Body Ownership and the Motor System: Rapid Facilitation of Embodied Fake Hand Movement on Actual Movement Execution

Body ownership—the perception that one's body belongs to oneself—has been explored using a rubber hand illusion, in which individuals misperceive a fake hand as their own (i.e., embodiment of the fake hand) when an unseen real hand and a visible fake hand are stroked synchronously. Thus, the movement of an embodied fake body may be represented in one's own sensorimotor system. Using a combination of the rubber hand illusion and a motor task, we investigated whether simple movement of the embodied fake hand influenced the subsequent movement of the participants' hand. The participants lifted their own index finger immediately upon observing the index finger lifting on the embodied (rubber hand illusion) or non‐embodied (non‐rubber hand illusion) fake hand (Experiment 1), and a light‐emitting diode turning on near the fake hand (Experiment 2). The reaction times, peak velocities, and peak acceleration were extracted from the participants' finger‐lifting movements. In Experiment 1, the reaction time was significantly shorter in the rubber hand illusion condition than in the non‐rubber hand illusion condition, suggesting the rapid facilitation effect of embodied fake hand movement on actual movement. However, no such motor facilitation was observed in Experiment 2, confirming that the improved reaction time in Experiment 1 resulted from the visual movement of the fake hand rather than attention to the fake hand itself. In contrast to the reaction time, the peak velocity and acceleration did not differ significantly in either experiment. These findings reflect the similar sensorimotor representations of illusory and actual self‐movement.

身体所有权（Body ownership）指个体感知自身肢体归属于自我的心理体验，常通过橡胶手错觉（rubber hand illusion）范式开展研究：当个体的真实手部处于不可见状态、可见的假手部与真实手部接受同步触觉刺激时，个体易将假手误判为自身肢体（即假手的具身化（embodiment））。由此可见，具身化的假肢体运动可在个体自身的感觉运动系统（sensorimotor system）中得到表征。本研究结合橡胶手错觉范式与运动任务，探究具身化假手的简单运动是否会影响参与者自身手部的后续运动。实验1中，参与者在观察具身化（橡胶手错觉条件）或非具身化（非橡胶手错觉条件）假手的食指抬起动作时，需立即抬起自身食指；实验2中，则在假手附近的发光二极管（light-emitting diode, LED）亮起时执行相同动作。研究提取了参与者抬食指动作的反应时（reaction times）、峰值速度（peak velocities）与峰值加速度（peak acceleration）作为观测指标。实验1结果显示，橡胶手错觉条件下的反应时显著短于非橡胶手错觉条件，表明具身化假手的运动可对真实肢体运动产生快速易化效应。但实验2未观察到此类运动易化效应，由此证实实验1中反应时的缩短源于假手运动的视觉刺激，而非对假手本身的注意力分配。与反应时结果不同，两项实验中峰值速度与峰值加速度均无显著差异。上述结果表明，错觉性自我运动与真实自我运动共享相似的感觉运动表征。