Deficit in Visual Temporal Integration in Autism Spectrum Disorders

Background: Individuals with autism spectrum disorders (ASD) are superior in processing local features. Frith and Happe conceptualize this cognitive bias as “weak central coherence," implying that a local enhancement derives from a weakness in integrating local elements into a coherent whole. The suggested deficit has been challenged, however, because individuals with ASD were not found to be inferior to normal controls in holistic perception, at least when it is required of them. In these opposing studies, however, subjects were encouraged to ignore local features and attend to the whole.

Objectives: To directly examine the ability to integrate elements into a whole image over time, we tested whether individuals with ASD are able to integrate local elements into a whole image by using slit-viewing.

Methods: Each subjects (ASD group: n=17, age 32.4 ± 8.2 years; control group: n=16, age 29.4 ± 6.9 years) named 40 figures three times, once for each of three blocks: in the first and the second block, pictures were presented behind the narrow slit (slit-viewing) at a fast and a slow speed, counterbalanced across subjects, and in the third block, whole pictures were presented in front of the slit at a fast speed (full-viewing).

Results: In the slit-viewing, the mean rates of correct answers in the ASD group (fast 46%, slow 48%) were strikingly lower than those in the control group (fast 77%, slow 75%) at both speeds, which was worsened by the absence of local salient features in the figures. By contrast, both groups successfully named almost all pictures in the full-viewing (ASD 96%, control 99%). Two-way ANOVA detected significant main effects of group (F_1,31=25.5, p<0.0001) and condition (F₂=119.0, p<0.0001), and significant interactions (F_2,62=16.2, p<0.0001).

Conclusions: The present results indicate that individuals with ASD have a clear deficit in integrating local visual information over time into a global whole, providing a direct evidence for the “weak central coherence” hypothesis.