Abstract
We investigated the hypothesis that infants search in an acoustic space for vocalisations that elicit adult utterances and vice versa, inspired by research on animal and human foraging. Infant-worn recorders were used to collect day-long audio recordings, and infant speech-related and adult vocalisation onsets and offsets were automatically identified. We examined vocalisation-to-vocalisation steps, focusing on inter-vocalisation time intervals and distances in an acoustic space defined by mean pitch and mean amplitude, measured from the child’s perspective. Infant inter-vocalisation intervals were shorter immediately following a vocal response from an adult. Adult intervals were shorter following an infant response and adult inter-vocalisation pitch differences were smaller following the receipt of a vocal response from the infant. These findings are consistent with the hypothesis that infants and caregivers are foraging vocally for social input. Increasing infant age was associated with changes in inter-vocalisation step sizes for both infants and adults, and we found associations between response likelihood and acoustic characteristics. Future work is needed to determine the impact of different labelling methods and of automatic labelling errors on the results. The study represents a novel application of foraging theory, demonstrating how infant behaviour and infant-caregiver interaction can be characterised as foraging processes.
Highlights
We investigated the hypothesis that infants search in an acoustic space for vocalisations that elicit adult utterances and vice versa, inspired by research on animal and human foraging
Results from a linear mixed effects model with acoustic step size being predicted by inter-vocalisation interval, controlling for age and infant ID, indicate that step sizes in acoustic space and time are positively correlated for both infants (β = 0.07, p =
We found that correlations between inter-vocalisation intervals and acoustic distance between vocalisations were weak
Summary
We investigated the hypothesis that infants search in an acoustic space for vocalisations that elicit adult utterances and vice versa, inspired by research on animal and human foraging. Adult intervals were shorter following an infant response and adult inter-vocalisation pitch differences were smaller following the receipt of a vocal response from the infant. Infants demonstrate a much wider range of vocalisation types, varying pitch, amplitude, and other phonatory characteristics During this time, they start producing primitive consonant-vowel articulations. By 7 months, infants begin producing well-timed adult-like consonant-vowel alternations This expansion in repertoire lays a foundation for later speech and other vocal communication production[2,6]. Infant vocal learning may be viewed as a process that combines variation and selection, resulting in the evolution of a more adult-like repertoire of sound types This perspective raises the question of how variability serves to explore the space of vocalisations in a way that selects those that are successful in terms of social interaction and communication. The same study found that the adult vocalisations to which infants were exposed exhibited nested temporal clustering, with the degree of nesting being coordinated between infants and adults
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