Toward a Fuller Integration of Respiratory Rhythms Into Research on Infant Vocal and Motor Development.

Rhythm organizes many human motor activities from before birth and continues to shape development throughout infancy. In this review, we examine the role of rhythmic processes in early vocal development, drawing on research from motor control, physiology, speech, and language acquisition. We propose that respiration functions as a crucial core of early rhythmic coordination, linking vocalizations and bodily movements into an integrated system. At present, we have an imprecise understanding of how infant breathing for speech develops during the first year of life. However, respiration, an inherently flexible and adaptive system, may provide a temporal framework within which speech articulation and motor actions become progressively aligned. During canonical babbling, a key milestone in language acquisition, repetitive adult-like syllables emerge from rhythmic motor actions. The advent of this behavior presumably reflects developing coordination among motor, respiratory, and vocal subsystems. This three-way coordination creates the multimodal foundation of language. In this perspective, the respiratory rhythm is fundamental to early vocal development. Along with reviewing past work and its limitations, we suggest directions for future work to better address how the respiratory rhythm subserves developing linguistic and nonlinguistic actions in infant development.