A cross-linguistic study of the effect of early experience on vocal development

Children exhibit substantial vocal development in their first years of life, laying the foundation for later language. This paper asks how key aspects of their linguistic experience relates to one aspect of this development. We focus on three factors that have been argued to influence vocal development: the amount of language input that infants hear, the likelihood of hearing adult vocalizations temporally contingent on infants’ productions, and the amount of time children spend vocalizing. We test the relationship between these three factors and one measure of vocal development (canonical proportion, which estimates the prevalence of transitions between consonants and vowels in spontaneous speech) using long-form recordings in a large sample. The children in the dataset (N = 204, aged 2-18 months) were growing up in diverse cross-cultural urban and rural settings, and were learning one or more typologically-varied languages. With this well-powered, diverse sample, we predict that we will see significant positive relationships between each of the factors explored and this measure of vocal development.