How do we know what others are thinking and feeling? Why do we weep at movies? UCLA neuroscientist Iacoboni introduces readers to the world of mirror neurons and what they imply about human empathy, which, the author says, underlies morality. Mirror neurons allow us to interpret facial expressions of pain or joy and respond appropriately. Thanks to these neurons, Iacoboni writes, [w]e have empathy for… fictional characters—we know how they’re feeling because the feeling is reproduced in us. Mirror neurons also help us learn by imitating, from newborns who instinctively copy facial gestures to adults learning a new skill. The author cites studies suggesting that when mirror neurons don’t work properly, as in autism, encouraging imitative behavior, or social mirroring, can help. More ominously, Iacoboni sees mirror neurons as implicated in addiction and finds possible implications for how we react to consumer and even political ads. Iacoboni’s expansive style and clear descriptions make for a solid introduction to cutting-edge neurobiology.