The Mirror System Hypothesis: from a Macaque-like Mirror System to Imitation

The Mirror System Hypothesis (MSH) of the evolution of brain mechanisms supporting language distinguishes a monkey-like mirror neuron system from a chimpanzee-like mirror system that supports simple imitation and a human-like mirror system that supports complex imitation and language. This paper briefly reviews the seven evolutionary stages posited by MSH and then focuses on the early stages which precede but are claimed to ground language. It introduces MNS2, a new model of action recognition learning by mirror neurons of the macaque brain to address data on audio-visual mirror neurons. In addition, the paper offers an explicit hypothesis on how to embed a macaque-like mirror system in a larger human-like circuit which has the capacity for imitation by both direct and indirect routes. Implications for the study of speech are briefly noted.