Mirror neurons may hold the brain’s key to social interaction: each coding not only a particular action or emotion, but also the recognition of that action or emotion in others. The Mirror System Hypothesis adds an evolutionary arrow to the story: from the mirror system for hand actions, shared with monkeys and chimpanzees, to the uniquely human mirror system for language. In this volume, written to be accessible to a wide audience, experts from child development, computer science, linguistics, neuroscience, primatology, and robotics present and analyze the mirror system and show how studies of action and language can illuminate each other.