Perception and Action Lab, Department of Psychology, University of Manitoba, Winnipeg, MB, R3T 2N2, Canada.
Exp Brain Res. 2020 Jun;238(6):1433-1440. doi: 10.1007/s00221-020-05826-7. Epub 2020 May 7.
Previous investigations have uncovered a strong visual bias toward the index finger when reaching and grasping stationary or horizontally moving targets. The present research sought to explore whether the index finger or thumb would serve as a significant focus for gaze in tasks involving vertically translating targets. Participants executed right-handed reach-to-grasp movements towards upward or downward moving 2-D targets on a computer screen. When the target first appeared, participants made anticipatory fixations in the direction of the eventual movement path (i.e. well above upwardly moving targets or well below downwardly moving targets) and upon movement onset, fixations shifted toward the leading edge of the target. For upward moving targets, fixations remained toward the leading edge upon reach onset, whereas for downward moving targets, fixations shifted toward the centre of the target. The same central fixation location was observed at the time of grasp for all targets. Furthermore, for downwardly moving targets, the placement of the thumb appears to have influenced fixation location in conjunction with, not replacement of, the influence of the index finger. These findings are indicative of the increasingly relevant role of the thumb in mediating reaching and grasping downwardly moving targets.
先前的研究发现，在伸手抓取静止或水平移动的目标时，存在强烈的指向食指的视觉偏向。本研究旨在探索在涉及垂直移动目标的任务中，注视点是否会集中在食指或拇指上。参与者使用右手执行朝向计算机屏幕上向上或向下移动的 2D 目标的伸手抓取动作。当目标首次出现时，参与者会朝着最终运动路径的方向进行预期注视（即远远高于向上移动的目标或远远低于向下移动的目标），并且在运动开始时，注视点会转移到目标的前缘。对于向上移动的目标，在到达起始时注视点仍保持在前缘，而对于向下移动的目标，注视点会转移到目标的中心。对于所有目标，在抓取时都会观察到相同的中央注视位置。此外，对于向下移动的目标，拇指的位置似乎与食指的影响结合在一起，而不是替代食指的影响，共同影响注视点的位置。这些发现表明拇指在介导向下移动目标的伸手抓取中发挥着越来越重要的作用。
