Babbling Drift in Bilingual Infants: A Systematic Review

Purpose: This systematic review synthesizes existing evidence on bilingual babbling, with a focus on the emergence of language-specific effects in infant vocal production and on infants' capacity to differentiate their vocalizations across language contexts. Three linguistic domains are examined: segmental, syllabic, and utterance structure with prosodic acoustics. The validity of the babbling drift hypothesis is also discussed. Method: A total of 219 articles were screened across six databases, of which only seven met the inclusion criteria. In synthesizing findings, priority was given to quantitative studies with controlled methodology and within-subject designs, while single-case studies offered anecdotal support. Results: Evidence of language differentiation was found primarily at the prosodic level. The timing aligns with the babbling drift hypothesis, though most studies examined structural rather than phonetic–acoustic properties. Conclusions: Although evidence of babbling drift was identified, particularly for utterance length, the empirical base remains small and heterogeneous. The review therefore outlines key methodological considerations and best practices to guide future research in this still underdeveloped field. Supplemental Material: https://doi.org/10.23641/asha.33965401