Developmental language disorders: cognitive processes, semantics, pragmatics, phonology, and syntax.

Five areas of research concerned with language acquisition--cognitive processes, semantics, pragmatics, phonology, and syntax--are reviewed in terms of their contribution to understanding language disorders. Two views of cognitive processes are discussed. One of these, emphasizing cognitive mechanisms such as short-term memory, is seen as providing possible explanations for some types of language deficits. The other, a concern with conceptual knowledge, is subjected to a critical analysis questioning how complete an explanation it is able to offer for some aspects of language acquisition. Problems of definition are also discussed when semantic aspects of language are considered. Problems in the pragmatic component of language are seen as providing an explanation for particular aspects of language disorder in some autistic children. The importance of focusing on phonology as a central grammatical process is discussed and linked to dyslexia and to spelling disorders. Finally, it is argued that the acquisition of syntactic structure is not yet understood. Impairments such as a hierarchical planning order deficit may affect syntactic ability and lead to disordered language, as found in some types of developmentally aphasic children. It is concluded that it is important to study all five areas of the title, and their interrelationships, if various language disorders are to be adequately understood.