Feeling of agency versus judgment of agency in passive movements with various delays from the stimulus

Background. The sense of agency (SoA) provides us with the experience of be­ing a physical agent with free will. On a phenomenological basis, SoA can be di­vided into sensory components (feeling of agency, FoA) and more cognitive com­ponents (judgment of agency, JoA). Both these components can be independently measured. Objective and Method. A new method was developed to test the possibility of preserving SoA and its components in the atypical conditions of passive movements. Parameters of the participant’s movement in response to a visual stimulus (reaction time, speed, and amplitude) were measured and used to control a servo that simu­lated the movement (executed passive movements). The scores on the psychometric scale of the agency and the event-related potentials (ERPs) were recorded for variable movement delays relative to the stimulus onset. Results. It was found that the FoA was not present under passive movement con­ditions. At the same time, participants associated these movements with their own activity (JoA), even when their delay after the stimulus onset was too short to be ac­tively reproduced. The somatosensory ERPs’ amplitude decreased for the expected movements, demonstrating an inverse relationship with the agency scores. The lowest amplitude was observed when movements were actuated by another hand. The results can be explained using a predictive forward model, since the FoA was not observed in the absence of active movements. On the other hand, the ERPs’ data and the presence of JoA with various delays between the stimulus and movement support the postdic­tive model of agency, where the leading role is assigned to prejudice and contextual knowledge related to the action. Conclusion. It seems that the “context pressure” of the situation, demanding a mandatory response to the stimulus, forms a cognitive prediction of movements without firm sensory representation.