Alternating images of congruent and incongruent movement creates the illusion of agency

We report a novel illusion whereby people perceive both congruent and incongruent hand motions as a united, single, and continuous motion of one's own hand (i.e. a sense of agency). This arises when individuals watch congruent and incongruent hand motions alternately from a first person perspective. Despite an individual knowing that s/he is not performing the motion, this illusion still can arise. Although a sense of agency might require congruency between predicted and actual movements, united motion is incongruent with predicted movement because the motion contains oscillating movement which results from switching hand movement images. This illusion offers new insights into the integration mechanism of predicted and observed movements on agency judgment. We investigated this illusion from a subjective experience point of view and from a motion response point of view.