Abstract
Whether or not individuals with autism are ‘local processors’, focusing on the elements of a display rather than on the global whole, remains controversial. To examine the extent to which local elements are integrated perceptually into a global shape in autism, we first examined the ability of 10 autistic adults and matched controls to identify compound hierarchical letters (e.g. global ‘H’ made of small ‘h’s or global ‘H’ made of small ‘s’s) at the global or local level. Normal global precedence, characterized by increased interference from the global level while reporting the local elements, was observed in the control but not in the autism group. Closer scrutiny, however, suggested that a subset of autistic individuals did show global precedence (‘global’ subgroup) while a second subset (‘local’ subgroup) did not. In a second experiment, in a visual search task, the same individuals and controls detected the presence or absence of a target (composed of few or many elements), defined either by the global configuration or by the local elements, among an increasing number of distractors. While the local autism subgroup performed as well or even better than the controls at detecting the target at a local level across display size when it was made of many local elements, this was not the case for the global autism subgroup, confirming the bimodal distribution within the autism group. These results suggest that the autism population may consist of sub-populations whose predispositions for processing the local or global aspects of the visual world varies along a continuum and, as such, these findings offer a means for reconciling the apparent discrepancies in the literature.
This research was funded by a grant from the NICHD/NIDCD PO1/U19, part of the NICHD/NIDCD Collaborative Programs for Excellence in Autism.