Demystifying infant vocal imitation: The roles of mouth looking and speaker's gaze

Neurodevelopmental Outcomes in Preterm Infants at 18 Months of Corrected Age Following Coronavirus Disease 2019 (COVID-19) Pandemic-Related Neonatal Intensive Care Unit (NICU) Care Changes

BACKGROUND

 The coronavirus disease 2019 (COVID-19) pandemic led to significant changes in neonatal intensive care unit (NICU) protocols, including restrictions on parental visitation and suspension of kangaroo mother care. These modifications likely impacted preterm infants' neurodevelopmental outcomes. While previous studies have examined the short-term developmental effects of the pandemic, the long-term neurodevelopmental consequences remain unclear. This study aimed to assess the impact of pandemic-related NICU care changes on the neurodevelopmental outcomes of preterm infants at 18 months corrected age in Japan.

METHODOLOGY

 This retrospective, single-center study was conducted at a Japanese university hospital and included preterm infants born before and during the COVID-19 pandemic. Eligible infants were those with a gestational age of less than 32 weeks or a birth weight under 1,500 g, who subsequently underwent neurodevelopmental assessment at 18 months of corrected age using the Kyoto Scale of Psychological Development 2001 (KSPD). Infants were categorized into a prepandemic group (born before March 1, 2020) and a pandemic group (born on or after March 1, 2020). To compare demographic and clinical characteristics between the groups, the Mann-Whitney U test was employed for continuous variables and the chi-square test for categorical variables. All statistical analyses were performed using a predefined significance level of p < 0.05.

RESULTS

 A total of 44 preterm infants were included (22 per group). While there were no significant differences in birth weight or neonatal morbidities between the groups, the pandemic group had a significantly older gestational age (30 vs. 28 weeks, p = 0.04). KSPD assessments revealed that the pandemic group had significantly lower cognitive-adaptive (80 vs. 92, p = 0.01) and language-social (73 vs. 89, p = 0.04) developmental quotients (DQ) compared with the prepandemic group. Postural-motor DQ was lower in the pandemic group but did not reach statistical significance (82 vs. 98, p = 0.14). To account for potential confounders, an analysis of covariance was conducted, adjusting for gestational age, birth weight, and sex. The adjusted analysis remained consistent with the unadjusted findings, confirming significantly lower cognitive-adaptive DQ (F = 4.83, p = 0.03) and language-social DQ (F = 3.94, p = 0.04) in the pandemic group. Gestational age, birth weight, and sex were not significantly associated with any DQ scores.

CONCLUSIONS

 Preterm infants born during the COVID-19 pandemic exhibited significantly lower cognitive-adaptive and language-social DQs at 18 months corrected age than prepandemic infants. These findings suggest that pandemic-related restrictions on parental involvement in the NICU may have potentially influenced neurodevelopment. Further research is needed to explore long-term developmental trajectories and interventions to support optimal outcomes in this vulnerable population.

The Role of Talking Faces in Infant Language Learning: Mind the Gap between Screen-Based Settings and Real-Life Communicative Interactions

Over the last few decades, developmental (psycho) linguists have demonstrated that perceiving talking faces audio-visually is important for early language acquisition. Using mostly well-controlled and screen-based laboratory approaches, this line of research has shown that paying attention to talking faces is likely to be one of the powerful strategies infants use to learn their native(s) language(s). In this review, we combine evidence from these screen-based studies with another line of research that has studied how infants learn novel words and deploy their visual attention during naturalistic play. In our view, this is an important step toward developing an integrated account of how infants effectively extract audiovisual information from talkers' faces during early language learning. We identify three factors that have been understudied so far, despite the fact that they are likely to have an important impact on how infants deploy their attention (or not) toward talking faces during social interactions: social contingency, speaker characteristics, and task- dependencies. Last, we propose ideas to address these issues in future research, with the aim of reducing the existing knowledge gap between current experimental studies and the many ways infants can and do effectively rely upon the audiovisual information extracted from talking faces in their real-life language environment.

Motor constellation theory: A model of infants' phonological development

Every normally developing human infant solves the difficult problem of mapping their native-language phonology, but the neural mechanisms underpinning this behavior remain poorly understood. Here, motor constellation theory, an integrative neurophonological model, is presented, with the goal of explicating this issue. It is assumed that infants' motor-auditory phonological mapping takes place through infants' orosensory "reaching" for phonological elements observed in the language-specific ambient phonology, via reference to kinesthetic feedback from motor systems (e.g., articulators), and auditory feedback from resulting speech and speech-like sounds. Attempts are regulated by basal ganglion-cerebellar speech neural circuitry, and successful attempts at reproduction are enforced through dopaminergic signaling. Early in life, the pace of anatomical development constrains mapping such that complete language-specific phonological mapping is prohibited by infants' undeveloped supralaryngeal vocal tract and undescended larynx; constraints gradually dissolve with age, enabling adult phonology. Where appropriate, reference is made to findings from animal and clinical models. Some implications for future modeling and simulation efforts, as well as clinical settings, are also discussed.

The ontogeny of human laughter

Human adult laughter is characterized by vocal bursts produced predominantly during exhalation, yet apes laugh while exhaling and inhaling. The current study investigated our hypothesis that laughter of human infants changes from laughter similar to that of apes to increasingly resemble that of human adults over early development. We further hypothesized that the more laughter is produced on the exhale, the more positively it is perceived. To test these predictions, novice (n = 102) and expert (phonetician, n = 15) listeners judged the extent to which human infant laughter (n = 44) was produced during inhalation or exhalation, and the extent to which they found the laughs pleasant and contagious. Support was found for both hypotheses, which were further confirmed in two pre-registered replication studies. Likely through social learning and the anatomical development of the vocal production system, infants' initial ape-like laughter transforms into laughter similar to that of adult humans over the course of ontogeny.

Reliability of Listener Judgments of Infant Vocal Imitation

There are many theories surrounding infant imitation; however, there is no research to our knowledge evaluating the reliability of listener perception of vocal imitation in prelinguistic infants. This paper evaluates intra- and inter-rater judgments on the degree of "imitativeness" in utterances of infants below 12 months of age. 18 listeners were presented audio segments selected from naturalistic recordings to represent in each case a parent vocal model followed by an infant utterance ranging from low to high degrees of imitativeness. The naturalistic data suggested vocal imitation occurred rarely across the first year, but strong intra- and inter-rater correlations were found for judgments of imitativeness. Our results suggest salience of the infant's vocal imitation despite its rare occurrence as well as active perception by listeners of the imitative signal. We discuss infant vocal imitation as a potential signal of well-being as perceived by caregivers.