Observer's body posture affects processing of other humans' actions

Action observation triggers by default a mental simulation of action unfolding in time. We assumed that this simulation is "embodied": the body is the medium through which observer's sensorimotor modalities simulate the observed action. The participants in two experiments observed videos, each depicting the central part of an action performed by an actress on an object (e.g., answering the phone) and soon after each video they observed a photo portraying a state of the action not observed in the video, either depicting the initial part or the final part of the whole action. Their task was to evaluate whether the photo portrayed something before (backward photo) or after the action in the video (forward photo). Results showed that evaluation of forward photos was faster than evaluation of backward photos (Experiment 1). Crucially, participants' body posture modulated this effect: keeping the hands crossed behind the back interfered with forward simulations (Experiment 2). These results speak about the role of the observer's body posture in processing other people's actions.