Local bias and local-to-global interference without global deficit: a robust finding in autism under various conditions of attention, exposure time, and visual angle.

A wide variety of paradigms have shown that autistic individuals present with superior performance on visual tasks. Here, the impact of task constraints on visual hierarchical processing in autism was investigated. By employing free- and forced-choice procedures, global and local processing of Navon-type hierarchical numerals was examined in 15 autistic persons (13 males, 2 females) and a comparison group. In the free-choice condition, autistics chose global and local targets randomly, though they were faster responding to local than to global targets, regardless of visual angle and exposure duration. In contrast, the comparison group exhibited a global advantage in naming time, which was evident only for shorter exposures, as well as effects of visual angle. In the forced-choice condition, autistics presented with a more important local-to-global interference than global-to-local interference, whereas the comparison group exhibited global advantage and bidirectional interference. Overall, the autistic participants presented with atypical local-to-global interference and local advantage in incongruent conditions (where global and local targets differ), in naming time as well as accuracy. The relative insensitivity of local bias to task constraints in autistics, in comparison to nonautistic participants, indicates that local bias, with local-to-global interference, is a key and characteristic feature of autistic visual cognition and a strong candidate for the "endophenotype" of autism.