Abstract
Goal. Autism spectrum disorders (ASD) are neurodevelopmental disorders characterized by deficits in social and communication skills, and repetitive behaviors. Sensory perception is reportedly atypical in ASD, marked by poor global form processing. Previous studies have found impaired performance on a variety of global processing tasks in ASD, but results are inconsistent. We employed an objective task with limited verbal instructions to assess global form processing in ASD. Methods. We used shape match-to-sample task in which participants saw a real – bounded – form followed by a pair of Kanizsa Illusory Contours (KIC) (subjective shapes induced from local "pacman" elements); their task was to indicate which KIC shape matched the previously displayed real sample shape. The stimuli were presented on a touch-sensitive display; eye position was monitored throughout. Non-contingent positive feedback was provided to maintain motivation. We compared performance across three populations: those with a confirmed diagnosis of ASD, those with a diagnosis of Attention Deficit-Hyperactivity Disorder (ADHD), and typically developing children (NT). Participant age ranged from 4 years to adulthood. Results. 22 participants (13 ASD, 4 ADHD, and 5 NT) completed testing. Accuracy increased with age within all three groups, with 5-6 year-olds performing below criterion (80% correct) and all groups reaching plateau by 10-13 years. Performance of the ADHD and NT groups was superior to the ASD group prior to age 10 years. The youngest children were more likely to touch the pacmen than the center, suggesting a local perceptual strategy, rather than the global strategy of older children. ASD children were less likely to touch the center than the other groups before age 10. Response time decreased similarly with age in all groups. Conclusion. These results demonstrate a fundamental change in perceptual ability between early and late childhood in ADHD and typical controls, which is delayed in individuals with ASD.
Meeting abstract presented at VSS 2013