Visual Search in Time Among Persons with an Autism Spectrum Disorder

Background: Individuals with an Autism Spectrum Disorder  (ASD) demonstrate specific strengths in attention that includes the ability to detect visual stimuli among distractors. This visual search strength has generally been studied using static conjunctive search tasks, in which participants search for a target (e.g. orange squares) among distractors that share features with it (e.g. orange circles and blue squares).  Here we look at the integrity of temporal visual search through single and dual target search tasks, and focus on the attentional blink (AB) in dual target searches. The AB is a phenomenon whereby the second of two targets is often missed when it follows the first target by 200-500ms.

Objectives: To extend findings on enhanced visual search from the spatial domain to the temporal domain in both single and dual target search experiments and to assess the integrity of the AB, and it’s associated characteristics.

Methods: 15 participants with an ASD (ADOS and ADI-R confirmed) and 15 typically developing (TD) children and adolescents matched on the basis of age and IQ completed 4 experimental tasks in counterbalanced order. On the multispeed tasks (current N = 7, analysis underway for the remaining participants), participants were asked to detect 1 target (either a purple letter among white letters: featural task (exp 1.), or a letter among numbers: category task, exp.2). 29 distractors, and 1 target were presented at slow (135ms/stimulus), medium (102.5ms/stimulus) and fast (83ms/stimulus) speeds and participants had to report the correct target at the end of the stream. In the AB tasks (exp 3 and 4, N = 15 participants anlayzed), participants reported two targets (the T1 and T2), which consisted of either 2 purple letters among white letters (featural AB task) or 2 letters among numbers (categorical AB task).

Results: Performance on experiments 1 and 2 was more accurate among individuals with an ASD compared to TD participants, and this was especially evident at the fastest speed. On the AB tasks, participants’ ability to detect the first of 2 targets did not differ between the groups for either experimental task. For T2|T1 (conditional accuracy: the accuracy with which participants correctly identified the T2 given correct T1 identification), task and group differences emerged. The AB was more pronounced overall in the category task compared to the feature task for both groups, and was less pronounced in ASD on the feature task and more pronounced on the category task relative to the TD participants. Additional characteristics of the AB, including swaps (in which participants identify both targets correctly but reverse their order) appeared over longer lags among persons with ASD, whereas binding errors, in which participants falsely report the target as the distractor preceding or following the target (by 1 or 2 lags) did not differ between the groups.

Conclusions: Strengths in visual search were noted for the multispeed tasks however more subtle group differences were noted on AB tasks. These findings will be discussed with respect to current theories of the AB and ASD.