TY - JOUR
T1 - Infant-directed speech facilitates word learning through attentional mechanisms
T2 - An fNIRS study of toddlers
AU - Zhou, Xin
AU - Wang, Luchang
AU - Hong, Xuancu
AU - Wong, Patrick C.M.
N1 - Funding Information:
We sincerely thank all the parents and toddlers for participating in this research. We also acknowledge support from The Chinese University of Hong Kong, The Chinese University of Hong Kong—Utrecht University Joint Centre for Language, Mind and Brain, Nanyang Technological University of Singapore, and Western Sydney University Joint Laboratory for Infant Research. This research was supported by the Research Grants Council of Hong Kong (C4055‐19GF) and the Chinese University of Hong Kong, a grant from National Institute of Health (R01DC019387), and the John Simon Guggenheim Memorial Foundation for a fellowship awarded to PCMW.
Publisher Copyright:
© 2023 The Authors. Developmental Science published by John Wiley & Sons Ltd.
PY - 2023/6/15
Y1 - 2023/6/15
N2 - The speech register that adults especially caregivers use when interacting with infants and toddlers, that is, infant-directed speech (IDS) or baby talk, has been reported to facilitate language development throughout the early years. However, the neural mechanisms as well as why IDS results in such a developmental faciliatory effect remain to be investigated. The current study uses functional near-infrared spectroscopy (fNIRS) to evaluate two alternative hypotheses of such a facilitative effect, that IDS serves to enhance linguistic contrastiveness or to attract the child's attention. Behavioral and fNIRS data were acquired from twenty-seven Cantonese-learning toddlers 15–20 months of age when their parents spoke to them in either an IDS or adult-directed speech (ADS) register in a naturalistic task in which the child learned four disyllabic pseudowords. fNIRS results showed significantly greater neural responses to IDS than ADS register in the left dorsolateral prefrontal cortex (L-dlPFC), but opposite response patterns in the bilateral inferior frontal gyrus (IFG). The differences in fNIRS responses to IDS and to ADS in the L-dlPFC and the left parietal cortex (L-PC) showed significantly positive correlations with the differences in the behavioral word-learning performance of toddlers. The same fNIRS measures in the L-dlPFC and right PC (R-PC) of toddlers were significantly correlated with pitch range differences of parents between the two speech conditions. Together, our results suggest that the dynamic prosody in IDS increased toddlers’ attention through greater involvement of the left frontoparietal network that facilitated word learning, compared to ADS. Research Highlights: This study for the first time examined the neural mechanisms of how infant-directed speech (IDS) facilitates word learning in toddlers. Using fNIRS, we identified the cortical regions that were directly involved in IDS processing. Our results suggest that IDS facilitates word learning by engaging a right-lateralized prosody processing and top-down attentional mechanisms in the left frontoparietal networks. The language network including the inferior frontal gyrus and temporal cortex was not directly involved in IDS processing to support word learning.
AB - The speech register that adults especially caregivers use when interacting with infants and toddlers, that is, infant-directed speech (IDS) or baby talk, has been reported to facilitate language development throughout the early years. However, the neural mechanisms as well as why IDS results in such a developmental faciliatory effect remain to be investigated. The current study uses functional near-infrared spectroscopy (fNIRS) to evaluate two alternative hypotheses of such a facilitative effect, that IDS serves to enhance linguistic contrastiveness or to attract the child's attention. Behavioral and fNIRS data were acquired from twenty-seven Cantonese-learning toddlers 15–20 months of age when their parents spoke to them in either an IDS or adult-directed speech (ADS) register in a naturalistic task in which the child learned four disyllabic pseudowords. fNIRS results showed significantly greater neural responses to IDS than ADS register in the left dorsolateral prefrontal cortex (L-dlPFC), but opposite response patterns in the bilateral inferior frontal gyrus (IFG). The differences in fNIRS responses to IDS and to ADS in the L-dlPFC and the left parietal cortex (L-PC) showed significantly positive correlations with the differences in the behavioral word-learning performance of toddlers. The same fNIRS measures in the L-dlPFC and right PC (R-PC) of toddlers were significantly correlated with pitch range differences of parents between the two speech conditions. Together, our results suggest that the dynamic prosody in IDS increased toddlers’ attention through greater involvement of the left frontoparietal network that facilitated word learning, compared to ADS. Research Highlights: This study for the first time examined the neural mechanisms of how infant-directed speech (IDS) facilitates word learning in toddlers. Using fNIRS, we identified the cortical regions that were directly involved in IDS processing. Our results suggest that IDS facilitates word learning by engaging a right-lateralized prosody processing and top-down attentional mechanisms in the left frontoparietal networks. The language network including the inferior frontal gyrus and temporal cortex was not directly involved in IDS processing to support word learning.
KW - functional near-infrared spectroscopy
KW - infant-directed speech
KW - modified intermodal preferential paradigm
KW - toddler
KW - word learning
UR - http://www.scopus.com/inward/record.url?scp=85162068453&partnerID=8YFLogxK
U2 - 10.1111/desc.13424
DO - 10.1111/desc.13424
M3 - Article
C2 - 37322865
AN - SCOPUS:85162068453
SN - 1363-755X
VL - 27
SP - e13424
JO - Developmental Science
JF - Developmental Science
IS - 1
M1 - e13424
ER -