Form and Function of Communicative Behaviour Among Persons with Severe Developmental Disabilities

Expanded data bases and theoretical models regarding prelinguistic communication develop ment have important implications for research and clinical practice with severely developmentally disabled individuals. This paper summarises major revisions in our understanding of the early development of communication forms and functions during the prelinguistic period. The authors propose a six-stage account of this developmental process, and a taxonomy of early communicative functions that is applicable to the population of individuals with severe develop mental disabilites. These classification systems were applied in two studies that investigated the relationship between form and function in the Communicative behaviors of 33 nonverbal, severely mentally retarded subjects. ranging in age from 8 to 21 years. The procedures and results of these studies are summarised. Findings from these studies suggest that both overall rate of intentional communication behaviours and diversity of communication functions covary with the symbolic level of these subjects' communication signal forms. The clinical implications of these results, and of the overall revisions in our knowledge base about prelinguistic communication forms and functions, are discussed. These implications include expanded targets and procedures for assessment of severely developmentally disabled clients; as well as major revisions in our clinical treatment contexts and procedures for these clients.