Inferring another's expectation from action: the role of peripheral sensation.

It is unclear how knowledge of one's actions and one's body contribute to the understanding of others' actions. Here we show that two subjects lacking cutaneous touch and sense of movement and position show a selective deficit in interpreting another person's anticipation of weight when seeing him lifting boxes. We suggest that this ability occurs through mental simulation of action dependent on internal motor representations, which require peripheral sensation for their maintenance.