A Divided Visual Field Approach to the Categorical Perception of Faces

The perception of boundaries between stimuli that exist along a graded continuum of physical properties is referred to as categorical perception. Categorical perception is often interpreted as evidence that language influences perception. Consistent with this, divided field studies of color and shape perception showed a relationship between categorical perception and cerebral laterality for language. Unlike color and shape perception, face recognition is associated with right-lateralized circuits in visual cortex and beyond. We hypothesized that the well-known left visual field (LVF) advantage for face recognition would show modulation by categorical versus non-categorical face perception. In two experiments, we used a divided field method in which observers performed a visual search task on arrays of faces split between the LVF and the right visual field (RVF). The search tasks required visual discrimination of faces by virtue of either identity or gender. Our results confirmed the existence of categorical face perception in both types of task. Crucially, however, we found greater categorical perception of identity for LVF faces and the opposite (RVF) for categorical perception of face gender. Our findings show that categorical effects on face recognition depend on opponent cerebral laterality for language and the visual processing of faces