Preverbal infants can engage in

with adults. Adults who observe and respond positively within appropriate timing to the infants’ protoconversations while playing encourage them to communicate willingly. Evidence shows that caregivers' speech to babbling infants provides crucial, real-time guidance to the development of their prelinguistic vocalizations.

In an experiment with 60 nine and a half month-old infants, mothers of the infants were instructed to provide models of vocal production timed to be either contingent or noncontingent on their infants' babbling. Infants given contingent (immediate response to babbling) feedback rapidly restructured their babbling, incorporating phonological patterns from caregivers' speech. However, infants given noncontingent (non-immediate) feedback did not, showing that preverbal infants learned new vocal forms by discovering phonological (sound structure) patterns in their mothers' contingent speech and then generalising from these patterns to create more sounds to communicate.