Zoe Hommerich & Molly Flaherty, PhD, Davidson College

Studies of silent gestures – meaningful hand movements that are not accompanied by speech –examine how hearing, non-signer individuals spontaneously use their hands, and not their voices to communicate. Since silent gestures are not part of a natural language, their study provides us with unique insight into universal human preferences for grammatical properties and the emergence of new language systems without having to battle the threat of native language bias. In the literature, silent gesture production studies often show participants’ preference for using target gestures aimed at communicating a noun earlier in the utterance, and target gestures communicating verbs in final position. This study aimed to investigate how adults interpret silent gesture utterances that are ambiguous in terms of whether the target gesture referred to a noun or a verb and to see if we observe the same biases in this comprehension task as has been observed in production. Through an online survey, a total of 499 hearing, non-signer participants completed a two-alternative forced-choice task, in which they were presented with two video stimuli showing 2-gesture silent gesture strings that were either in “point + target gesture” (point initial, PI) or “target gesture + point” (point final, PF) gesture order. Participants were then asked to match one video to nominal, and the other to verbal English meaning. A comprehension check and language question were included to ensure quality of participant responses, and exclude participants based on exclusion criteria. Contrary to the preregistered hypothesis, the results showed a significant preference towards interpreting ambiguous gestures in utterance initial position as verbs and those in utterance final position as nouns (62.3%, p < .001). This preference was observed regardless of reported spoken languages. An exploratory analysis that excluded participants who reported difficulty making a clear distinction between the two stimulus videos revealed that the preference for matching PI gesture order with English nominal meaning remained stable and significant. These findings suggest that the noun-verb ordering distinction during the comprehension of silent gesture utterances may be governed by different mechanisms than those during production. Overall, this study highlights the importance of investigating production and comprehension of silent gestures separately, to obtain a comprehensive understanding of language emergence and universal preferences for language creation. A follow-up study replicating this design is recommended.