Early Emergence and Development of Protophones in the First Year of Life


Objectives: Speech-like vocalizations (i.e., protophones) are precursors to speech. Infants produce various types of protophones (e.g., squeals, vocants and growls), practicing phonatory control before mastering articulation. In order to better understand infant vocal development, it is important to systematically investigate production of protophones from the beginning of life. The purposes of this study were (1) to investigate early emergence of protophones, (2) to measure volubility for both cry and protophones across the first year of life, (3) to explore effects of age and types of vocalizations, and (4) to examine protophone volubility in circumstances where the caregiver did not speak to or in the vicinity of the infant. Methods: 16 typically developing Korean-learning infants participated in all-day LENA (Language Environment Analysis) recordings in their homes as part of a longitudinal study. We categorized infant protophones as either squeals, vocants, growls, or cries based on auditory/acoustic criteria. We calculated average numbers of each type of vocalization and average vocalizations per minute. Generalized Estimating Equations (GEE), t-test, and ANOVA were conducted to address the research questions. Results: Results showed that even in the first month of life, infants do not merely cry, but instead predominantly produce protophones. Infants also endogenously produced protophones from the beginning of life in the absence of caregiver language input. Conclusion: This study suggests that even in the first month protophones begin to occur, and may form a foundation upon which vocal category development and vocal interaction can proceed rapidly.

Publication Title

Communication Sciences and Disorders