Parental verbal responsiveness to infant vocalizations from 9 to 14 months of age

Early developmental changes in infants' vocal responses in interactions with caregivers

OBJECTIVES

The study aimed to explore the developmental trajectory of infants' vocal responses and the temporal characteristics of vocal interactions between infants and caregivers in natural home environments, focusing specifically on Korean infants aged 3, 6, 9, and 12 months.

METHODS

One-day home recordings were collected using a LENA recorder at ages 3, 6, 9, and 12 months for each infant. In-depth analyses of the LENA recordings were conducted on 20 5-minute segments that showed the highest conversational turn counts, as determined by the LENA automated analysis. The temporal characteristics of infant vocalizations during interactions with caregivers were examined through infant vocal response, vocal response latency, and overlapping vocalizations.

RESULTS

The results indicated that the proportion of infant vocal responses following adult speech differed across age groups. Specifically, the highest proportion was observed at 3 months, with a noticeable decrease at 6 and 9 months, and a slight increase at 12 months. Infant vocal response latency increased with age, indicating longer response delays as infants got older. The proportion of overlapping vocalizations was consistent among 3, 6, and 9-month-olds but decreased significantly at 12 months.

CONCLUSION

These findings highlight distinct changes in infant vocal interactions during the first year of life. Although the analysis was cross-sectional, the observed patterns suggest developmental changes in the timing and structure of vocal response as infants age. This study indicates that infants adapt their vocal interactions in response to caregivers' speech, which may reflect a gradual learning of conversational coordination.

The Predictability of Naturalistic Evaluation of All-Day Recordings for Speech and Language Development

OBJECTIVES

The study aimed to investigate the predictive potential of language environment and vocal development status measures obtained through integrated analysis of Language ENvironment Analysis (LENA) recordings during the prelinguistic stage for subsequent speech and language development in Korean-acquiring children. Specifically, this study explored whether measures from both LENA-automated analysis and human coding at 6-8 months and 12-14 months of age predict vocabulary and phonological development at 18-20 months.

METHOD

One-day home recordings from 20 children were collected using a LENA recorder at 6-8 months, 12-14 months, and 18-20 months. Both LENA-automated measures and measures from human coding were obtained from recordings at 6-8 months and 12-14 months. The number of different words, consonant inventory, and utterance structure inventory were identified from recordings of 18-20 months. Correlation and multiple regression analyses were performed to investigate whether measures related to early language environment and child vocalization at 6-8 months and 12-14 months were predictive of vocabulary and phonological measures at 18-20 months.

RESULTS

The results showed that the two main LENA-automated measures, conversational turn count (CTC) and child vocalization count, were positively correlated with all vocabulary and phonological measures at 18-20 months. Multiple regression analysis revealed that CTC during the prelinguistic stages was the most significant predictor of a number of different words, consonant inventory, and utterance structure inventory at 18-20 months. Also, adult word count in LENA-automated measures, child-directed speech ratio, and canonical babbling ratio measured by human coding significantly predicted some vocabulary and phonological measures at 18-20 months.

CONCLUSION

This study highlights the multifaceted nature of language acquisition and collectively emphasizes the value of considering both quantitative and qualitative aspects of language input to understand early language development in children.