An essential reconsideration of one of the most far-reaching theories in modern neuroscience and psychology. In 1992, a group of neuroscientists from Parma, Italy, reported a new class of brain cells discovered in the motor cortex of the macaque monkey. These cells, later dubbed mirror neurons, responded equally well during the monkey’s own motor actions, such as grabbing an object, and while the monkey watched someone else perform similar motor actions. Researchers speculated that the neurons allowed the monkey to understand others by simulating their actions in its own brain. Mirror neurons soon jumped species and took human neuroscience and psychology by storm. In the late 1990s theorists showed how the cells provided an elegantly simple new way to explain the evolution of language, the development of human empathy, and the neural foundation of autism. In the years that followed, a stream of scientific studies implicated mirror neurons in everything from schizophrenia and drug abuse to sexual orientation and contagious yawning.