Implicit but not Explicit Feature Binding in a Balint's Patient

Abstract

Visual perception is often conceptualized as a process of extracting visual attributes from the stimulus, from simple features like colour and orientation to high-level identities of words and objects. However, an important further task forvision is to solve the “binding problem”—to determinewhich visual attributes go together to form one object (e.g. Treisman & Gelade, 1980). Recent evidence suggests thatthe parietal lobes are critical forfeaturebinding (e.g.Friedman-Hill, Robertson, & Treisman, 1995). We examined a patient with bilateral parietooccipital damage and found that, while he was at chance on an explicit binding task (reporting which of two words was coloured), an implicit reaction time measure showed thatcorrectcolour-word bindings were nonetheless represented in his visual system. These results (1) show a dissociation between implicit and explicit binding and (2) suggest that the parietal lobes may be critical for explicit but not implicit binding. The implications of these results for feature integration theory are discussed.