Between-object action coupling influences visual selection: Neuropsychological evidence

Visual extinction, associated with unilateral parietal damage, occurs when a patient can report a single unilateral stimulus but fails to report the same stimulus under bilateral presentation conditions. Prior studies have shwn that extinction can be reduced if bilateral stimuli group to form parts of a single object. In this study we demonstrate that extinction can also be reduced in parietal patients when separate objects fall in appropriate spatial relations for action. We failed to find similar reductions in extinction when stimuli were associatively but not action-related, and we failed to find effects of action relations when words rather than objects were presented to patients. The evidence suggests that action coupling can be used to 'glue' objects together for visual selection.