How Special is Language?

How SPECIAL IS LANGUAGE? Doreen Kimura What the Hands Reveal about the Brain, by Howard Poizner, Edward S. Klima &Ursula Bellugi. Cambridge, MA: MIT Press. 1987. xvii &236 pp. $25. Editor's note This review article is reprinted here, with kind permission, from Language and Speech, Vol. 31, Part 4, 1988, pages 375-378. (The title, not used earlier, is used here at the reviewer's request.) The book, What the Hands Reveal. . ., is important not only because of its bearing on sign language but also because it goes to the heart of the relation between motor acts and language and the brain's control of both. The Reviews Editor and I have taken the unusual step of reprinting an already published review because we know of no one better qualified than Dr. Kimura to address the main themes of the book. The book revolves around description of six individuals who were either congenitally deaf or became deaf before the age of six. All had acquired and used a manual language system with some degree of proficiency. Subsequently, all suffered unilateral cerebral strokes, in three cases to the left hemisphere, and in three to the right hemisphere. The authors give us a detailed account of their post-stroke language abilities, as well as some information on visuo-spatial and visuoconstructional ability. Many people like myself, who have great respect for the the distinguished contribution which two of the authors (Klima & Bellugi 1979) have made to our understanding of the details of a manual language, will nevertheless be disappointed in the present book. Some contributions worthy of mention are discussed below, but, on balance, the expectations raised by the title are not realized. Two main themes run throughout the book: That the lateralization of visuo-spatial function in the brains of deaf signers is surprisingly similar to that of hearing subjects; and that the specialized function of the left hemisphere @1990 by Linstok Press, Inc. See note inside front cover. ISSN 0302-1475 79 Review: DK is explicitly tied to language. This reviewer was fairly convinced of the former before reading the book, and remains unconvinced of the latter after reading it. Despite the relating of behavioral deficits to lateralized brain lesions, the book is disturbingly abiological. There is no attempt to put manual signing in the broader context of the evolution of communication systems, and no reference to non-human studies. The position is implicitly Chomskian in approach, in that language is treated as something special, unlike any other function, and presumably uniquely human. It will appeal to those neurolinguists who believe they already know how the brain mediates language, but there is little of substance for the impartial behavioral scientist. A major premise of the book is that language is amodal, taking a form which is independent of channel or of behavioral system. Thus, both speaking and manual signing ". . . reflect the same underlying principles . . . [that] do not originate in the constraints of a particular transmission system" (p. 5); and ". . . language, independent of its transmission mechanisms, emerges in a . . . linguistically driven manner" (p. 23). One fallacy consists in assuming that the oral movements of speaking and the manual movements of signing are linked only by their employment in language systems. There is a wealth of literature on motor programming (apraxic) defects of the oral and manual musculature after left-hemisphere damage, beginning around the turn of the century (Liepmann 1908), which suggests that there is substantial nonlinguistic overlap in the organization of such movements in hearing persons, who of course do not use hand movements as elements of language. From the authors' point of view, it appears important to demonstrate that the signing defects in their patients with lefthemisphere damage are not attributable to non-language motor programming defects, or apraxia. Unfortunately, the lack of neuropsychological sophistication apparent on this topic is a serious hindrance to its discussion. (The authors erroneously label an example of ideational apraxia as ideomotor apraxia.) Moreover, apraxia is often referred to as though it were any kind of motor disorder, whereas an accepted part of the definition of apraxia is that it is not explicable on the basis of weakness or lack of motility. The authors repeatedly stress...