A close coupling of perception and action processes is assumed to play an important role in basic capabilities of social interaction, such as guiding attention and observation of others' behavior, coordinating the form and functions of behavior, or grounding the understanding of others' behavior in one's own experiences. In the attempt to endow artificial embodied agents with similar abilities, we present a proba- bilistic model for the integration of perception and generation of hand-arm gestures via a hierarchy of shared motor representations, allowing for combined bottom-up and top- down processing. Results from human-agent interactions are reported demonstrating the model's performance in learning, observation, imitation, and generation of gestures.