Contextual movement constraints of others modulate motor preparation in the observer.

Previous research demonstrated that observing an action seems to automatically activate a corresponding motor representation in the observer. It has been argued that this direct matching of observed on executed actions is modulated by contextual factors. An open question is whether observing another person being physically restrained has an influence on action execution in the observer. Using performance measures we found a slowing of response times when perceiving others' hands being physically restrained (Experiment 1). We did not find a slowing effect when participants responded with their feet ruling out a general perceptual interpretation of the present findings (Experiment 2). To further test our hypothesis, we measured event-related brain potentials (ERPs). The ERP results demonstrate that the observed slowing effect is reflected in a decrease of motor-related ERP components (Experiment 3). Perceiving others' hands physically restrained impairs motor preparation in the observer. Our findings suggest that observed environmental constraints are automatically mapped onto the observer's motor system. Such a mapping of motor restraints might facilitate action understanding.