title: Do children with autism perceive second-order relational features? The case of the Thatcher illusion.
abstract: BACKGROUND
  This study presents two experiments that investigated whether children with autism were susceptible to the Thatcher illusion. Perception of the Thatcher illusion requires being able to compute second-order configural relations for facial stimuli.
  
  
  METHODS
  In both experiments children with autism were matched for non-verbal and verbal ability with a group of children with moderate (non-specific) mental retardation (MLD) and a group of typically developing children respectively. Participants were asked to detect the 'unusual' face in a two-alternative-forced-choice version of the Margaret Thatcher illusion with grey-scale (Experiment 1) and monochrome 'Mooney' face images (Experiment 2). In Experiment 1 participants also performed a control task where buildings had been doctored in the same way as the facial stimuli.
  
  
  RESULTS
  Children with autism were as susceptible to the Thatcher illusion as both control groups, in terms of accuracy and reaction time to make decisions about which face was unusual. Children with autism performed more accurately than children with MLD in the buildings task.
  
  
  CONCLUSIONS
  Children with autism are able to compute second-order configural features in faces and exhibit no difference in face processing, relative to appropriate control groups.
authors.affiliation: Centre for Behavioural Research, Analysis and Intervention in Developmental Disabilities, School of Psychology, University of Southampton, UK.
authors.forename: Helen
authors.initials: H
authors.lastname: Rouse
authors.forename: Nick
authors.initials: N
authors.lastname: Donnelly
authors.forename: Julie A
authors.initials: JA
authors.lastname: Hadwin
authors.forename: Tony
authors.initials: T
authors.lastname: Brown
mesh_terms: D001321:Autistic Disorder / Q000150:complications* / Q000503:physiopathology*; D002648:Child; D003657:Decision Making; D005145:Face; D005260:Female; D006801:Humans; D008297:Male; D009903:Optical Illusions; D021641:Recognition, Psychology; D014796:Visual Perception