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.

Expressing Left-Right relations is challenging for speaking-children. Yet, this challenge was absent for signing-children, possibly due to iconicity in the visual-spatial modality of expression. We investigate whether there is also a modality advantage when speaking-children’s co-speech gestures are considered. Eight-year-old child and adult hearing monolingual Turkish speakers and deaf signers of Turkish-Sign-Language described pictures of objects in various spatial relations. Descriptions were coded for informativeness in speech, sign, and speech-gesture combinations for encoding Left-Right relations. The use of co-speech gestures increased the informativeness of speakers’ spatial expressions compared to speech-only. This pattern was more prominent for children than adults. However, signing-adults and children were more informative than child and adult speakers even when co-speech gestures were considered. Thus, both speaking- and signing-children benefit from iconic expressions in visual modality. Finally, in each modality, children were less informative than adults, pointing to the challenge of this spatial domain in development.

Every day people see, describe, and remember motion events. However, the relation between multimodal encoding of motion events in speech and gesture, and memory is not yet fully understood. Moreover, whether language typology modulates this relation remains to be tested. This study investigates whether the type of motion event information (path or manner) mentioned in speech and gesture predicts which information is remembered and whether this varies across speakers of typologically different languages. Dutch- and Turkish-speakers watched and described motion events and completed a surprise recognition memory task. For both Dutch- and Turkish-speakers, manner memory was at chance level. Participants who mentioned path in speech during encoding were more accurate at detecting changes to the path in the memory task. The relation between mentioning path in speech and path memory did not vary cross-linguistically. Finally, the co-speech gesture did not predict memory above mentioning path in speech. These findings suggest that how speakers describe a motion event in speech is more important than the typology of the speakers’ native language in predicting motion event memory. The motion event videos are available for download for future research at https://osf.io/p8cas/.

Previous work indicates that 1) adults with native sign language experience produce more manual co-speech gestures than monolingual non-signers, and 2) one year of ASL instruction increases gesture production in adults, but not enough to differentiate them from non-signers. To elucidate these effects, we asked early ASL–English bilinguals, fluent late second language (L2) signers (≥ 10 years of experience signing), and monolingual non-signers to retell a story depicted in cartoon clips to a monolingual partner. Early and L2 signers produced manual gestures at higher rates compared to non-signers, particularly iconic gestures, and used a greater variety of handshapes. These results indicate susceptibility of the co-speech gesture system to modification by extensive sign language experience, regardless of the age of acquisition. L2 signers produced more ASL signs and more handshape varieties than early signers, suggesting less separation between the ASL lexicon and the co-speech gesture system for L2 signers.

When do the gestures do and do not follow the patterns of the language one speaks? We examined this question by studying 10 Turkish-English bilingual adults (Turkish as L1) in comparison to 10 monolingual English and 10 monolingual Turkish adults as they described motion events either in speech with gesture (co-speech gesture) or only in gesture without speech (silent gesture). All speakers – monolingual and bilingual – showed cross-linguistic differences in co-speech gesture but not in silent gesture. Moreover, bilinguals followed L1 co-speech gesture patterns even when speaking L2, suggesting that acquisition of native-like gesture patterns does not co-occur with the acquisition of native-like speech patterns in bilinguals.