Poster A40, Saturday, March 24, 1:30–3:30 pm, Exhibit Hall C
Neural Correlates of the "30 Million Word Gap": Children's language exposure is related to white matter structure
Rachel Romeo1,2, Joshua Segaran2, Julia Leonard2, Sydney Robinson2,3, Meredith Rowe4, Allyson Mackey3, John Gabrieli2,4; 1Harvard University, Division of Medical Sciences, 2Massachusetts Institute of Technology, 3University of Pennsylvania, 4Harvard Graduate School of Education
Behavioral research has shown that the quantity and quality of young children’s language input predicts their later linguistic ability, and that children from lower socioeconomic status (SES) backgrounds receive less language exposure than their higher SES peers, which translates into a measurable gap in children’s language skills. The present study investigated which structural neural mechanisms underlie this input-output relationship. Forty SES-diverse children aged 4-6 years completed verbal and nonverbal standardized assessments, followed by a diffusion-weighted imaging (DTI) scan. Families then completed two full weekend days of real-world audio recordings from the child’s perspective, from which three measures were derived: the number of words spoken by any adult, the number of child utterances, and the number of conversational turns between the child and any adult. Behaviorally, SES was strongly correlated with both language exposure and verbal and nonverbal scores. However, when SES was partialled out, only conversational turns predicted additional variance in children’s verbal scores, even when additionally controlling for adult words and child utterances. Furthermore, the number of conversational turns, independent of SES, was positively correlated with the fractional anisotropy (FA) of the left arcuate fasciculus, which connects “Broca’s” and “Wernicke’s” area. This suggests that some qualitative aspect of dialogic communication has a greater impact children’s brain and behavior than the sheer volume of adult speech. To our knowledge, this is the first evidence directly linking children’s language environments with a brain structure known to underlie language development, and which may in turn contribute to the SES language gap.
Topic Area: LANGUAGE: Development & aging