Effect of distorted visual feedback on the sense of agency.

It has been hypothesized that an internal model is involved in controlling and recognizing one's own actions (action attribution). This results from a comparison process between the predicted sensory feedback of the action and its real sensory consequences. The aim of the present study is to distinguish the respective importance of two action parameters (time and direction) on such an attribution judgment. We used a device that allows introduction of discordance between the movements actually performed and the sensory feedback displayed on a computer screen. Participants were asked to judge whether they were viewing 1) their own movements, 2) their own movements modified (spatially or temporally displaced), or 3) those of another agent (i.e, the experimenter). In fact, in all conditions they were only shown their own movements either unaltered or modified by varying amounts in space or time. Movements were only attributed to another agent when there was a high spatial discordance between participants' hand movements and sensory feedback. This study is the first to show that the direction of movements is a cardinal feature in action attribution, whereas temporal properties of movements play a less important role.