Individuals with autism experience stronger visual capture by shape singletons than neurotypicals

摘要

Individuals with autism spectrum disorder (ASD) have been reported to perform differently than neurotypical individuals on a variety of visual tasks, including visual search (e.g., Joseph, Keehn, Connolly, Wolfe, & Horowitz, 2009). Accounts of perceptual processing in ASD differ, with influential theories arguing either that these effects are attributable to abnormal bottom-up processing or to abnormal top-down executive control and attentional processes. Here we explored the roles of bottom-up and top-down processing during visual search in participants with ASD and neurotypical controls. In traditional conjunction search tasks, targets share one feature with half of the distractors and a different feature with the other half. When the ratio of distractor types varies, reaction times (RTs) are fastest when either distractor group is small and increase until the distractor groups are equal (the distractor ratio effect). This effect is presumed to be driven primarily by bottom-up signals related to the salience of items in the smaller group. Here, we manipulated distractor color and orientation. Search arrays contained 21 items: one red horizontal target and varying numbers of red tilted and green horizontal distractors. To instill a top-down preference for optimizing search efficiency via color grouping, red distractors were the minority in a greater proportion of trials (Sobel, Gerrie, Poole, & Kane, 2007). The expected distractor ratio effect was observed for both individuals with ASD and neurotypicals when red distractor orientation was 90� from the target orientation; as green distractors became scarce, the unique orientation of the target became increasingly salient. This effect was reduced when red distractor orientation was similar to the target orientation. However, on trials with no green distractors, the ASD group showed greater capture by the orientation singleton, suggesting that visual capture can more effectively overrule a previously established top-down strategy for people with ASD than for neurotypicals.