Evidence map›Paper›PMID 42095512›Full record

ArticleDevelopmental science2026

Hemodynamic Responses to Word Forms in Japanese Infant-Directed Vocabulary in 5- and 9-Month-Old Infants: Early Sensitivity to Prosodic Structure and Emergence of Prosodic Representations.

Yoritaka Akimoto, Miki Takahasi, Naoto Yamane, Rachel Ka-Ying Tsui, Akiko Hayashi, Reiko Mazuka

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Article in Developmental science, 2026. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Not yet cited in PubMed.

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5 · Who and what money

Authors and funding

6 authors.

Yoritaka AkimotoInformation & Management Systems Engineering, Nagaoka University of Technology, Niigata, Japan.ORCID https://orcid.org/0000-0002-0233-0180
Miki TakahasiRIKEN Center for Brain Science, Wako, Japan.ORCID https://orcid.org/0009-0005-1281-9982
Naoto YamaneRIKEN Center for Brain Science, Wako, Japan.
Rachel Ka-Ying TsuiRIKEN Center for Brain Science, Wako, Japan.ORCID https://orcid.org/0000-0002-0152-3132
Akiko HayashiCenter for the Research and Support of Educational Practice, Tokyo Gakugei University, Koganei, Japan.
Reiko MazukaRIKEN Center for Brain Science, Wako, Japan.ORCID https://orcid.org/0000-0001-7862-7768

Funding

Japan Society for the Promotion of Science (JSPS) KAKENHI 16H06319Japan Society for the Promotion of Science (JSPS) KAKENHI 16K12451Japan Society for the Promotion of Science (JSPS) KAKENHI 20H05617Japan Society for the Promotion of Science (JSPS) Program for Forming Japan's Peak Research Universities (J-PEAKS) JPJS00420240017RIKEN Pioneering Research Project (Neurophysiological Mechanisms Toward Input-Driven Language Development)
6 · The paper itself

Abstract

The prosodic characteristics of a native language greatly influence early language acquisition. Yet, Japanese mothers are known to use a specific prosodic structure in infant-directed vocabulary (IDV)-specifically, three-mora, two-syllable words with a heavy-light pattern-which, crucially, differs from the standard prosodic rhythm of adult vocabulary. This study used near-infrared spectroscopy to examine hemodynamic responses to the Japanese IDV form in 5-month-old (n = 31) and 9-month-old (n = 34) Japanese infants, targeting the period before and during the emergence of this preference. The results revealed that oxygenated hemoglobin was greater for the IDV form than for the non-IDV form in the left superior temporal gyrus (STG) for both age groups, consistent with the advantage of the IDV form observed in previous behavioral studies. Furthermore, this effect was localized to the left middle and left posterior STG in 5- and 9-month-old infants, respectively, highlighting early sensitivity to its prosodic structure followed by the emergence of phonological representation. This cortical shift, along with an observed trend toward adult-like patterns, may suggest a broader transition from perceptually accessible IDV structures to the more diverse patterns of standard adult vocabulary. Although 5-month-old infants who have not yet exhibited a preference for the IDV form may not have developed specific phonological representations, their brains' ability to process its prosodic pattern could serve as a foundation for subsequent learning. These findings demonstrate that the specific structure of Japanese IDV acts as a foundational scaffold, guiding the transition from initial prosodic tuning to mature word-level processing. SUMMARY: Early sensitivity to prosodic structure was observed in 5-month-old Japanese infants. Emerging phonological representation was observed in 9-month-old Japanese infants. Japanese infant-directed vocabulary form serves as a prosodic template.

Indexed as

HemodynamicsLanguage DevelopmentSpeech PerceptionVocabularyEast Asian PeopleFemaleHumansInfantJapanLanguageMaleSpectroscopy, Near-InfraredTemporal Lobedevelopmental changefNIRSinfant‐directed vocabularyJapaneselanguage acquisitionprosodic structure

Identifiers

PMID42095512
PMCPMC13151418

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