Vocal interactions at the dawn of communication: The emergence of mutuality and complementarity in mother-infant interaction

Continuous interaction of mother and infant in the first weeks and months of an infant's life entrains the infant on many crucial aspects of how to do things together. Contingencies of gaze, vocalizations, and other movements are slowly routinized; this scaffolds directing of attention to each other and the world and gives to such multimodal interactions meaning. It is within these continuous interactions with caregivers that language emerges, starting from the first non-reflexive vocalizations that infants produce. The response that caregivers promptly give to these vocalizations informs infants of their relevance and helps shape them. We explored this systematicity by observing the coupling of infants' and mothers' vocalizations in unconstrained interactions longitudinally. While at three months, mothers seem to answer consistently to any speech related vocalization within the first two seconds, this pattern fades away at six and eight months. What remains stable across age is a structure in which overlapping vocalizations are rare and give way to a sequential pattern of vocal reciprocity — an embryonic turn-taking behavior. Discussion relates this finding to early coordination in other modalities in an attempt to sketch a more holistic account of emerging co-action.