New in softcover. Hardcover was published in 2013. Linguists continue to argue about what recursion actually is, leading to the central dilemma: is full recursion, as defined by mathematicians, really necessary for human language? This book defines the elusive construct with the goal of furthering research into language and cognition. An up-to-date literature review surveys extensive findings based on non-verbal communication devices and neuroimaging techniques. Comparing human and non-human primate communication, the book's contributors examine meaning in chimpanzee calls, and consider the possibility of a specific brain structure for recursion. The implications are then extended to formal grammars associated with artificial intelligence, and to the question of whether recursion is a valid concept at all.