Sense of Agency is more sensitive to movement execution than goal achievement

Controlling one’s own movements and the resulting outcomes in the external world generates a feeling of control, i.e. the Sense of Agency (SoA). The fact that unpredicted action events reduce SoA suggests that action monitoring and SoA are related. Previous studies indicate that the separate manipulation of movement execution and goal attainment may bring about profound changes of SoA. To explore how a combined manipulation of the movement and goal–related feedbacks affects SoA, we developed a novel paradigm. Thirty healthy volunteers (15 F; age, mean ± s.e.m.: 24.1 ± 0.54 years) performed simple goal-directed actions in a mixed-reality scenario. Participants laid their hand under an inclined monitor and placed the right hand index finger between two buttons. They were asked to lower or raise the finger following a color cue and to observe a virtual hand performing the same or the opposite movement where the goal (pressing the signaled color) was attained or missed. Importantly, the virtual scene could be displayed simultaneously (0 msec delay) or after various delays (75, 150, 225, 300 msec). This way we could manipulate the two action components within the same virtual scene. After each observation, participants evaluated if the observed action was synchronous or asynchronous with their own movement as a measure of SoA (judgments of correspondence, JoC). JoC are explicit judgments of agency and rely on the same information involved in attributing an action to oneself or to someone else, but they reduce the tendency to over-attribute actions to oneself. The proportion of “synchronous JoC” answers was calculated for each participant and for each condition. Mean values for each condition were entered in a 2x2x5 ANOVA with Movement, Goal and Delay as within-subjects factors. We found that perceived synchrony was reduced when participants observed an opposite movement independently of the duration of the delay, as highlighted by a main effect of factor Movement (F(1, 29) = 4.47, p = .043). Further a failure to attain the goal was associated with lower perceived synchrony, but only when the observed action was simultaneous (0 msec) or slightly asynchronous (delay = 75 ms), as revealed by a significant Goal x Delay interaction (F(4, 116) = 4.06, p = .004). Our results bring evidence that monitoring both movement execution and goal achievement modulates SoA. However, the relevance of these two action components appears to be time-dependent. While the contribution to SoA of goal monitoring is limited in time, the contribution of movement monitoring is not. This suggests a more constant contribution of movement execution over goal attainment to SoA.