Sense of agency primes manual motor responses.

Perceiving the body influences how we perceive and respond to stimuli in the world. We investigated the respective effects of different components of bodily representation--the senses of ownership and agency--on responses to simple visual stimuli. Participants viewed a video image of their hand on a computer monitor presented either in real time, or with a systematic delay. Blocks began with an induction period in which the index finger was (i) brushed, (ii) passively moved, or (iii) actively moved by the participant. Subjective reports showed that the sense of ownership over the seen hand emerged with synchronous video, regardless of the type of induction, whereas the sense of agency over the hand emerged only following synchronous video with active movement. Following induction, participants responded as quickly as possible to the onset of visual stimuli near the hand by pressing a button with their other hand. Reaction time was significantly speeded when participants had a sense of agency over their seen hand. This effect was eliminated when participants responded vocally, suggesting that it reflects priming of manual responses, rather than enhanced stimulus detection. These results suggest that vision of one's own hand-and, specifically, the sense of agency over that hand-primes manual motor responses.