https://www.liveaction.org/news/study-mothers-voice-stimulates-premature-babies-brain
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Stanford researchers followed 46 infants born more than eight weeks prematurely, with participants ranging from 24 to 31 weeks gestation.
Mothers of these children each recorded themselves reading the Paddington Bear story. The 10-minute audio was then played twice an hour for eight hours for the infants in the treatment group, resulting in an additional two hours and 40 minutes per day of hearing the mothers' voices..''