Wagman Jeffrey B, Abney Drew H, Rosenbaum David A
Department of Psychology, Illinois State University, Normal, IL, USA.
Department of Psychology, Indiana University, Bloomington, IN, USA.
Hum Mov Sci. 2018 Feb;57:451-460. doi: 10.1016/j.humov.2017.10.009. Epub 2017 Oct 23.
Previous studies have shown that people's grasps of objects are tuned to the objects' inertial properties. In most of those studies, information obtained about the attunement of the grasps to the objects' inertial properties was limited to first-order grasp planning (i.e., planning of grasps based on immediate task demands). We investigated attunement of grasps to an object's inertial properties in the context of second-order grasp planning (i.e., planning of grasps based on subsequent task demands). In Experiment 1, participants grasped a horizontal rod whose right or left end would be brought down onto a target. Consistent with previous findings, participants grasped the rod so as to complete the movement with a thumb-up posture, using an overhand grasp when the right end of the rod was to be brought to the target and an underhand grasp when the left end was to be brought to the target. They also grasped the rod to the right of center, but more so when doing this with an underhand than when with an overhand grasp. In Experiment 2, participants performed the same task with an asymmetrically weighted rod. Changes in subjects' grasps in Experiment 2 compared to Experiment 1 suggested that participants grasped the rod based on the inertial properties of the rod in a way that took advantage of the pendular properties of the hand-plus-object.
先前的研究表明，人们对物体的抓握会根据物体的惯性属性进行调整。在大多数此类研究中，关于抓握对物体惯性属性的调整所获得的信息仅限于一阶抓握规划（即基于即时任务需求的抓握规划）。我们在二阶抓握规划（即基于后续任务需求的抓握规划）的背景下，研究了抓握对物体惯性属性的调整。在实验1中，参与者抓握一根水平杆，杆的右端或左端会被向下放置到一个目标上。与先前的研究结果一致，参与者抓握杆的方式是为了以拇指向上的姿势完成动作，当杆的右端要被放置到目标上时使用正手抓握，当左端要被放置到目标上时使用反手抓握。他们还会在杆的中心右侧抓握杆，但反手抓握时比正手抓握时抓得更靠右。在实验2中，参与者使用一根不对称加权的杆执行相同的任务。与实验1相比，实验2中参与者抓握方式的变化表明，参与者根据杆的惯性属性抓握杆，利用了手部加物体的摆动特性。
