Vocalisations are coupled with movement of all limbs throughout infancy

Early speech development involves learning complex motor actions under constantly changing body proportions and biomechanics. However, the motor underpinnings of infant vocal production are largely unknown. The key question is whether vocal production (a complex motor action) is related to limb movements at the early stages of learning to speak. We tracked the development of coupling between limb movements and vocalisations in infants at 4, 6, 9 and 12 months of age. Limb movements were tightly coupled with vocalisation onsets at all time points across infancy. The initiation of speech-like vocalisations in early life is accompanied by movements of legs and arms. These findings suggest that the coupling of limb movements with vocalisation could be a potential mechanism supporting vocal production in early infancy, as well as a likely precursor to the emergence of gestures.