A recent meta-analytic review published in Psychological Bulletin confirms that adults exaggerate vowel sounds when speaking to infants. This phenomenon, known as vowel hyperarticulation in infant-directed speech (IDS), was examined by an international team of scientists.
The research, led by the International Research Center for Neurointelligence (WPI-IRCN) at The University of Tokyo, along with collaborators from the University of Amsterdam, PSL University, and Aarhus University, analyzed 20 studies specifically investigating vowel hyperarticulation in IDS. They also included a broader analysis of 35 studies using various research techniques.
The meta-analysis revealed that caregivers tend to hyperarticulate vowels like /a/, /i/, and /u/ when interacting with infants across at least ten languages. This exaggerated vowel space, visualized as larger triangles in the acoustic plane, suggests clearer, more distinct vowel sounds are produced.
This exaggeration is believed to facilitate language learning during a sensitive developmental window. By expanding the vowel space, caregivers may provide infants with amplified acoustic cues. This helps highlight the boundaries between different vowel categories, making speech perception and word segmentation easier.
The authors note that methodological diversity among the analyzed studies affects result comparability. They call for larger, more rigorous studies to explore cross-linguistic and cross-cultural variability. The study's lead author, Dr. Irena Lovčević, highlights the broader implications for understanding infant language development.
The research underscores the dynamic process of human speech acquisition, combining neuroscience, linguistics, and cognitive science. The study was supported by grants including Japan's MEXT World Premier International Research Center Initiative and JSPS KAKENHI. Future research will refine acoustic measurement and integrate neurodevelopmental perspectives.
This study confirms that exaggerated vowel articulation is a feature of baby talk and a potential cornerstone in early language learning. The team hopes to unravel the "big puzzle" of effortless infant language acquisition, from the acoustic properties of caregiver speech to the underlying neural computations.