Temporal Coordination in Mother-Infant Vocal Interaction: A Cross-Cultural Comparison.

Temporal coordination of vocal exchanges between mothers and their infants emerges from a developmental process that relies on the ability of communication partners to co-coordinate and predict each other's turns. Consequently, the partners engage in communicative niche construction that forms a foundation for language in human infancy. While robust universals in vocal turn-taking have been found, differences in the timing of maternal and infant vocalizations have also been reported across cultures. In this study, we examine the temporal structure of vocal interactions in 38 mother-infant dyads in the first two years across two cultures-American and Lebanese-by studying observed and randomized distributions of vocalizations, focusing on both gaps and overlaps in naturalistic 10-min vocal interactions. We conducted a series of simulations using Kolmogorov-Smirnov (K-S) tests to examine whether the observed responsivity patterns differed from randomly generated simulations of responsivity patterns in both Arabic and English for mothers responding to infants and for infants responding to mothers. Results revealed that both mothers and infants engaged in conversational alternation, with mothers acting similarly across cultures. By contrast, significant differences were observed in the timing of infant responses to maternal utterances, with the Lebanese infants' tendency to cluster their responses in the first half-second after the offset of the Lebanese mothers' utterances to a greater extent than their American counterparts. We speculate that the results may be due to potential phonotactic differences between Arabic and English and/or to differing child-rearing practices across Lebanese and American cultures. The findings may have implications for early identification of developmental disorders such as autism spectrum disorders within and across cultures.

Cross-Cultural Register Differences in Infant-Directed Speech: An Initial Study.

Infant-directed speech (IDS) provides an environment that appears to play a significant role in the origins of language in the human infant. Differences have been reported in the use of IDS across cultures, suggesting different styles of infant language-learning. Importantly, both cross-cultural and intra-cultural research suggest there may be a positive relationship between the use of IDS and rates of language development, underscoring the need to investigate cultural differences more deeply. The majority of studies, however, have conceptualized IDS monolithically, granting little attention to a potentially key distinction in how IDS manifests across cultures during the first two years. This study examines and quantifies for the first time differences within IDS in the use of baby register (IDS/BR), an acoustically identifiable type of IDS that includes features such as high pitch, long duration, and smooth intonation (the register that is usually assumed to occur in IDS), and adult register (IDS/AR), the type of IDS that does not include such features and thus sounds as if it could have been addressed to an adult. We studied IDS across 19 American and 19 Lebanese mother-infant dyads, with particular focus on the differential use of registers within IDS as mothers interacted with their infants ages 0-24 months. Our results showed considerable usage of IDS/AR (>30% of utterances) and a tendency for Lebanese mothers to use more IDS than American mothers. Implications for future research on IDS and its role in elucidating how language evolves across cultures are explored.

Maternal input and lexical development: the case of deaf pre-schoolers.

BACKGROUND: Mothers facilitate their young hearing children's word learning by making reference explicit for novel words through physical designation (e.g., with deictic gestures) and by isolating words in simple syntactic frames. As children's language skills develop, such modifications decrease. Less is known about hearing mothers' support to their language-delayed deaf children. AIMS: The current study investigated whether hearing mothers tailored their input to suit their deaf children's word-learning ability as well as their children's word knowledge. METHODS & PROCEDURES: Maternal input to 25 oral deaf children was examined. Word-learning ability was assessed in an experimental task that tested the children's ability to novel map (i.e., infer that a novel word refers to a novel object without physical designation). Word knowledge was assessed by maternal report. OUTCOME & RESULTS: Mothers whose children did not infer word meaning through novel mapping made meaning more explicit than mothers of children who could learn through novel mapping. Specifically, these mothers were more likely to designate referents physically and use simple syntax. For all children, mothers were more likely to make the meaning of novel words more transparent than familiar words. CONCLUSIONS & IMPLICATIONS: The results indicate that hearing mothers were sensitive to the needs of their deaf children. This sensitivity was to children's word knowledge. Mothers seemed aware of what words were in their children's lexicon. Mothers did not rely on their children's ability to use novel mapping, even for the linguistically advanced children.