Abstract
Although eye-hand coordination and grasp have been studied extensively, the influence of gaze direction on the ability to align one’s hand to a seen or remembered object is unclear. In this study, we investigated how gaze direction affects location and orientation errors in a memory-guided alignment task. Participants (N=16) were asked to reach and align an elongated rectangular object to a matching rectangular outline presented at the center of a computer screen in three possible orientations: 0° (horizontal), +45° (CCW) and −45° (CW). Gaze fixation was either central or 13° left/right. The target outline was either presented briefly in complete darkness (memory task) or remained illuminated along with visual feedback of the hand (visual task). Comparing the memory task to the visual control task, there was a significant main effect of gaze location: participants aimed further to the right of the target when fixating to the left (a ‘gaze-dependent overshoot’). There was also an interaction between gaze location and orientation: when participants looked to the right, they over-rotated (too CCW for −45° and too CW for +45°), whereas when they looked to the left, they under-rotated (too CW for −45° and too CCW for +45°). In addition, there were significant interactions between task, orientation, and gaze position for variable errors. As expected, location was more precise in the visual task, and location was relatively more precise during central gaze fixation in both tasks. Likewise, orientation was more precise in the visual task, but for most target orientations central fixation only provided an advantage in the visual task. In other words, fixating a remembered target provided less advantage for orienting precision than location. Overall, our location results confirm the gaze-dependencies observed in previous pointing studies, and our orientation results reveal several additional interactions between vision, memory and gaze during manual alignment.
Acknowledgement: Canadian Institutes for Health Research