A Systematic Review and Bayesian Meta-Analysis of the Acoustic Features of Infant-Directed Speech

Christopher Cox, Christina Bergmann, Emma Fowler, Tamar Keren-Portnoy, Andreas Roepstorff, Gregory A. Bryant, Riccardo Fusaroli

Research output: Contribution to journalArticlepeer-review


When speaking to infants, adults often produce speech that differs systematically from that directed to other adults. To quantify the acoustic properties of this speech style across a wide variety of languages and cultures, we extracted results from empirical studies on the acoustic features of infant-directed speech. We analysed data from 88 unique studies (734 effect sizes) on the following five acoustic parameters that have been systematically examined in the literature: fundamental frequency (f0), f0 variability, vowel space area, articulation rate and vowel duration. Moderator analyses were conducted in hierarchical Bayesian robust regression models to examine how these features change with infant age and differ across languages, experimental tasks and recording environments. The moderator analyses indicated that f0, articulation rate and vowel duration became more similar to adult-directed speech over time, whereas f0 variability and vowel space area exhibited stability throughout development. These results point the way for future research to disentangle different accounts of the functions and learnability of infant-directed speech by conducting theory-driven comparisons among different languages and using computational models to formulate testable predictions.
Original languageEnglish
Pages (from-to)114–133
Number of pages20
JournalNature Human Behaviour
Early online date3 Oct 2022
Publication statusPublished - 1 Jan 2023

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