Developmental changes in gesture forms, functions and meanings in the first three years of life

Co-speech gestures enhance word meanings, while their pragmatic properties support narrative performance. Understanding their development is crucial to tracing the emergence of meaning in communication and language. Existing research has focused on deictic gestures and their predictive role in language acquisition, yet the development of iconic, conventional, and non-referential gestures remains understudied. We longitudinally examined gesture repertoire and use in six infants aged 12 to 36 months) using an ethological framework adapted from nonhuman primate research. Across 3,627 gesture tokens, deictic gestures dominated both repertoire and usage frequency, while non-referential gestures declined with age. Deictic and non-referential repertoires were comparatively larger, but iconic gestures increased developmentally. From 18-months, novel semantic (descriptions of object attributes, abstract concepts, and shared information) and pragmatic (asking questions) functions emerged through diverse gesture forms; iconic gestures significantly drive meaning expansion. These results document the gradual emergence of gesture functions and meanings in early communication.