Grouping Interference in ASD: Evidence from a Series of Multiple Object Tracking Experiments

Background: In autism spectrum research both atypical perceptual organization and inadequate motion perception have been a major topic of interest. While some studies find superior processing of local details, substandard processing of global structures, reduced sensitivity to biological motion or heightened thresholds for coherent motion in individuals with ASD, research findings on these phenomena vary widely and are often contradictory.

Objectives: In order to gain insight into these controversial phenomena, we performed a series of experiments using a modified version of the Multiple Object Tracking paradigm as designed by Scholl et al. (2001). Previously administered to adults only, MOT was designed to evaluate, in an implicit manner, to what extent grouping cues hamper tracking performance. With these experiments, we aimed to investigate the effect of connection-based grouping in typically developing (TD) children, and whether connection-based grouping had a differential effect in children with ASD.

Methods: In two behavioral experiments we presented a modification of the MOT paradigm to a group of children with ASD and to an age- and ability-matched TD group (Study 1: 6 to 10 years old, Study 2: 8 to 12 years old). In both cases participants were asked to track and distinguish four randomly moving targets from four distracters. While Study 1 administered one ungrouped and one grouped condition, Study 2 administered one ungrouped condition and two grouped conditions (visually connected with randomly placed lines vs. visually connected as closed contour). Note the ratio of ungrouped vs. grouped trials is different for Study 1 (ratio 1:1) than for Study 2 (ratio 1:2).

Results: Overall, no group difference was found comparing children with and without ASD: both participant groups showed adequate tracking abilities and both performed less in the grouped condition(s) than in ungrouped condition. However, while Study 1 found a reduced hampering effect of grouping in children with ASD compared to TD children, Study 2 failed to replicate this finding. In addition, Study 2 did not reveal any within or between group differences for both grouping conditions (randomly connected vs. connected as a closed contour). With regards to overall MOT performance, correlations were found with general Social Responsiveness Scale scores for both the TD and ASD group.

Conclusions: Firstly, the present experiments demonstrate that grouping cues have a similar impact on tracking performance in TD young children, as what was previously shown in TD adults. Secondly, results reveal mixed evidence in terms of the hampering effect of grouping cues on tracking ability in ASD. A significantly reduced interference effect of grouping in ASD was only found in the case of an equal distribution of ungrouped vs. grouped trials. Results suggest that atypical visual processing in ASD is dependent on the specific task and stimulus set. Our results challenge the idea of a general visual processing deficit in ASD, but point in the direction of a qualitative difference in visual processing.