Signed languages provide a powerful tool for investigating the nature of human language and language processing, the relation between cognition and language, and the neural organization of language. The value of sign languages lies in their modality. Specifically, for perception, signed languages depend upon high-level vision and motion processing systems, and for production, they require the integration of motor systems involving the hands and face. The study of signed languages allows researchers to address questions about the nature of linguistic and cognitive systems that otherwise could not be easily addressed. The book is written with the general reader with an interest in any of the major topics covered. Because it also covers basic linguistic concepts, it is appropriate as a textbook or supplementary textbook in related linguistic and cognitive science courses.