Intact Use of Prior Information in Autism during Visual Search

Background: Visual perception is influenced by prior experiences and learned expectations. One example of this is the ability to rapidly resume visual search after an interruption to the stimuli. It has recently been suggested that atypical visual perception in autism spectrum conditions (ASC) can be explained by attenuated use of prior information during perception. However, there is a current lack of empirical evidence to comprehensively evaluate this theory.

Objectives: We aimed to use an interrupted search paradigm to assess whether rapid resumption is intact in ASC. We hypothesize that attenuated use of prior information in perception would lead to a reduced ability to rapidly resume searches after interruption.

Methods: Participants with (N=24) and without ASC (N=26) were asked to complete a visual search task in which search displays were periodically interrupted by blank displays. Participants were required to locate a ‘T’ shaped target amongst ‘L’ shaped distractors and to report its color. Search displays contained either 16 or 32 distractors. During trials the search display would only be visible for 100ms presentations separated by a 900ms blank display. Participants completed a total of 300 trials, divided across 10 blocks.

Results: Reaction time distributions were normalized separately for responses occurring between the first and second exposures of displays and responses occurring after subsequent exposures. In both groups the distribution of responses immediately following the first exposure differed significantly from the distribution of responses following subsequent exposures (p<.001). Responses following subsequent exposures were found to be bimodally distributed, consisting of a combination of faster trials (in which prior exposure to the display facilitate search) and standard trials. An Expectation-Maximisation algorithm was used to fit a 2-component Gaussian mixture model to the bimodal data. This model was used to identify trials in which participates were influenced by prior exposures to the search display. We found no difference in the relative proportion of fast and standard trials between the two groups (p>.3).

Conclusions: Our results suggest that individuals with ASC show intact use of prior information during visual search. These findings are in contrast to the claims that individuals with ASC show attenuated use of prior information during perception.