Clinical Psychology

ii Much research to date has been devoted to understanding the neurocognitive abnormalities characteristic of autism spectrum disorders (ASD). Abnormalities in visual attention are particularly notable in ASD and have the potential to inform an understanding of the aberrant neural networks underlying this disorder. The current study utilized a model integrating components of both a two-stage model of perceptual binding and Posner’s model of attention in order to provide a coherent account of previous findings of both enhanced and impaired visual attention abilities in ASD. To investigate a potential deficit in attention shifting underlying a variety of observed attentional abnormalities in ASD, the present study employed experimental paradigms requiring attentional shifting at two levels of visual information processing. Aims of the current study were (1) to investigate a general deficit in shifting attention at the level of both preattention and focused attention in ASD as compared to age- and gender-matched NT controls, as measured by both a visual search task with a dimensional shift component and a Navon-type letter task requiring participants to shif