Experience-based priming of body parts: a study of action imitation.

Two important dimensions of action are the movement and the body part with which the movement is effected. Experiment 1 tested whether automatic imitation is sensitive to the body part dimension of action. We found that hand and foot movements were selectively primed by observation of a corresponding, task-irrelevant effector in motion. Experiment 2 used this body part priming effect to investigate the role of sensorimotor learning in the development of imitation. The results showed that incompatible training, in which observation of hand movements was paired with execution of foot movements and vice versa, led to a greater reduction in body part priming than compatible training, in which subjects experienced typical contingencies between observation and execution of hand and foot movements. These findings are consistent with the assumption that overt behavioral imitation is mediated by the mirror neuron system, which is somatotopically organized. Our results also support the hypothesis that the development of imitation and the mirror neuron system are driven by correlated sensorimotor learning.