CONCEPT
The Poverty of the Stimulus
Noam Chomsky’s foundational empirical argument that children acquire grammatical competence far richer than the available evidence could justify—proving that the structure of human language cannot be learned from data alone, and that the human language faculty must be partly given in advance by a dedicated biological endowment.
The poverty of the stimulus is the most important idea Chomsky gave to the science of mind, and the concept on which the entire debate about AI and language turns. It names a specific and embarrassing gap: the sentences a child hears are finite, fragmentary, and frequently ungrammatical, yet the child extracts from this impoverished input an infinite, rule-governed linguistic system—without explicit instruction, without systematic correction, within a narrow developmental window, and with the same precise result as every other child of the same language. The convergence of every child on the same narrow target, from impoverished input, is inexplicable on the hypothesis that language is learned from data by general mechanisms of association and pattern-matching. The grammar is not in the data; the grammar must be partly given in advance, by a dedicated faculty present at birth and common to the species.
Chomsky’s 1959