Face processing in Williams Syndrome and autism

Abstract

Individuals with Williams syndrome (WS) have been characterised as hyper-sociable, showing an extreme compulsion to engage in communication with other people, whilst the opposite has been cited regarding autism. The most important social cue in our environment is the human face, which must be successfully recognised and interpreted for communicative signals. Although clear differences are apparent in social skills, individuals with WS and autism have been described as showing similarly atypical face processing styles. The present research addressed issues of face perception in Williams syndrome and autism to gain further insights into social abilities of individuals with these developmental disorders. Importantly, the research was grounded in typical face perception methods. The investigation began with a large-scale exploration of face skills, probing identity, eye gaze, expressions of emotion and lip reading to ask how these two disorders uniquely impact upon performance. Participants with WS and autism could be dissociated from those with general developmental delay and from each other primarily on the basis of eye gaze ability. Participants with WS showed strong eye gaze abilities whilst participants with autism had extreme difficulties. Although interpretation of expressions of emotion also showed a difference between groups, autism and WS did not uniquely impact upon the processing of identity or lip reading. The exploration also allowed the consideration of models of face perception; characterised by a typical modular structure in WS but a lack of modularity in autism. The second line of inquiry considered identity processing and firstly asked whether participants were more accurate at matching faces from internal or external features. Participants with WS showed an atypical use of internal features for matching unfamiliar faces, which may be linked to an atypical interaction style and exaggerated interest in unfamiliar people. Participants with autism used the same strategy to match faces of familiar and unfamiliar people and hence familiarity did not impact upon processing style. Subsequent chapters probed feature salience (eyes .v. mouth) and structural encoding. Across paradigms typically developing participants and those with WS showed greater accuracy using the eye than mouth region, a pattern not evident in autism. Regarding structural encoding, individuals with WS showed use of configural cues under the task demands implemented in this thesis, where individuals with autism were only able to interpret featural cues. Previous evidence of similar face processing styles in WS and autism were not supported. Taken together the findings provide further insights into face perception and social functioning in WS and autism. The research used the same participants across paradigms, considered level of functioning on the autistic spectrum and included investigations of WS and autism in the same research programme. Additional to the main experimental studies, pilot data is provided to open a new line of investigation into physiological arousal associated with holding eye contact in WS. Therefore, on the basis of the experiments conducted here, a number of suggestions are made to carry the research forward in future investigations. Throughout the thesis as a whole, comparisons are made between individuals with WS and autism that further our understanding of the links between face processing and social expertise.