Randomized Trial to Increase Speech Sound Differentiation in Infants Born Preterm

Objective: To test whether infant-directed foreign language active learning would specifically increase speech sound differentiation to the intervention language while not decreasing differentiation in response to English.

Study design: Pilot randomized controlled trial of stable infants born preterm in the newborn intensive care unit with normal auditory brainstem responses, whose parents spoke only English and had no musical training or familial hearing abnormality. Assignment was to 1 of 3 groups: passive exposure to English infant-directed lullabies and readings (English-enrichment, control group) and contingent exposure by active sucking on a sensor-equipped pacifier to either infant-directed French lullabies and readings (English environment, French-contingent learning group) or infant-directed Mandarin lullabies and readings (English environment, Chinese-contingent learning group). The main outcome measures were preintervention and postintervention event-related potentials (ERPs) in response to standardized speech syllables in each language.

Results: Forty-one subjects completed the study, including 15 in the English-enrichment control group and 13 each in the French-contingent and Chinese-contingent groups. The median gestational age at birth was 34 weeks (IQR, 8.75 weeks); postmenstrual age at intervention ranged from 36 to 46 weeks and was similar across the 3 groups. Postintervention mean ERP amplitude to pairs of English speech sounds did not differ across the 3 groups; however, ERP amplitude in French sound differentiation was greater in the French-contingent group than in the Chinese-contingent or English-enrichment groups, and ERP amplitude greater in Chinese sound differentiation was greater in the Chinese-contingent group compared with the other 2 groups.

Conclusion: Contingent infant-directed foreign language exposure increased speech sound differentiation specific to the intervention language and did not decrease differentiation in response to English.

Trial registration: ClinicalTrials.gov: NCT03232931.