What the development of gesture with and without speech can tell us about the effect of language on thought

Adults display cross-linguistic variability in their speech in how they package and order semantic elements of a motion event. These differences can also be found in speakers' co-speech gestures (gesturing with speech), but not in their silent gestures (gesturing without speech). Here, we examine when in development children show the differences between co-speech gesture and silent gesture found in adults. We studied speech and gestures produced by 100 children learning English or Turkish (n = 50/language) - equally divided into 5 age-groups: 3-4, 5-6, 7-8, 9-10, and 11-12 years. Children were asked to describe three-dimensional spatial event scenes (e.g., a figure crawling across carpet) first with speech and then without speech using their hands. We focused on physical motion events that elicit, in adults, cross-linguistic differences in co-speech gesture and cross-linguistic similarities in silent gesture. We found the adult pattern even in the youngest children: (1) Language shaped co-speech gesture beginning at age 3 years, showing an early effect of language on thinking for speaking (as measured by gestures that occur during the speech act). (2) Language did not affect silent gesture at any age, highlighting early limits on the effects language has on thinking and revealing a language of gesture that shows similarities across languages.