Visual Search In Autism Spectrum Disorder: A Consistent Islet of Ability?

Background: Empirical research has reliably demonstrated attention and visual processing abnormalities in individuals with Autism Spectrum Disorder (ASD). For example, individuals with ASD are faster to find a target shape within a complex design in an embedded figures task (Jarrold, Gilchrist, & Bender, 2005; Joliffe & Baron-Cohen, 2006), show a smaller divided-attention cost in a task that requires attention to multiple targets (Rutherford, Richards, Moldes, & Sekuler, 2007), are slower to disengage attention in visual orienting tasks (Landry & Bryson, 2004), and tend to prefer a detail-focused, rather than meaning-focused, processing style (Happe & Frith, 2006). Most importantly for the present study, individuals with ASD have also demonstrated better than normal visual search ability when tested using difficult visual search tasks (e.g. Plaisted, O’Riordan, & Baron- Cohen, 1998; O’Riordan & Plaisted, 2001; O’Riordan, Plaisted, Driver, & Baron-Cohen, 2001).

Objectives: The present study sought to replicate previous ASD visual search research, while examining whether amount of inhibition of return (IOR; an attentional bias away from previously inspected locations) in the aftermath of visual search may provide some explanation for enhanced visual search efficiency in ASD. It was expected that individuals with ASD would search more efficiently than typical controls, and that amount of IOR may differ between the ASD group and controls.

Methods: In a typical visual search task a participant is asked to search a display for a pre- specified target item that is sometimes present and sometimes absent. In addition to the target item, the display contains several distracter items that are present regardless of the trial type. In an easy visual search task, the distracter items appear visually dissimilar to the target item, making the target item easy to find when it is present. In a difficult visual search task, the distracter items are visually similar to the target item, and the target is harder to find when it is present (Duncan & Humphreys, 1989). In the present study, participants completed both an easy and a difficult visual search task. Both tasks also included a measure of IOR in the aftermath of visual search, creating a dual task requirement on each trial.

Results: Participants with ASD demonstrated slower overall RT on both easy and difficult search tasks. No evidence of a difference between ASD and control groups was observed in search efficiency (search time/item in search display), or amount of IOR following search.

Conclusions: The present study failed to replicate previous research on visual search in ASD. The dual-task requirement on each trial in the present study’s visual search tasks may have selectively disadvantaged the ASD group, thereby reducing ASD group search efficiency. Also, the difficult visual search task used in the present study was considerably more difficult than that used in previous research. Ongoing research will explore these factors as potential reasons for our non-replication of earlier visual search research in ASD.