Project Summary Individuals suffering from Autism Spectrum Disorder (ASD) show accelerated learning in some perceptual tasks, but deficits in perceptual learning and the ability to generalize learning to novel situations. Perceptual deficits likely reflect abnormalities in cortical structure and function in individuals with ASD, and they may underlie (or exacerbate) many of the social and communicative deficits that define ASD. In particular, the abilities to perceptually categorize facial expressions, speech sounds, prosody, and gestural movements that children acquire during development are a prerequisite for normal language and social skills to emerge. Therefore, understanding the perceptual learning deficits associated with ASD may help us better understand and ameliorate communicative and social impairments. However, the research so far directly examining categorization and perceptual learning in ASD individuals has produced mixed findings and shows strong indications of important effects of individual differences. Recent simulations with connectionist models of visual cortical processing and pilot data comparing learning with and without feedback suggest a way to explain the diverse findings across studies and individuals. Specifically, these models and data suggest that deficits in basic neural plasticity mechanisms (experience dependent changes in cortical neural connections) particularly under conditions of learning from attentive exposure can account for atypical perceptual category learning shown by high functioning (HF) children and adults with ASD. There are two general aims of this project. They are designed to lay a solid foundation for future work that could fully develop neurally-grounded cognitive processing theories of ASD, and translational training protocols to help facilitate learning by children with ASD. The first is to explore perceptual learning when learning from exposure versus learning with feedback and to determine whether abnormalities found when learning complex visual perceptual categories also extend to perceptual learning of basic perceptual discriminations and to the auditory modality. The second aim is to examine whether progressive typicality ordering of stimuli affects learning in either or both learning conditions and whether that is true for all levels and modalities studied. Four experiments will be conducted using variants of a basic perceptual learning methodology comparing learning from exposure versus with direct training. Two experiments will use visual stimuli and two auditory. Two will look at family resemblance category learning and two will examine perceptual discrimination learning. These experiments will test the following hypotheses derived from past simulations and experiments: unlike typically developing children, (1) training regimens involving feedback will produce much greater learning than learning from exposure in HF children with ASD; (2) HF children with ASD will show an advantage of ...