Task-irrelevant object response to action enhances the sense of agency for controlling the object in automation

The sense of agency (SoA) refers to the experience of controlling our bodies and tools. Recent automated systems require the operators to have less manual control, which decreases the SoA. This study investigated how to increase the SoA when operating automated systems, by focusing on the effect of an object's responses to operators' actions on the SoA. Participants applied brakes to a moving black circle by pressing a key, in order to stop the circle near a goal. Then, they estimated their SoA for stopping the circle. We informed them that there were automatic control trials in which the circle stopped independently of their keypress (86% of the trials). The circle's color briefly changed to white (i.e., flashed) when they pressed the key in a half of the automatic control trials. The SoA was higher with the flash than without it. However, the SoA neither increased when the circle flashed independently of a keypress nor when another object flashed due to a keypress. Furthermore, the keypress contingent object-flash did not influence the SoA when the participants controlled the circle manually. These results indicated that spatiotemporally contingent object responses to actions can enhance the SoA in automatic control situations.