The Role o f the Auditory Environment in the Development of Speech Production Abilities During Infancy

The role of the auditory environment in prelinguistic speech development has been controversial since at least 1958 when Brown first proposed the "babbling drift hypothesis " (5). The hypothesis that babble progressively approximates the characteristics of the ambient language has been studied primarily by comparing the characteristics of babble with the presumed characteristics of the adult speech produced in the child's environment, with particular emphasis on sounds which are excluded in the adult language, and sounds which are exclusive to the adult language (in comparison with a second language, usually English). Thus far the results have been somewhat contradictory. Locke (5) reviewed studies covering 15 different language environments, and concluded with confidence that the auditory environment does not influence speech production until the age of 18 months. Other studies strongly suggest that the auditor