Abstract
When concurrently processing stimuli from two domains of expertise, perceptual interference is reflected as competition for shared resources. McKeeff, Tong and Gauthier (VSS 2007 submitted) found that car experts were slower than car novices to identify a face amongst irrelevant cars when all objects were presented in an RSVP stream at fixation. Here we ask whether task-irrelevant distractors from a category of expertise can also compete in the context of a visual search task where stimuli are distributed in space and observers control their eye movements. Car experts and novices searched for a target (face or sofa) in a mixed array of face, car and/or sofa distractors. The number of distractors from the target category remained constant (5), while the number of distractors from the irrelevant category varied (2, 4, or 8 distractors). Car expertise impeded search for a target face among car distractors; experts' reaction times increased as a function of the number of car distractors, while novices' reaction times remained stable regardless of distractor load. Indeed, search slopes were correlated with a quantitative measure of car expertise. Importantly, our results cannot be due to car distractors grabbing attention in car experts because we found no expertise effect when experts searched for sofas among car distractors. In car-absent conditions (searching for faces or sofas among face and sofa distractors) experts and novices also behaved similarly. Together, these data support the notion that objects of expertise automatically compete for resources supporting face processing, even when these objects are task irrelevant, visually distinct from faces, and separated in space from faces.
This work was supported by a grant from the James S. McDonnell