This paper will begin with a discussion of normal language acquisition by children, and a consideration of the neurolinguistic concomitants of both normal and atypical language development. The major perspective here is a social interactionist one: That is, it seems clear now that children acquire language both by virtue of the inherent neuropsychological endowments that are unique to humans, and by the nature of their early interactions with (not just exposure to) older speakers.

After the basic evidence related to acquisition has been presented, the paper will discuss briefly the loss or regression of a first language both in children and adults: Here, the major view is that when some condition such as brain damage causes language regression, the patterns of loss that occur in children are not the same as those that result when adults lose their language under similar conditionschildhood aphasia is qualitatively different from adulthood aphasia. Finally, when adults lose their language through neurological damage, the order of loss is not a mirror image of language acquisition in childhood, although this claim is often made (Jakobson, 1968). The assumption throughout this chapter is that bilingualism and second language development are best understood in the context of our knowledge about monolingual or first language development.

THEORETICAL APPROACHES TO THE STUDY OF LANGUAGE ACQUISITION

Although there is general agreement in the research world about what is entailed in the course of language acquisition by children, there is considerable controversy among theorists about how language development takes place.