The nature of infant vocal behaviour development between 8 and 17 months and its role in communication with mother

ABSTRACT Objective The tendency to vocalize toward objects is ubiquitous among young infants. However, little is known about the range of this tendency and its contribution to language development. Therefore, this longitudinal study objective was to explore the role of three forms of vocal behavior (vocalization, babbling, and speech) directed toward objects in communication with caregiver. Method To measure the spontaneous usage of vocal behaviors, 14 infants observed for 9 months and between the ages of 8 and 17 months, in their natural home environments once a month for a one-hour session with their mothers sitting nearby. Results A total of 1,961 vignettes were gathered and analyzed. It was found that, among the three forms of vocal behavior, object-directed vocalization was the most extensive at the age of 8 months. Repeated measures analysis showed that the frequency of each type of vocal output directed toward an object was associated with a rate of similar vocal output that was later directed toward the mother. Conclusions The discussion explains the change in vocal behavior rates and discusses the role of auditory feedback and contribution of the engagement with objects to explain the role of object-directed vocal outputs in later communication with others. KEY POINTS What is already known about this topic (1) Between the ages of 8 and 17 months, infants produce three types of vocal outputs: vocalisation (consonants and consonant-vowel repetition), babbling (baba, dada) and speech (one-word utterances). (2) Infants may direct their vocal outputs towards an object or a caregiver. (3) Vocal outputs play a key role in language development through auditory feedback when infants vocalise when alone and through caregivers’ verbal responses. What this topic adds (1) Vocalisation towards objects was the predominant tendency until infants approached their first birthday. (2) There is an association between the rate of object-directed vocalisation and later mother-directed vocalisation. (3) Object-directed vocalisation is an opportunity for rehearsing and mastering lingual forms that befit language development.