Ansuini Caterina, Cavallo Andrea, Koul Atesh, D'Ausilio Alessandro, Taverna Laura, Becchio Cristina
Department of Robotics, Brain and Cognitive Sciences, Fondazione Istituto Italiano di Tecnologia.
Department of Psychology, University of Torino.
J Exp Psychol Hum Percept Perform. 2016 Jul;42(7):918-29. doi: 10.1037/xhp0000169. Epub 2016 Apr 14.
During reach-to-grasp movements, the hand is gradually molded to conform to the size and shape of the object to be grasped. Yet the ability to glean information about object properties by observing grasping movements is poorly understood. In this study, we capitalized on the effect of object size to investigate the ability to discriminate the size of an invisible object from movement kinematics. The study consisted of 2 phases. In the first action execution phase, to assess grip scaling, we recorded and analyzed reach-to-grasp movements performed toward differently sized objects. In the second action observation phase, video clips of the corresponding movements were presented to participants in a two-alternative forced-choice task. To probe discrimination performance over time, videos were edited to provide selective vision of different periods from 2 viewpoints. Separate analyses were conducted to determine how the participants' ability to discriminate between stimulus alternatives (Type I sensitivity) and their metacognitive ability to discriminate between correct and incorrect responses (Type II sensitivity) varied over time and viewpoint. We found that as early as 80 ms after movement onset, participants were able to discriminate object size from the observation of grasping movements delivered from the lateral viewpoint. For both viewpoints, information pickup closely matched the evolution of the hand's kinematics, reaching an almost perfect performance well before the fingers made contact with the object (60% of movement duration). These findings suggest that observers are able to decode object size from kinematic sources specified early on in the movement. (PsycINFO Database Record
在伸手抓握动作过程中，手会逐渐塑形以适应要抓握物体的大小和形状。然而，通过观察抓握动作来收集物体属性信息的能力却鲜为人知。在本研究中，我们利用物体大小的影响来探究从运动运动学中辨别不可见物体大小的能力。该研究包括两个阶段。在第一个动作执行阶段，为了评估抓握缩放，我们记录并分析了朝向不同大小物体的伸手抓握动作。在第二个动作观察阶段，相应动作的视频片段以二选一的强制选择任务呈现给参与者。为了探究随时间变化的辨别性能，视频经过编辑以从两个视角提供不同时间段的选择性视觉。进行了单独分析以确定参与者辨别刺激选项的能力（I型敏感性）以及他们辨别正确和错误反应的元认知能力（II型敏感性）如何随时间和视角变化。我们发现，早在运动开始后80毫秒，参与者就能从侧面视角观察到的抓握动作中辨别物体大小。对于两个视角，信息提取与手部运动学的演变紧密匹配，在手指接触物体之前（运动持续时间的60%）就达到了近乎完美的表现。这些发现表明，观察者能够从运动早期指定的运动学来源中解码物体大小。（PsycINFO数据库记录）
