The effects of incidental teaching on vocabulary acquisition by young children.

The effects on vocabulary acquisition of child-initiated versus adult-initiated instances of adult labeling were studied. 16 monolingual, English-speaking preschool children were exposed to a Spanish-speaking adult. In order to have access to toys placed out of their reach, children had to request the toys in Spanish. For the experimental group, adult labeling occurred when the children expressed interest in the toy. Control group children were yoked temporally to experimental group children for the purpose of adult labeling. Thus, adult labeling for the control group was randomly related to the children's expressions of interest. Although both groups of children learned some Spanish words, children in the experimental group produced significantly more Spanish words during the training sessions and showed superior performance on posttraining tests of Spanish production. Levels of comprehension of the Spanish words were equivalent for both groups. Results are interpreted in the context of the literature on "incidental teaching" and are viewed as demonstrating the critical role in language acquisition of the timing of exposure to language models.