Face processing in high-functioning adolescents with autism: Evidence for weak central coherence

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1 VISUAL COGNITION, 2004, 11 6), 673±688 Face processing in high-functioning adolescents with autism: Evidence for weak central coherence Beatriz LoÂpez School of Sports Science and Psychology, York St John College, UK Nick Donnelly Centre for Visual Cognition, University of Southampton, UK Julie A. Hadwin Centre for Research into Psychological Development, Department of Psychology, University of Southampton, UK Susan R. Leekam Department of Psychology, University of Durham, UK Seventeen adolescents with autism and seventeen typically developingchildren, matched for chronological age, were tested in a whole versus part paradigm in which participants matched a face target either to a complete face or to a face feature. Previous studies showed an accuracy advantage in whole-face matching, indicatinga holistic processingadvantage for adults Donnelly & Davidoff, 1999). It has been suggested that individuals with autism have difficulty in holistic processing, however the extent to which this difficulty may be moderated by attentional cues is uncertain. The present study included a condition that cued participants to the relevant face feature for matching. In the comparison group, the cue did not moderate the whole-face matchingadvantage. In the participants with autism, cueing generated a whole-face advantage, while uncued stimuli showed no difference between whole face and feature matching. This suggests that a lack of holistic processingin face processing, which is associated with individuals with autism, can be moderated with cueing. The implications for weak central coherence theory are discussed. Please address all correspondence to School of Sports Science and Psychology, York St John College, Lord Mayor's Walk, York YO31 7EX, UK. B.Lopez@yorksj.ac.uk This research was funded by a doctoral research grant to the first author from the Department of Psychology of the University of Kent at Canterbury. During the period of the research all authors were members of the University of Kent. We would like to thank the parents, children, and the staff from the followingschools for their kind cooperation: Axton Chase, The Abbey School, Helen Allison, and Sandwich and Hartsdown Technology Schools. Finally, the authors would like to thank the anonymous reviewers for their feedback. # 2004 Psychology Press Ltd DOI: /

2 674 LOÂ PEZ ET AL. Central coherence is defined as a tendency to integrate information into meaningful representations Frith, 1989). It has been proposed that autism is characterized by weak central coherence, which manifests in a bias towards attendingto the local features of objects Ropar & Mitchell, 2001; Shah & Frith, 1983, 1993), and a relative impairment in global perception Mottron & Belleville, 1993). With respect to evidence for a local bias, superior perception of object parts in individuals with autism, relative to control participants, has been demonstrated in a number of different tasks such as the Embedded Figure test Jolliffe & Baron-Cohen, 1997; Shah & Frith, 1983) or the Block Design test Shah & Frith, 1993). Evidence for the relative impairment in global perception in autism has been largely drawn from performance on the Navon task Navon, 1977). In the traditional Navon task, participants are shown larger letters made up from smaller letters, where these have the same or a different identity to the large letter. When typically developingchildren or adults are asked to report the identity of the large letter, the identity of the small letter interferes, leading to a slowingof reaction times and increased number of errors i.e., ``interference effect''). In contrast, when reportingthe identity of the large letter, there is no interference from the small letters. This effect is referred to as the ``global precedence effect''. The predictions from central coherence theory in relation to the Navon task are that, as a result of a global impairment, individuals with autism would have local interference and local advantage effects in this task. Studies investigating the performance of individuals with autism in this task have, however, provided mixed results. Whilst one study found a local interference effect, but neither local nor global advantage Mottron & Belleville, 1993; Plaisted, Swettenham, & Rees, 1999, Exp. 1), three other studies have failed to find evidence for either local advantage or local interference Mottron, Burack, Stauder, & Robaey, 1999; Ozonoff, Strayer, McMahon, & Filloux, 1994; Plaisted et al., 1999, Exp. 2). However, there is reason to believe that the Navon task is not a reliable procedure to test global and local processing. Lamb and Robertson 1989) have found evidence to show that changes in factors such as discriminability, density, size, or brightness can reduce or even reverse the global advantage and interference effects. One study usingthe Navon task has, however, has provided some insight into global processing abilities in autism Plaisted et al., 1999). In this study, they compared performance of the same individuals with autism in two versions of the Navon task in which almost identical stimuli were presented and only the procedure changed. In one version participants were cued to either the local or global level, whilst in the other version no cues were given. Results showed that individuals with autism only exhibited global processing when cues were provided. Given that the stimuli in the two versions were practically the same, it can

3 HOLISTIC FACE PROCESSING IN AUTISM 675 be concluded that cueingindividuals with autism to either the local or global level enhances global processing abilities that otherwise are impaired. An additional source of evidence of global processing abilities comes from studies using face recognition tasks. Face processing, unlike other types of visual processing, involves both configural and feature information. Two types of configural processing have been identifiedðholistic processing and secondorder relational processing Maurer, LeGrand, & Mondloch, 2002). In the present paper, we investigate holistic processing as defined by the formation of faces as undifferentiated wholes, such that wholes cannot easily be broken down into separate features e.g., Davidoff & Donnelly, 1990; Tanaka & Farah, 1993). With respect to development, holistic processing, has been found in typically developingchildren as youngas 6 years of age Carey & Diamond, 1994; Tanaka, Kay, Grinnell, Stansfield & Szechter, 1998). In these studies, children were asked to recognize either the top half of a composite face, relative to fullface and half-face baselines Carey & Diamond, 1994), or to match a target face to either complete faces or part faces Tanaka et al., 1998). Six-year-old children showed interference in the composite face task and matched complete faces better than part faces, demonstratingholistic face processing. In addition, Carey and Diamond have demonstrated increased interference in holistic processing with age when faces are inverted, a finding that suggests development from feature-based to holistic face processing. Previous research has investigated configural face processing in autism although only one study has investigated holistic processing specifically Joseph & Tanaka, 2003). For example, Hobson, Ouston, and Lee 1988) and Langdell 1978) investigated the effect of face inversion on face recognition in this population and found that children with autism are less affected by inversion, compared to typically developingchildren. Because of this lack of interference in face processingwhen faces are inverted, these data have been used to argue that children with autism rely on feature processingfor face recognition. Other studies have, however, failed to find this superiority for inverted over upright faces Tantam, Monagham, Nicholson, & Sterling, 1989; Teunisse, 1996, Exp. 1), questioning the reliability and generality of this finding. The relative abilities of individuals with autism compared with other groups across a range of face matching tasks have also been measured Davies, Bishop, Manstead, & Tantam, 1994). Davies et al. demonstrated that high functioning individuals with autism were poorer at matchingfacial expressions, identity, and emotion. In this study children with autism also had difficulty with a nonfacial task to test for holistic processing of patterns, which suggests that impairments in autism are not restricted to the processingof facial stimuli. These studies have provided indirect evidence of some form of deficit in configural processing of faces in autism, although whether this is in the processing of holistic features, second-order relational features, or both is unclear. More recently, studies have

4 676 LOÂ PEZ ET AL. reported atypical weak activation of the ``fusiform gyrus'', an area believed to be responsible for the processingof facial stimuli Critchley, Daly, Bullmore, Williams, van Amelsvoort, Robertson, et al., 2000; Schultz, Gauthier, Klin, Fulbright, Anderson, Volkmar, et al., 2000). A common assumption held by researchers within the weak central coherence account is that the presence of a local bias in autism is due to a failure to process global patterns of stimuli HappeÂ, 1999, 2001). Superior featural processingdoes not however necessarily entail a lack of global processing abilities. It is therefore important when investigating weak central coherence in autism to confirm the existence of a global impairment by directly assessing global processing abilities. In the present study, we report one experiment used previously with adult brain-damaged patients Donnelly & Davidoff, 1999). In this experiment participants are presented with a picture of a target face followed by two probes. In some trials, probes consist of two complete faces differingonly by one feature. Alternatively, trials consist of two isolated features i.e., two noses, two eyes, or two mouths). In the complete face trials, participants have to decide which of the two faces matches the target face. In the feature trials, participants have to decide which of the two features was presented in the target face. Results from previous research have shown that, typically, adults perform better in the complete face condition compared with the feature condition, an effect known as the complete probe advantage CPA; see, e.g., Donnelly & Davidoff, 1999). This paradigm allows a direct test of the presence or absence of holistic face processingas it measures the extent to which participants make use of holistic information of faces to identify features. The whole versus part paradigm has been used previously in an investigation of face processingin children with autism Joseph & Tanaka, 2003). Children with autism demonstrated CPA but only when comparisons involved the mouth feature. In contrast, typically developingchildren between the ages of 9 and 11 showed an advantage for recognizing whole over part faces when comparisons were made across eye and mouth features. One goal of the present study is to examine whether the same effect of feature type can be replicated with a different sample. A manipulation of the whole versus part task also allows an exploration into the effect of cues in face processing. Donnelly and Davidoff 1999, Exp. 5) showed that by presentinga cue immediately before the target face to inform participants of the feature on which to base their matchingdecision i.e., ``Look at the nose'') facilitated, but did not qualitatively change, performance in both complete face and feature trials Donnelly & Davidoff, 1999). In contrast, in autism typical holistic processingseems to emerge only in the presence of cues Plaisted et al., 1999). In order to investigate the impact of cueing on face processingin autism the present study consisted of two conditions. In the first condition, a cue was presented immediately before the target face to inform participants of the feature on which to base their matchingdecision. In the

5 uncued task, no cue was provided. If individuals with autism have weak central coherence, they would fail to show a CPA under cued or uncued conditions. In contrast, a CPA obtained under cued conditions would support the idea that central coherence can be modulated by attentional instruction Plaisted et al., 1999). The cueingmanipulation within the whole±part task is also of interest given the results of Joseph and Tanaka 2003). If the effect of findinga difference between whole and part probes for mouths, but not for other features, can be replicated in the uncued task, the role that cueingmight have in alteringthis unusual face encoding strategy might be informative. In particular, comparing results found with different features and probe types across cued and uncued tasks might help in understanding whether face processing strategies employed in autism are open to modification by changing task demands. METHOD Participants Seventeen high functioning adolescents with autistic disorder AD) took part in the study. The children were recruited from a range of special schools in Kent, UK. All had received a diagnosis of autism by experienced clinicians using the guidelines of standard criteria as DSM±IV APA, 1994), DSM±III±R APA, 1987), or ICD-10 WHO, 1990). Participants' IQs were measured usingfour subtests of the Weschler Intelligence Scale for ChildrenÐRevised WISC±R; Weschler, 1974; Information, Vocabulary, Block Design, and Object Assembly). These four subtests were chosen followingozonoff et al. 1994), because they load most highly on the verbal comprehension and perceptual organization factors of the WISC±III Weschler, 1974). The control group consisted of a group of 17 typically developing children TD) approximately matched on chronological age to the autism group. These children were recruited from range of local schools in Kent, UK. The groups did not significantly differ in chronological age CA), t 32) = 0.997, p >.05, verbal IQ VIQ), t 32) = 0.865, p >.05, performance IQ PIQ), t 32) = 1.807, p >.05, nor full-scale IQ FIQ), t 32) = 1.382, p >.05. Table 1 summarizes participant characteristics for both groups of children. Stimuli HOLISTIC FACE PROCESSING IN AUTISM 677 The same stimuli as in Donnelly and Davidoff 1999) were used in the present study. There were two probe typesðcomplete faces and features. For the complete face probes a set of six target faces was formed in which the features of eyes, nose, and mouth were varied, keepingall other aspects of the face constant. The feature probes comprised three examples of eyes, noses, and mouths.

6 678 LOÂ PEZ ET AL. TABLE 1 Chronological age CA), verbal IQ* VIQ), performance IQ* PIQ) and full scale IQ* FIQ) mean scores of adolescents with autism AD) and typically developing children TD), with standard deviation in parentheses Group CA VIQ PIQ FIQ TD N = 17) ) ) ) ) AD N = 17) ) ) ) ) * Verbal, performance and full scale mean scores as measured with Weschler Intelligence Scale for ChildrenÐRevised WISC±R; Weschler, 1974). In complete face trials, the target was presented alongside a second face that was identical except for the replacement of one feature. No distractor face was the same as any other target face. In feature trials, a feature eye, nose, or mouth) presented previously in the target face was presented alongside an alternative feature eye, nose, or mouth, respectively). Targets were presented to either the left or right of distractors. There were 36 complete face and 36 feature trials. Examples of complete and feature trials are shown in Figure 1. COMPLETE CONDITION FEATURE CONDITION Figure 1. Examples of stimuli used in the complete face and feature conditions.

7 Apparatus The stimuli and the cues were presented in a Macintosh Laptop computer using Superlab software. Design A mixed design was employed. The within-participants factors were probe type complete face vs. feature), feature type eyes vs. noses vs. mouths) and cueing condition uncued vs. cued). The between-participants factor was group children with autism vs. typically developingchildren). The dependent measure was the number of correct responses. Procedure HOLISTIC FACE PROCESSING IN AUTISM 679 Children were taken individually to work in a quiet room. Participants were presented with a complete face on the screen. After a short delay 500 ms) two items were presented. Participants had to decide which item matched the face they had previously seen by pressingone of two keys in the keyboardð''a'' for the item on the left, or ``l'' for the item on the right. In complete trials, the two items were two complete faces, one of which matched the previous face. In feature trials, the two items were two features i.e., two pairs of eyes, two noses, or two mouths) and the participants had to decide which of them belonged to the face presented before. In the complete trials, the target face and the distractor differed only in one feature. All participants were presented with the cued condition first. In the cued condition, a cue was presented immediately before the target face to inform participants of the feature on which to base their matchingdecision i.e., ``Look at the mouth''). The presentation time of cues was 1000 ms and the exposure time of the target face was 500 ms. There was a 500 ms interstimulus interval between cue and target presentation. The uncued condition was administered after completion of the cued condition and the procedure followed was exactly the same, except that no cues were provided prior to the presentation of targets. RESULTS One sample t-test confirmed that responses were above chance level for all across groups. The mean accuracy scores for each condition are presented in Table 2 for both TD and AD groups. CA and FIQ scores were not significantly different in the two groups, however, as individual matchinghad not been used and, as previous research shows that holistic processingseems to be related to CA e.g., Carey & Diamond, 1994), these variables were included as covariates in the analysis of the data.

8 TABLE 2 Mean accuracy scores % in brackets) and standard error for cued and uncued conditions maximum = 12) Cued Uncued Complete Part Complete Part Group Eye Nose Mouth Eye Nose Mouth Eye Nose Mouth Eye Nose Mouth TD N = 17) Mean ) ) ) ) ) ) ) ) ) ) ) ) SE AD N = 17) Mean ) ) ) ) ) ) ) ) ) ) ) ) SE

9 HOLISTIC FACE PROCESSING IN AUTISM 681 A four-way mixed repeated measures ANCOVA was run with probe type complete probe vs. feature), feature type eye vs. nose vs. mouth) and cue cued vs. uncued) as within-participants factors, group AD vs. TD) as a betweenparticipants factor and CA and FIQ as covariates. Results showed a significant interaction of CA and probe type, F 1, 30) = 5.152, p <.05, suggesting that CA moderates the CPA. CA however did not have a significant effect in overall performance, F 1, 30) = 0.021, p >.05. FIQ was significantly related to overall accuracy scores, F 1, 30) = 9.635, p <.01, and interacted significantly with cue, F 1, 30) = 5.026, p <.05, indicatingthat the ability to use cues effectively depends on the IQ level. The analysis revealed a significant main effect of probe type, F 1, 30) = 4.650, p <.05, indicatingthat children were more accurate when recognizing complete faces rather than isolated features. A significant interaction was found between cue and group, F 1, 37) = 4.203, p <.05, indicatingthat cues enhanced performance significantly more in TD children compared with AD children. Neither the main effects of feature, cues, or group yielded significance, F 2, 60) < 1; F 1, 30) = 0.592, p >.05; F 1, 30) = 2.588, p >.05, respectively. The interaction between cue and probe type was not significant either, F 1, 37) = 0.405, p >.05. No interaction involvingthe feature factor approached significance all F ratios < 2.2). Finally, there was a significant three-way interaction between cue, probe type, and group, F 1, 30) = 5.408, p <.05. To further investigate the source of the three-way interaction, two-way ANOVAs were run for each group separately with cue cued vs. uncued) and probe type complete face vs. feature) as withinparticipants factors. The covariates were not included in this analysis because none of them interacted significantly with group. The Cue 6 Probe type 6 Group interaction is explained by a significant interaction of probe type and cue in the AD sample, F 1, 16) = , p <.01, but not in the TD group, F 1, 16) = 0.004, p >.05. Post hoc tests to explore the source of this interaction revealed that only when given a cue were children with autism more accurate in the complete face condition, t 16) = 4.722, p <.01. In the uncued condition, AD children showed no difference between the complete face and the feature conditions, t 16) = 0.260, p >.05. TD children on the other hand were more accurate in the complete face compared with the feature condition for both the cued and uncued conditions, t 16) = 2.680, p <.05; t 16) = 2.582, p <.05, respectively. DISCUSSION The results of the cued condition demonstrated that both groups showed a CPA, that is, better performance on the complete face than in the part face condition. This findingprovides clear evidence that individuals with autism are able to recognize faces using holistic information under certain conditions. These

10 682 LOÂ PEZ ET AL. results, therefore, run contrary to some previous findings suggesting an across the board deficit in holistic processing e.g., Mottron & Belleville, 1993). In contrast, the results support other findings that provide evidence for the presence of holistic processingunder appropriate testingconditions Ozonoff et al., 1994). In addition, the results showed that the AD group did not perform more accurately compared with the TD group in the part face condition, a result that does not confirm the presence of superior feature processingin this group. One conclusion from this study could be therefore, that the results do not support the proposition of weak central coherence in autism. An alternative interpretation of these results is, however, that the use of cues is critical in accountingfor the pattern of results found in the AD and TD groups. The analysis comparingperformance in the cued and uncued conditions revealed one important finding. Only TD children, and not children with autism, showed evidence of CPA in both conditions. Research usingcues to manipulate attention in the Navon task has shown that they can enhance holistic processingin individuals with autism Plaisted et al., 1999). Likewise, in the present experiment performance in the autism group was similar to that of TD group when attention was manipulated by use of cues, whilst in the absence of cues the AD group failed to present the typical CPA, a finding suggesting that holistic processingseems to be intact in autism but operates only under certain conditions. One explanation Plaisted et al. 1999) propose for the atypical pattern of performance present in autism in the absence of cues is that in autism there are abnormal high levels of activity in the channels responsible for local information processingwhich can be suppressed by overtly instructingparticipants to focus on the global level. This explanation, however, cannot account for the present findings, as the cues used in this study did not instruct participants to focus on the global level but on the features. It would therefore be reasonable to expect more activation of the channels responsible to process the local features, and thus enhanced performance in feature probe trials, especially if we consider the evidence showingthat focusingattention to one level enhances performance in that level Kinchla, Solis-Macias, & Hoffman, 1983). In contrast, in this experiment, cues informingabout the relevant feature enhanced performance on both feature and complete probe trials in the typical sample, a pattern consistent with adult's performance in Donnelly and Davidoff 1999), and only complete trials in the autism sample. The pattern found in the TD sample resembles the findings with adults in Donnelly and Davidoff who also found that feature cues also enhanced complete and part probe trials in adults relative to either not providingcues or providingcues about the type of trial that followed complete or part probe. The explanation provided by Donnelly and Davidoff for this counterintuitive effect is that faces are processed in an automatic, mandatory fashion that cannot be override by the provision of cues. Cues only serve to inform this automatic processingand hence the enhanced performance for both whole and part trials.

11 HOLISTIC FACE PROCESSING IN AUTISM 683 Joseph and Tanaka 2003) found CPA only for mouths but not for eyes, a result that is consistent with studies showingimpaired use of eye gaze in autism across a wide range of tasks e.g., Joseph & Tager-Flusberg, 1997; Baron- Cohen, Baldwin, & Crowson, 1997). They argue that establishing whether cues enhance holistic processingin individuals with autism may help to determine if holistic face processing is mandatory, as suggested by Donnelly and Davidoff 1999), or a result of cumulative experience as suggested by Carey and Diamond 1994). If despite their reduced experience for eyes, individuals with autism present CPA across the different feature trials i.e., eyes, nose, and mouths) under cued conditions, it can be concluded that holistic face processingis a mandatory process independent of experience. In this study we have found that under cued conditions children with autism exhibit holistic processingacross feature trials, a finding that suggests that holistic face processing is indeed a mandatory process. It is important to note that Joseph and Tanaka 2003) have previously reported a CPA for comparisons involvingmouths but not eyes. The data from the uncued condition of the present study, however, did not show any evidence of mouths havinga special status in the autistic population. In these terms, the data do not replicate those of Joseph and Tanaka. Nevertheless, the population of children with autism were different in the two studies and the tasks used in the studies also differed. First, the population of children tested in the present study were around 3 years older than those tested by Joseph and Tanaka. It is possible, therefore, that effects present at one age are different to those present at another. Second, Joseph and Tanaka used photographic images, whereas line drawings were used in the present study. Although both types of stimulus are known to evoke face specific processing, as measured by the fact that they generate face specific evoked potentials Jeffreys, 1996), Donnelly and Hadwin 2003) have reported that it is easier to find evidence for configural processing when using greyscale photographic images than monochrome images. In their task, even children as youngas 6 years' old could detect the Thatcher illusion effortlessly with greyscale images, but were not above chance for matched monochrome images. In other words, the present task might have been harder than that of Joseph and Tanaka because of the images used and overall accuracy rates in the two experiments support this conclusion 69% vs. 61% for Joseph and Tanaka and the uncued condition of the present experiment, respectively). Consequently, the Joseph and Tanaka stimuli might have been better suited to revealingsubtle whole-part effects than those used in the present study. Although the Joseph and Tanaka findings remain to be replicated, the present data should not necessarily be interpreted as a failure to replicate their finding. If holistic processingof faces is a mandatory process, as the results from the cued task suggest, the remaining question is why individuals with autism fail to present CPA in uncued conditions. As argued earlier, the explanation cannot be related to enhanced activation in the channels responsible for local information

12 684 LOÂ PEZ ET AL. processing. The other alternative proposed by Plaisted et al. 1999) for the cue effect is that individuals with autism have difficulty shiftingfrom the local to the global level and vice versa. There is numerous evidence of attention shifting difficulties in autism e.g., Casey, Gordon, Mannheim, & Rumsey, 1993; Courchesne et al., 1994). Plaisted et al. argue that individuals with autism might have difficulty with the divided attention version of the Navon task because participants have to shift continuously from one level to the other. Attention shiftingdifficulties seem to be an unlikely explanation for the pattern of results in the present experiment for two reasons. First, there is evidence that individuals with autism do not have difficulty with continuous attention shifting Pascualvaca, Fantie, Papageorgiou & Mirsky, 1998), that is, in tasks that require successive comparisons between stimuli, as did the task employed in the present study. Second, as Plaisted et al. argue, attention shifting difficulties could not explain entirely the results as attention shiftingdifficulties would not produce any advantage or interference effects in the Navon task, similarly in this task no CPA should have been found in either condition. All in all, it seems the most likely explanation for the pattern of results found in this study is that, as Plaisted et al. suggest, central coherence is intact in autism but needs overt priming. In this case, children with autism seem to need the extra information provided by cues. The better overall performance in the cued, relative to the uncued task, in the TD group for complete and part face conditions was not significantly different from that found for the AD group in the complete face condition as shown by the nonsignificant interaction between cue and group. This result indicates that the effect of cueingwas, at least in the complete face condition, equivalent for both AD and TD groups. In other words, the similarity of improvement in performance in the complete face conditions in the cued task for AD and TD groups means that cues must have been attended to equally by both groups. Given that the cues presented in the cued task were attended to by the AD group to the same extent as the TD group, the question that needs to be addressed is why performance in the AD group was only enhanced in the complete face condition and not in the feature condition. There is wide evidence that providingnonspecific cues enhances performance in other types of behaviours that otherwise are impaired, such as gaze following Leekam, Hunnisett, & Moore, 1998) or symbolic play Gould, 1986; Lewis & Boucher, 1995). It might be possible that in this task cues also enhanced performance by merely alertingtheir attention in a nonspecific way but, whilst this is a possibility, it would not explain why performance did not increase for feature trials. It has been shown that individuals with autism have difficulties usinginformation about cues effectively to generate expectations about the location of a target Wainwright-Sharp & Bryson, 1993). Thus cues could activate mandatory holistic face processing increasingperformance in complete trials but at the same time the inability to effectively use the information of cues would prevent enhanced performance for

13 HOLISTIC FACE PROCESSING IN AUTISM 685 features in the cued condition. Research should further investigate the ability to use information provided by cues in autism. The children with autism in this study did not preferentially attend to features in the uncued condition, as shown by the accuracy scores which were similar to those of the TD sample. This failure to find evidence of superior feature processingin either the cued or uncued conditions in the autism group confirms the findings by other authors. Who failed to find evidence of a local bias in face processing Teunisse, 1996, Exp. 2), detectingembedded figures Brian & Bryson, 1996; Jolliffe & Baron-Cohen, 1997) and reported typical sensitivity to visual illusions Ropar & Mitchell, 1999). It would be reasonable to conclude therefore that there is not enough evidence to support the claim that autism is characterized by a local bias. The contradictory results from the different studies regarding the presence of a local bias in autism may be however explained by differences in the populations studied and in the tasks used. A common criticism to the study of Brian and Bryson is that they included participants with pervasive developmental disorders who might not have the same type of impairments as children with autism. Jolliffe and Baron-Cohen used a sample of high-functioningchildren with autism, which might explain why they found differences in reaction times only as accuracy levels were very high for both samples. Finally, in relation to the contradictory findings in visual illusions tasks, a recent study by Ropar and Mitchell 2001) has shown that performance on visual illusions is not related to performance on other visuospatial tasks, such as the Block Design or the Embedded Figures tests. Only those studies using face stimuli i.e., Teunisse, Exp. 2, and the present study) fail to provide support for the presence of a local bias in autism. There is evidence of a general face processing deficit in autism Boucher & Lewis, 1992; de Gelder, Vroomen, & van der Heide, 1991; Gepner, de Gelder, & Schonen, 1996). Thus, it is feasible that the failure to find enhanced performance for features is not related to the lack of a local bias in autism but to a difficulty in processing facial stimuli. The original findings of Shah and Frith 1983) therefore remain uncontested. A weakness of this study is that it did not have a control task with nonfacial stimuli. The CPA is not a phenomena restricted to facial stimuli. There is also CPA for objects, whereby parts of objects are better recognized when presented within the context of the complete object, a phenomena known as object superiority effect Weisstein & Harris, 1974). Evidence shows weakened activation of the fusyform gyrus in autism and stronger activation of the inferior temporal gyri responsible for object processing which would suggest that individuals with autism treat faces as objects Schultz et al., 2000). It would be interestingto see how performance in a face task testingfor face superiority, compared to the task testingfor object superiority effect used in this study. If the difficulty in autism is related to a general impairment as weak central coherence suggests, we would predict a similar pattern of results as found in the present study, that is, CPA only when cues were provided. If the difficulty in autism is

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