Linguistic Input and Child Vocalization of 7 Children from 5 to 30 Months: A Longitudinal Study with LENA Automatic Analysis

This study examined longitudinal changes in linguistic input, conversational turns, and child vocalizations in Chinese-speaking families using the computerized LENA (Language Environment Analysis) software, a system that captures audio data in children's natural environment and parses out speech data automatically. All-day home recordings (11-16 hours) from seven typically developing Chinese-learning children (two males and five females) at the ages of 5, 10, 14, 21, and 30 months were analyzed. Adult word count (AWC), conversational turn count (CT), and child vocalization count (CV) of 70 recordings (i.e., 7 children x 5 ages x 2 recordings) were retrieved from the LENA software. These recordings included times when families were asleep. As a result, the present study also compared the results with and without LENA-determined silence time (i.e., quiet and sleep time). The results showed that the percentage of silence in the recordings decreased with age, indicating that the children's awake time increased as they age. When the children were awake, they listened to an average of 1734 adult words, engaged in 39 conversational turns, and produced 150 vocalizations per hour from 5 to 30 months of age. The CV and CT increased with age, while the AWC did not show a clear pattern, which was similar to English normative estimates from Gilkerson and Richards (2008). The CT was also found to be a more effective contributor to the number of CV than AWC, indicating that speech produced in temporal proximity to children's vocalizations or directed to children played an important role in eliciting child vocalizations.