Why is visual search superior in autism spectrum disorder?

This study investigated the possibility that enhanced memory for rejected distractor locations underlies the superior visual search skills exhibited by individuals with autism spectrum disorder (ASD). We compared the performance of 21 children with ASD and 21 age- and IQ-matched typically developing (TD) children in a standard static search task and a dynamic search task, in which targets and distractors randomly changed locations every 500 ms, precluding the use of memory in search. Children with ASD exhibited overall faster reaction time (RT) relative to TD children, and showed no disruption in search efficiency in the dynamic condition, discounting the possibility that memory for rejected distractors augments their visual search abilities. Analyses of RT x set size functions showed no group differences in slopes but lower intercepts for the ASD group in both static and dynamic search, suggesting that the ASD advantage derived from non-search processes, such as an enhanced ability to discriminate between targets and distractors at the locus of attention. Eye-movement analyses revealed that the ASD and TD groups were similar in the number and spatial distribution of fixations across the search array, but that fixation duration was significantly shorter among children with ASD. Lower intercepts in static search were related to increased symptom severity in children with ASD. In summary, ASD search superiority did not derive from differences in the manner in which individuals with ASD deployed their attention while searching, but from anomalously enhanced perception of stimulus features, which was in turn positively associated with autism symptom severity.