Developmental Language Disorders: From Phenotypes to Etiologies

Historically, language has often been conceived as something “out there, ” in the outside world, rather than a system of mind or brain (Sampson, 1980). For a relatively recent example, Saussure (1915/1972) defined “langue” as a socially constituted system of signs. When B. F. Skinner (1957) adapted the behaviorist approach to the study of language, he described the rules of language in terms of reinforcement and conditioning (i.e., as fully determined by external parameters of stimulus and response). It was Chomsky's (1959) groundbreaking criticism of Skinner's book that launched the study of language as a mental system. Chomsky's early work on syntax as a mental system of quasi-mathematical rules (Chomsky, 1957, 1965) was an integral part of the newly developing “cognitive sciences” (Gardner, 1987). Later, Chomsky went a step further and reunited linguistics with biology. According to his views, language was a “mental organ” that would mature based on biological necessity (rather than environmental contingency) in the course of child development, in similar ways as a heart or lung would mature (Chomsky, 1980). At the time, these views were radical compared with competing behaviorist and Piagetian views that granted experience an important role in language development (Piattelli-Palmarini, 1980). Chomsky's views were also radical with respect to the role they allotted genetic information. Chomsky believed that “universal grammar, ” a set of abstract principles determining

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