A KINEMATIC ANALYSIS OF GOAL-DIRECTED PREHENSION MOVEMENTS EXECUTED UNDER BINOCULAR, MONOCULAR, AND MEMORY-GUIDED VIEWING CONDITIONS

Vision is critical for the efficient execution of prehension movements , providing information about: The location of a target object with re spect to the viewer; its spatial relationship to other objects; as wel l as intrinsic properties of the object such as its size and orientati on. This paper reports three experiments which examined the role playe d by binocular vision in the execution of prehension movements. Specif ically, transport and grasp kinematics were examined for prehension mo vements executed under binocular, monocular, and no vision (memory-gui ded and open-loop) viewing conditions. The results demonstrated an ove rall advantage for reaches executed under binocular vision; movement d uration and the length of the deceleration phase were longer, and move ment velocity reduced, when movements were executed with monocular vis ion. Furthermore, the results indicated that binocular vision is parti cularly important during ''selective'' reaching, that is reaching for target objects which are accompanied by flanker objects. These results are related to recent neuro psychological investigations suggesting t hat stereopsis may be critical for the visual control of prehension.