Visual Search Cancellation at 36 Months in Autism: Search Strategies and Infant Predictors

Background:   Enhanced visual search is one of the most replicated findings in the autism spectrum disorders (ASD) literature and has been documented as young as in infancy and toddlerhood. Visual search in this context often refers to locating one target amongst distracters—less research has investigated search strategies when there are multiple targets amongst distracters, and no studies to our knowledge have manipulated targets and distracters to investigate varying search strategies based on task requirements. It is possible that in ASD performance will be poorer in a multiple target cancellation task, in particular when targets represent a conceptual category as opposed to an exemplar and thus require conceptual knowledge. In contrast, it is possible that performance will be enhanced when exemplar targets are perceptually similar to distracters, thus requiring perceptual abilities known to be enhanced in ASD.

Objectives:  This study sought to investigate cancellation performance in 36-month-olds at high and low risk for autism. Additionally, visual search performance for single targets earlier in childhood were used to predict cancellation performance at 36 months to determine if the abilities underlying single target visual search relate to cancellation performance.

Methods:   Sixty-two 36-month-olds at high and low risk for ASD participated in the visual search cancellation task on a touchscreen monitor as a part of a battery of cognitive tasks. In this task, children were asked to search for and touch a) cats among inanimate objects (baseline, “exemplar search”), b) animals amongst inanimate objects (to test categorization, such that higher autistic symptoms were hypothesized to relate to worse performance, “conceptual search”), and c) dogs amongst furniture (to test for the ability to discriminate between perceptually similar objects, such that higher autistic symptoms were hypothesized to relate to better performance, “perceptual search”). The Autism Diagnostic Observation Scale (ADOS) was used to assess severity of autism symptoms.

Results:   While controlling for motor and language abilities, ADOS social affect (SA) scores related to the difference between exemplar and conceptual search conditions in a combined measure of speed and accuracy, with poorer search related to high SA scores. To understand the origins of poor performance, we analyzed search strategies. Interestingly, ADOS repetitive and restrictive behavior (RRB) scores related to spatial search efficiency specifically in conceptual search, with more efficient search related to higher RRB scores. This may be due to children with low autistic symptoms using a conceptual strategy (all the camels are touched then all the bears, etc.), which is still strategic but not spatially efficient. There is some evidence for this hypothesis, with a negative relationship between measures of conceptual strategy and spatial strategy. Finally, there is a marginal negative relationship between single target visual search at 24 months and spatial search efficiency in conceptual search.

Conclusions:   High autistic symptoms show counterintuitive continuous relationships with both poorer speed/accuracy as well as better spatial search efficiency. These relationships may be explained by poor conceptual knowledge resulting in less conceptually driven search.