Sensory-Motor Primitives as a Basis for Imitation: Linking Perception to Action and Biology to Robotics
Imitation is a powerful means of skill acquisition, social interaction, and cultural transfer. Although the popular notion of "monkeying" and "parroting" makes the phenomenon appear ubiquitous, its more formal definition endows "true imitation" capability to very few species. We present a model of imitation that is based on a collection of direct sensory-motor mappings we call primitives, which form a strong and specialized link between the visual and motor systems, and remain the active foundation for the more complex forms of imitation and other forms of social learning. Our model is inspired and constrained by the following lines of evidence from psychophysics and neuroscience: 1) the existence of a selective attention mechanism for extracting movement information from the visual stream; 2) the existence of mirror neurons for sensory-motor integration/transformation; 3) the existence of motor primitives for structuring movement; motor primitives are a parsimonious means of encoding a basic movement vocabulary which can be composted into a broad and general movement repertoire, through the use of sequencing and superposition; and 4) the existence of a classification-based learning system, which uses the motor primitives to acquire new skills through composition and creation of new representations. The motivation and specific mechanisms of each of the parts of the model are described in detail, and related to the relevant work in both natural and synthetic (e.g., robotic) imitation, and validated in our own robotic experiments.