The development of speech and language

Infants learn language with remarkable speed. By the end of the second year they speak in sentences, sounding distinctly like a speaker of the "mother tongue." How does one individual acquire a specific language? Is it appropriate to call it "learning" in the traditional sense? Historically, two dramatically opposed views formed the cornerstones of the debate on language. According to one view, a universal grammar and phonology are innately provided and input serves to trigger this information. In the other view, no innate knowledge is provided and language is acquired through a process of feedback and reinforcement. Both theories are based on assumptions about the nature of language input to the child and the nature of the developmental change induced by input. New data reviewed here, showing the effects of early language experience on infants, suggest a theoretical revision. By one year of age, prior to the time infants begin to master higher levels of language, infants' perceptual and perceptual-motor systems have been altered by linguistic experience. Phonetic perception has changed dramatically to conform to the native-language pattern, and language-specific speech production has emerged. According to the model described here, this developmental change is caused by a complex "mapping" of linguistic input. This account is different in two respects from traditional views: (1) language input is not conceived of as triggering innately provided options, and (2) the kind of developmental change that occurs does not involve traditional Skinnerian learning, in which change is brought about through feedback and reinforcement. The consequences of this are described in st developmental theory at the phonetic level that holds promise for higher levels of language.