Sense of Agency in Multi-Step Actions.

In our daily lives, we frequently execute actions that require several steps to bring about the outcome. However, investigations on how the sense of agency-the sense of controlling our actions and their outcomes-evolves in multi-step actions are still lacking. The purpose of the present research is to fill this gap. In the present study, the participants executed one-step, two-step, and three-step actions in which one, two, or three keys had to be pressed consecutively to generate a tone. We used sensory attenuation as an implicit measure of the sense of agency. Sensory attenuation means that self-produced sensory effects are perceived as less intense than externally generated effects. In the present experiment, sensory attenuation was measured in a psychophysical paradigm and increased in multi-step actions compared to the one-step action. We also asked the participants to explicitly rate the amount to which they felt that they had generated the tone. Ratings were highest in the one-step condition and dropped for multi-step actions, thus showing the opposite pattern of the sensory attenuation data. We assume that enhanced sensory attenuation in multi-step actions could be due to increased effort or more accurate sensorimotor predictions of action effects. The decrease in explicit ratings for multi-step actions might be attributed to reduced perception of causality.