"more" had to be extended beyond a particular routine such as asking for more cookies. The overall goal was to determine when gestures were, in Snyder, Bates, and Brethertons (1981) terms, "context-flexible." The application of the rules described above was initially done by one coder. A second coder reviewed the interviews for 10% of the subjects. Inter-coder reliability was determined by calculating the number of agreements (i.e., both coders agreed on the interview date during which a specific gesture reached "generalized" status) divided by the number of agreements plus disagreements. Inter-coder reliability was 92%. The three universally acquired symbolic gestures, "byeDiscussionThe results of the present study, particularly the comparisons between the Sign Training group and the Non-intervention Control group, strongly support the hypothesis that symbolic gesturing facilitates the early stages of verbal language development. In a significant proportion of the comparisons between these two groups, infants who augmented their fledgling vocal vocabularies with symbolic gestures outperformed those who did not. The fact that no such advantage was found for the infants in the Verbal Training group provides reassuring evidence that the superior performance of the ST infants was not simply a function of their families being involved in a language-centered intervention program. The explanation seems to lie instead within the gesturing experience itself. Explaining the AdvantageIncreases in infant-directed speech. Among the most well documented factors affecting the rate at which language is acquired is the sheer amount of vocalization directed to the child (Huttenlocher, Haight, Bryk, Seltzer, & Lyons, 1991). One McIntyre7clue, therefore, to why symbolic gesturing is associated with more rapid verbal language development may lie in the way adults tend to respond to an infant who uses a symbolic gesture. As is true of early words as well, t...
