Action relations, semantic relations, and familiarity of spatial position in Balint's syndrome: crossover effects on perceptual report and on localization.

We contrasted effects of the action relationship between objects, relative to effects of semantic relation and familiarity of spatial location, in a patient with Balint's syndrome. We found enhanced perceptual report of objects placed in the correct colocations for action in comparison with when the objects (1) were placed in incorrect locations for action (Experiment 1), (2) were associatively related (Experiment 2), or (3) fell in familiar locations but were not action related (Experiment 4). In contrast, the ability to localize the objects was affected by whether the objects were in familiar as opposed to unfamiliar locations with respect to one another. Action relations between objects facilitate joint attention to both objects but do not facilitate binding to location. Familiar spatial relations facilitate spatial binding, but do not cue joint attention to the stimuli. Effects of action relation on attention and localization can be dissociated from effects of semantic relationship and familiarity of spatial location on attention and localization.