Role of mothers' expansions in stimulating children's language production.

Mothers' expansions were examined for their role in structuring conversational contributions and facilitating spontaneous imitations and productions of two-term semantic relations not previously used by their children. The subjects were four 2-year-old boys in late Stage 1 of linguistic development and their mothers. The investigation consisted of two studies. Study 1, a descriptive analysis of mother-child conversation, showed a contingent relationship between mothers' expansions and their children's use of spontaneous imitations. Study 2, an experimental procedure using a multiple baseline treatment design, showed that an increase in the mothers' expansions was systematically related to an increase in the children's initial spontaneous imitations of two-term semantic relations. Results also indicated that following the increase in spontaneous imitations, spontaneous productions of the two-term relations increased and were maintained, whereas spontaneous imitations subsequently decreased.