NEUROLINGUISTIC ASPECTS OF LANGUAGE ACQUISITION AND BILINGUALISM

Two general questions are addressed in this paper: (a) Have the parameters of brain maturation contributed to our understanding of either monolingual or bilingual language acquisition? and (b) What do the current data on language representation in the brains of adult monolingual and multilingual speakers suggest by way of a neurolinguistic model? To anticipate the gist of this paper, the outlook is somewhat on the bleak side. First, brain maturation does not appear to be a monolithic event to which the milestones of language acquisition can be correlated easily. Second, nonlocalizationist models of brain-language relationships simply are a silly way to do neurolinguistic science; unfortunately, most current localizationist models do not do an adequate job of accounting for the known facts. On the other hand, the fact that we have at least this much understanding of neurolinguistic aspects of language acquisition and bilingualism is rather direct testimony to the progress that has been made in the field. In 1967 Lenneberg assembled an extensive body of research and ideas and proposed a number of now-familiar hypotheses concerning the neurological aspects of 1anguage.l He suggested that the two cerebral hemispheres initially are equipotential for language, that cerebral lateraliiation gradually develops until it is complete at puberty, and that there is a critical period for language acquisition from two years of age to puberty that is limited and determined by the maturation of the brain. The specific concomitants of physical maturation of the brain to which he referred were changes in cellbody volume, in neurodensity, and in some of the neurochemical components of the brain. Lenneberg’s analysis of these criteria led him to postulate a rapid rate of growth until age two, followed by a slow rise, asymptoting at puberty. His view of brain maturation as a single process was quite explicit: “Since the various aspects of cerebral maturation are so highly correlated we may think of maturation of the brain as a relatively unitary phenomenon.” The hypotheses of equipotentiality, the developnient of lateralization or dominance (currently being discussed in terms of both specialization and