Perception and action in social interactions are based upon the visual but not motor system

Background: It is commonly assumed that action recognition in social interactions is mediated by a single and primarily motor based mechanism. Yet other influential theories assume that vision for perception and vision for action are mediated by different visual processes (Milner Goodale, 2008). Does the observation of actions and the interaction with an interaction partner in social interaction rely on the same motor based recognition mechanism? We examined the response properties of action representations in observational and interactive social scenarios. Experiment 1 examined action representations and their sensitivity to influences from the visual and motor system. Experiment 2 examined the influence of visual action representations on action production in social interactions. Methods: We measured the response properties of neural action recognition processes by means of behavioral adaptation. To probe participants’ action discrimination ability, participants discriminated morphed actions. Results: Experiment 1: We found that the repeated viewing (visual action adaptation) and the repeated execution of actions (non-visual motor adaptation) changed participants’ perception of ambiguous actions, demonstrating the influence of the motor and visual system on action recognition. Yet when participants were visually and motorically adapted at the same time (akin to simultaneous action observation and action execution in social interactions) only visual action adaptation was able to alter participants perception. Experiment 2: Visual action representations influence action production (by measuring participants’ movement trajectories) only when participants execute and observe actions at the same time. Conclusion: These results suggest that action and perception in social interaction is mainly driven by the visual system. Moreover, we suggest different action recognition mechanisms for observing an action and interacting with an interaction partner