Forms and Functions of Gestures in Preverbal 12- to 15-Months Old Infants.

Speech and co-speech gestures always go hand in hand. Whether we find the precursors of these co-speech gestures in infants before they master their native language still remains an open question. Except for deictic gestures, there is little agreement on the existence of iconic, non-referential and conventional gestures before children start producing their first words. Here, we bridge this knowledge gap by leveraging an ethological method already established for describing speech independent gestures in nonhuman primates, to analyze the spontaneous gestures produced by infants when interacting with their caregivers. We manually annotated video recordings of infant-caregiver interactions (26 h) from the CHILDES platform, to describe the gesture forms, types and functions in six infants from 12 to 15 months of age. We describe 62 gesture forms in the preverbal repertoire. These were categorized into deictic, iconic, non-referential and conventional gesture types, similar to co-speech gesture types. We also find that the type-function relation of preverbal gestures map similarly to type-meaning relation of co-speech gestures. Taken together, our results illustrate linguistic properties of infant gestures in the absence of speech, suggesting them to be precursors of co-speech gestures.