Intersubjective action-effect binding: eye contact modulates acquisition of bidirectional association between our and others' actions.

In everyday social life, we predict others' actions in response to our own actions. Subsequently, on the basis of these predictions, we control our actions to attain desired social outcomes and/or adjust our actions to accommodate the anticipated actions of the others. Representation of the bidirectional association between our and others' actions, that is, intersubjective action-effect binding, could make such intersubjective action control easier and smoother. The present study investigated not only whether or not intersubjective action-effect binding was acquired but also whether or not eye contact modulated it. Experiment 1 showed that after a repeated experience during which participants' finger movements triggered a target female individual's mouth gesture, observing the target's mouth gestures came to automatically trigger the participants' finger movements. Experiments 2 and 3 revealed that this effect was not observed when the target's gaze direction was averted (Experiment 2) or when the target's eyes were closed (Experiment 3) throughout the acquisition phase. These results indicate that intersubjective action-effect binding occurs and that an ostensive signal, that is, eye contact modulates it.