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 one of three groups: passive exposure to English infant-directed lullabies and readings (English-enrichment, control group); contingent exposure by active sucking on a sensor-equipped pacifier to infant-directed French lullabies and readings (English environment, French-contingent learning) or Mandarin lullabies and readings (English environment, Chinese-contingent learning). The main outcome measures were pre- and post-intervention event-related potentials (ERPs) in response to standardized speech syllables in each language. Results Forty-one subjects completed the study: 15 in English-enrichment control, and 13 each in French-contingent and Chinese-contingent groups. Median gestational age at birth was 34 (IQR 8.75) weeks; postmenstrual age at intervention ranged from 36-46 weeks and was similar across groups. Post-intervention ERP mean amplitude to pairs of English speech sounds across the 3 groups was not different. However, ERP amplitude in French sound differentiation was greater in the French-contingent group than in the Chinese-contingent or English-enrichment groups, and greater in Chinese sound differentiation in the Chinese-contingent group compared with French-contingent and English-enrichment 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.