Both your intention and mine are reflected in the kinematics of my reach-to-grasp movement.

The aim of the present study is to ascertain whether in a social context the kinematic parameters are influenced by the stance of the participants. In particular, we consider two basic modes of social cognition, namely cooperation and competition. Naïve subjects were asked either to cooperate or to compete with a partner (a professional female actor), whose attitude could be either congruent or incongruent with the task instructions. Thus, on congruent conditions, subjects cooperated or competed with a partner showing a congruent cooperative or competitive attitude. On incongruent trials, the partner assumed an attitude that was manifestly in contrast with the instruction: competitive for the cooperative task, cooperative for the competitive task. We hypothesized that this mismatch between partner's attitude and instruction would produce a sort of unexpected social situation, affecting the kinematics of reach-to-grasp movement performed by the agents. If cooperative and competitive kinematic patterns are sensitive to the partner's attitude, then we should expect that an incongruent attitude have the potency to determine a reversal in kinematic patterning. Results revealed that for the incongruent trials the specific kinematic patterns for cooperation and competition found for the congruent conditions where modified according to the incongruent attitude assumed by the model actor. We suggest that this 'attitude' contagion is part of a sophisticated system that allows us to infer about the intention to act in a social context.