Body ownership and the motor system: rapid facilitation of embodied fake
hand movement on actual movement execution
Abstract
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 shared
sensorimotor representations of illusory and actual self-movement.