) healthy, full-term infants, hr old, randomly assigned to two groups (16 in Group 1 and 17 in Group 2). Participants were middle-class infants, and 92% of them were Caucasian, 1% African, and 7% Asian. Ten additional infants were tested but not included in the sample due to position bias (n 5 1) or experimenter error (n 5 1), or because they did not complete testing due to fussiness (n 5 8). Stimuli. Two different pairs of stimuli of the same type as those used in Experiments 1 and 2 were employed, one for each group of participants. Each pair comprised a congruent facelike stimulus in which both the stimulus properties of facedness and congruency were present, and a stimulus similar to the previous one in which the facedness property (Group 1) or the congruency property (Group 2) was selectively removed. Therefore, in the first pair of stimuli (Group 1), the congruent facelike stimulus was contrasted with a congruent nonfacelike stimulus, whereas in the second pair (Group 2), the congruent facelike stimulus was contrasted with a noncongruent facelike stimulus (Figure 2). As in Experiments 1 and 2, the facelike versus nonfacelike appearance of the stimuli was produced by a 0 versus 180 rotation of the triplet of inner elements, and the congruent versus noncongruent nature of the stimuli was a product of the rotation of the triangular-shaped white area in which the elements were comprised. Apparatus and procedure. The apparatus and procedure were the same as those used in Experiment 1. Results Preliminary ANOVAs showed a significant main effect of the within-subjects factor of trial (first or second) for total fixation times, F(1, 31) , p 5.003, due to newborns producing longer fixation times in the first trial compared to the second trial. However, no significant interactions involving the factor of trial were found for either dependent variable. Therefore, two ANOVAs with group (Groups 1 and 2) as a between-subjects factor and stimulus properties (two properties and one property) as a within-subjects factor were performed, one for number of orienting responses and the other for total fixation time. No significant effects emerged for number of orienting responses. Newborns in Group 1 looked 13.1 (SD 5 4.4) times at the congruent facelike stimulus and 11.8 (SD 5 5.0) times at the congruent nonfacelike stimulus, t(15) , p 5.401, and newborns in Group 2 looked 11.7 (SD 5 6.2) times at the congruent facelike stimulus and 10.4 (SD 5 4.4) times at the noncongruent facelike stimulus, t(16) , p For total fixation time, there was a main effect of stimulus properties, F(1, 31) , p 5.003, due to fixation times to the congruent facelike stimulus being longer than fixation times to the second stimulus of the pair for each group. For Group 1, fixation times were 18% longer for the congruent facelike stimulus (M s, SD ) than for the congruent nonfacelike stimulus (M s, SD ), t(15) , p For Group 2, the facelike congruent stimulus was fixated 11% longer (M s, SD ) than the facelike noncongruent stimulus (M s, SD ), t(16) , p (all tests were two-tailed; Figure 2). Examination of the data for individual infants revealed that for Group 1, the number of infants who produced a greater number of looks at the congruent facelike stimulus did not differ from the number of infants who oriented more frequently toward the congruent nonfacelike stimulus (8 vs. 7, binomial test p and Wilcoxon test p 5.348), with one infant not included in the count because he or she made the same number of looks to the two stimuli. The number of infants who looked longer at one or the other stimulus was only marginally significant (11 vs. 5, binomial test p and Wilcoxon test p 5.063). For Group 2, 10 of 17 infants oriented more frequently toward the congruent facelike stimulus compared to

8 814 Macchi Cassia, Valenza, Simion, and Leo the noncongruent facelike stimulus (10 vs. 7, binomial test p and Wilcoxon test p 5.651), and 12 of 17 looked longer at this same stimulus (12 vs. 5, binomial test p and Wilcoxon test p 5.035; Figure 2). For both groups, the differences in looking times for the two stimuli ranged from 3.8 to s. Discussion Results from Experiment 3 showed that newborns manifested a spontaneous visual preference for stimuli in which both the facedness and the congruency properties were present over stimuli that comprised only one of these two properties. Specifically, evidence from Group 1 showed that the strength of congruency in triggering newborns attention increased when this property was accompanied by facedness. Evidence from Group 2 showed that facedness per se was not sufficient to preferentially attract newborns attention and that the attention-triggering value of the facelike arrangement of the inner elements was enhanced when the elements maintained a congruent relation with the external frame. This finding does not support the hypothesis of the existence at birth of a Conspec-like mechanism, which would be automatically activated by stimuli displaying the unique geometry of the face, defined by the correct relative location of the internal features for the eyes and mouth (i.e., facedness; Johnson & Morton, 1991; Johnson, 2005). Rather, the present findings are in line with recent claims that a number of attentional biases toward nonspecific stimulus properties combine to produce the face preference and demonstrate that the congruency bias is one of those biases (Simion et al., 2001, 2003). Results from Experiment 3 demonstrate that the attentional biases toward facedness and congruency have an additive effect in driving newborns preferences. The finding that the congruent facelike stimulus was preferred over both the congruent nonfacelike (Group 1) and the noncongruent facelike (Group 2) stimuli provide further support to the interpretation of the null results of Experiment 2. In fact, the two stimulus properties of facedness and congruency were capable of triggering newborns attention to the same extent in the two groups, and their cumulative influence on newborns visual preferences followed an additive rule. This finding provides support for the argument that both attentional biases toward facedness and congruency are involved in the preferential responses that newborns manifest for schematic faces. One final note of caution concerns the evidence emerging from Group 2, showing that facedness did not exert an all-or-nothing influence on newborns attention. This evidence derives from the comparison between two facelike stimuli, one displaying a congruent relation between the inner elements and the outer frame and the other in which the congruency property was not only missing but also intentionally violated by the misorientation of the outer frame. It is possible that the reduction of the figural goodness of the stimulus induced by this violation, rather than the cumulative effect produced by both the facedness and the congruency properties of the comparison stimulus, may have driven the preference for the congruent facelike stimulus observed in Group 2. If true, it could be hypothesized that if the congruent facelike stimulus was compared to a facelike stimulus in which the congruency property was neutralized, rather than violated, the facedness property would trigger newborns attention to the same extent in both stimuli. This possibility was tested in Experiment 4. Experiment 4 Experiment 4 was aimed at testing whether the preference observed in Group 2 of Experiment 3 would still be obtained when the congruent facelike stimulus is compared to a facelike configuration in which the triplet of inner elements is surrounded by a nonoriented, squared-shaped contour (Figure 3). If the congruent facelike stimulus was preferred in Experiment 3 because it included the two preferred properties of facedness and congruency, this preference should be maintained in Experiment 4. If, in contrast, the preference for the facelike congruent stimulus in Experiment 3 was a by-product of the reduced perceptual appeal produced by the violation of the congruency property in the stimulus to which it was compared, no preference should be expected in the present experiment. Method Participants. The final sample consisted of 15 (9 males) healthy, full-term, Caucasian infants, hr old. Two additional infants were tested but not included in the sample due to position bias (n 5 1) or fussiness (n 5 1). Stimuli. The stimuli in this experiment were the facelike congruent configuration presented in Experiment 3 and a facelike neutral stimulus in which the three squared elements were comprised within a white rectangular-shaped area whose width (24.2 ) and height (26.6 ) werethesameas those of the triangular-shaped area surrounding

9 A Nonspecific Property Contributing to Newborns Face Preference 815 compare number of orienting responses and total fixation time to the two stimuli presented. No difference was found for number of orienting responses. Newborns looked 15.5 (SD 5 5.8) times at the facelike congruent stimulus and 14.1 (SD 5 6.6) times at the facelike neutral stimulus, t(14) , p In contrast, fixation times were 20% longer to the facelike congruent stimulus (M s, SD ) than to the facelike neutral stimulus (M s, SD ), t(14) , p (Figure 3). Examination of the data for individual infants showed that almost half of the infants in the sample oriented more frequently toward the facelike congruent stimulus (7 vs. 8, binomial test p and Wilcoxon test p 5.733), whereas two thirds of the infants looked longer at this same stimulus (11 vs. 4, binomial test p and Wilcoxon test p 5.061; Figure 3). The differences in looking times for the two stimuli ranged from 1.6 to 68.0 s. Figure 3. Stimulus pairs and results from Experiment 4. Note. The first graph shows the total fixation time toward each stimulus and the second shows the number of newborns who oriented more frequently and/or looked longer toward each stimulus. The p values refer to the comparison between the stimuli, and the error bars indicate standard deviations. *p,.05. the inner elements in the facelike congruent stimulus (Figure 3). Apparatus and procedure. The apparatus and procedure were the same as those used in Experiment 1. Results Preliminary ANOVAs showed a significant main effect of the within-subjects factor of trial (first or second) for total fixation times, F(1, 14) , p 5.007, due to fixation times being longer during the first trial compared to the second trial, but no significant interactions involving this factor were found for either dependent variable. Therefore, two separated t tests for dependent samples were performed to Discussion The results showed that the preference for the congruent facelike stimulus persevered when this stimulus was contrasted to a facelike stimulus in which the congruency property was neutralized by the presence of a nonoriented external contour. This finding demonstrates that the preference for the congruent facelike stimulus over the noncongruent facelike stimulus observed in Experiment 3 was truly due to the cumulative effect of the facedness and congruency properties. Moreover, this finding replicates and extends the results of Experiment 3, showing that the facedness property is capable of eliciting a preferential response only when the congruency property is concurrently present within the stimulus. By replicating the findings of Experiment 3, the results of Experiment 4 provided further evidence for the additive effect exerts by congruency and facedness on newborns visual preferences. The demonstration that the attentional biases toward these two stimulus properties produce a cumulative effect on newborns visual preferences according to an additive model is in agreement with the claim that newborns face preference derives from the cumulative action of a set of attentional biases toward different nonspecific stimulus properties that faces share with other nonface stimuli, rather than from one single specific bias toward facedness (Simion et al., 2001, 2003). However, this claim would receive much stronger support by the demonstration that the same cumulative effect on newborns preferences could be found with congruent stimuli in which facedness is

10 816 Macchi Cassia, Valenza, Simion, and Leo not confounded with top-heaviness. In fact, it is important to highlight that the nonspecific structural property of top-heaviness was inherently embedded in the facelike stimuli used in Experiments 3 and 4. Therefore, top-heaviness may have played a critical role in triggering newborns preferences toward these stimuli. Using top-heavy stimuli displaying a nonfacelike disposition of the inner elements, in Experiment 5, we tested the hypothesis that the two perceptual properties of congruency and topheaviness produce a cumulative effect on newborns preferences. Experiment 5 Experiment 5 was aimed at extending the results obtained for Group 2 of Experiment 3 to top-heavy stimuli that do not display the facelike arrangement of the inner elements, which defines facedness. Specifically, the goal was to provide direct evidence concerning the additive effect of the top-heavy bias and the congruency bias in driving newborns preferences. Newborns were presented with a pair of compound stimuli comprising five elements, which were arranged so as to create a top-heavy nonfacelike configuration. Specifically, the elements were more numerous in the upper part compared to the lower part but not disposed in correct location for the eyes and mouth, as it was in the schematic facelike stimuli used in Experiments 2 through 4. Although being equated for the top-heavy configuration of the elements, the two stimuli differed for the orientation of the white area surrounding them, which was congruent with the spatial arrangement of the elements in one stimulus and incongruent with those elements in the second stimulus (Figure 4). Method Participants. The final sample consisted of 12 (7 males) healthy, full-term newborn infants, hr old. Participants were middle-class infants, and 98% of them were Caucasian and 2% Asian. Two additional infants were tested but not included in the sample due to fussiness. Stimuli. Each stimulus comprised four black square elements of the same size as those composing the stimuli used in Experiments 1 through 4 and one rectangular-shaped element that was 2.2 cm (4.2 ) high and 5.9 (11.2 ) wide. The distance between the elements was 1 cm (1.9 ). Three of the four squared elements were located in the upper part of the stimulus, and only one was located in the lower part, Figure 4. Stimulus pairs and results from Experiment 5. Note. The first graph shows the total fixation time toward each stimulus and the second shows the number of newborns who oriented more frequently and/or looked longer toward each stimulus. The p values refer to the comparison between the stimuli, and the error bars indicate standard deviations. *p,.05. ***p,.001. with the rectangular-shaped element located in the middle, so as to create a top-heavy configuration. The elements were located into a white area, which differed in shape but not in size from that used in Experiments 1 through 4. The orientation of the white area paralleled the top-heavy distribution of the elements in the congruent stimulus and rotated 180 on the noncongruent stimulus (Figure 4). Apparatus and procedure. The apparatus and procedure were the same as those used in Experiment 1.

11 A Nonspecific Property Contributing to Newborns Face Preference 817 Results Preliminary ANOVAs showed no significant main effects or interactions involving the within-subjects factor of trial (first or second) for either dependent variable. Therefore, two paired-sample t tests were performed to determine whether newborns number of orienting responses and total fixation time differed for the two stimuli presented. Newborns showed a marginally significant trend to orient more frequently to the top-heavy congruent stimulus (M , SD 5 3.1) rather than the top-heavy noncongruent stimulus (M 5 8.2, SD 5 3.5), t(11) , p This trend reached statistical significance for total fixation times, which were 29% longer to the topheavy congruent stimulus (M s, SD ) than to the noncongruent stimulus (M s, SD 5 9.8), t(11) , p,.001 (both tests were two-tailed; Figure 4). Examination of the data for individual infants showed that only two thirds of the infants in the sample oriented more frequently toward the topheavy congruent stimulus (8 vs. 3, binomial test p and Wilcoxon test p 5.107), with one infant not included in the count because he or she made the same number of looks to the two stimuli, and almost all the infants looked longer at the same stimulus (11 vs. 1, binomial test p and Wilcoxon test p 5.004; Figure 4). The differences in looking times for the two stimuli ranged from 4.9 to 40.5 s. Discussion The results showed that the top-heavy congruent stimulus was preferred over the top-heavy noncongruent stimulus, thus indicating that the congruency and top-heavy properties have an additive effect on newborns preferences. When compared to the results obtained for Group 2 of Experiment 3, the findings from the present experiment suggest that the presence of the congruency property is crucial in determining the preference for top-heavy configurations in the same way as it is crucial for the emergence of the preference for schematic facelike configurations. General Discussion The results of the present study extend our knowledge concerning the stimulus properties capable of eliciting spontaneous visual preferences at birth (see Slater, 1995, for a review). Evidence from Experiment 1 shows that when two stimuli for which no preference has been shown to exist at birth are equated for the quantity of energy they contain (i.e., number of elements, contrast information), a configural property emerging from the spatial relations among the stimulus components (Kimchi, 1992) can induce a visual preference in newborns. This finding adds to other evidence showing that newborns manifest a preference for stimuli displaying specific distributions of energy within the pattern (i.e., specific structural properties), such as that for horizontal over vertical configurations (Farroni et al., 2000; Slater & Sykes, 1977; Slater et al., 1985) and for top-heavy patterns over bottom-heavy patterns (Simion et al., 2002). Together, these findings demonstrate that newborns are sensitive to stimulus dimensions other than those specified by physical, low-level properties (i.e., contrast information, spatial frequencies; Banks & Ginsburg, 1985; Banks & Salapatek, 1981). Crucially, these findings are the first to demonstrate that newborns are sensitive to a configural, relational property generated by the interdependency among different features of the stimulus the shape/ orientation of the outer frame and the spatial relation among the inner features. In fact, to prefer the congruent pattern over noncongruent pattern in Experiment 1, and in the other experiments, newborns must not only organize the three squared blobs in a triangular configuration but also perceive the relationship between the triangular configuration of the internal elements and the orientation of the external frame. Therefore, overall the present findings demonstrate that newborns are sensitive to the relation between inner and outer features of the stimulus and appreciate the redundancy and regularity of this relation, independently of the facelike or nonfacelike appearance of the stimulus. Notably, with regard to faces, the presence since birth of the basic ability to extract the perceptual attributes of the relation between the inner and the outer features of the stimulus does not prevent infants from treating these features as independent cues for individual face recognition until around 7 months of age, when holistic processing of internal and external facial features has been found to first emerge (Cashon & Cohen, 2004; Schwarzer, Zauner, & Jovanovic, 2007). Just as for preferences based on the physical properties of stimuli (Banks & Ginsburg, 1985; Banks & Salapatek, 1981), stimulus preferences based on the energy distribution within the pattern have been interpreted as resulting from constraints on the newborns visual system, which would render some stimuli more easily detectable and explored than others. For example, newborns preference for horizontal configurations over vertical configurations has been attributed to eye movements, which at birth tend