What is it about the human mind that accounts for the fact that we can speak and understand a language? Why cant other creatures do the same? And what does this tell us about the rest of human abilities? Recent dramatic discoveries in linguistics and psychology provide intriguing answers to these age-old mysteries. In this fascinating book, Ray Jackendoff emphasizes the grammatical commonalities across languages, both spoken and signed, and discusses the implications for our understanding of language acquisition and loss.