When gesture-speech combinations do and do not index linguistic change

Abstract

At the one-word stage children use gesture to supplement their speech ('eat'+point at cookie), and the onset of such supplementary gesture-speech combinations predicts the onset of two-word speech ('eat cookie'). Gesture thus signals a child's readiness to produce two-word constructions. The question we ask here is what happens when the child begins to flesh out these early skeletal two-word constructions with additional arguments. One possibility is that gesture continues to be a forerunner of linguistic change as children flesh out their skeletal constructions by adding arguments. Alternatively, after serving as an opening wedge into language, gesture could cease its role as a forerunner of linguistic change. Our analysis of 40 children--from 14 to 34 months--showed that children relied on gesture to produce the first instance of a variety of constructions. However, once each construction was established in their repertoire, the children did not use gesture to flesh out the construction. Gesture thus acts as a harbinger of linguistic steps only when those steps involve new constructions, not when the steps merely flesh out existing constructions.

Figure 1

Mean number of gesture-speech combinations produced by children at 14, 18, 22, 26, 30 and 34 months of age categorized according to type (error bars represent standard errors)

Figure 2

Number of children who produced utterances with two or more arguments (panel A), utterances with a predicate and at least one argument (panel B), or utterances with two predicates (panel C) in speech alone (dashed lines) or in a gesture-speech combination (solid lines)

Figure 3

Mean number of gesture-speech combinations with two or more arguments (panel A), combinations with a predicate and at least one argument (panel B), or combinations with two predicates (panel C) produced by children (solid lines) or their parents (dashed lines) (error bars represent standard errors).

Figure 4

Number of children who produced utterances with two arguments (panel A) or three arguments (panel B) in speech alone (dashed lines) or in a gesture-speech combination (solid lines)

Figure 5

Number of children who produced utterances with a predicate and one argument (panel A), utterances with a predicate and two arguments (panel B), or utterances with a predicate and three arguments (panel C) in speech alone (dashed lines) or in a gesture-speech combination (solid lines)

Figure 6

Number of children who produced utterances with two predicates and one or zero argument (panel A), utterances with two predicates and two or more arguments (panel B) in speech alone (dashed lines) or in a gesture-speech combination (solid lines)