This is a fascinating study from Columbus Ohio in mildly preterm babies when they reached term. (Richard C, et al. Randomized Trial to Increase Speech Sound Differentiation in Infants Born Preterm. J Pediatr. 2021) We know that prematurity and NICU care both have adverse impacts on language acquisition, and these authors wondered if there are ways we can mitigate those impacts. The babies were late preterms who were enrolled at term or slightly after (post-menstrual age of 36 to 52 weeks. They had a normal hearing screen using brainstem responses, and their families spoke only English. The investigators recorded female voices speaking American English, Mandarin Chinese, or French (they don’t say if it was Parisian French or Quebecois), with speech patterns such as those used for speaking to young infants, which they characterise as “a slower rate of speech, higher vocal pitch, simpler sentence structure, more variable prosody (rhythm, stress, and intonation of speech), and elongated vowels.” These are characteristics of infant-directed speech in many languages (and also of speech directed to our pets). The recordings also included lullabies in the relevant language, and the recordings were played to the babies for 15 minutes, twice a day for a couple of weeks.
They then tested the responses by playing synthesized syllables, consisting of a vowel and a consonant, from each of the languages, and measured auditory responses using temporal electrodes, obtaining the responses before and after the intervention.
Using this methodology, they were able to identify the brainstem responses to individual sounds, and also to see if pairs of sounds gave the same response, if responses differed it meant that there was differentiation between the syllable sounds.
What they found was that exposure to the foreign language increased differentiation between pairs of sounds in that language, but not in the other language, and it had no negative effect on differentiation between pairs of English sounds.
As a background, you should realize that preterm infants have been shown to be able to differentiate syllables at 30 weeks gestation, and young infants can differentiate hundreds of speech sounds (phonemes), an ability which we gradually lose as we acquire a language.
This probably explains some of my difficulty in pronouncing French correctly, as I learned to speak French relatively late in life, I had already lost much of my ability to differentiate certain phonemes, an ability which is hard to relearn. To a native French speaker there is a world of difference between “tu” and “tout”, but it is much more difficult for others. Similarly, many native French speakers have great difficulties with my name as “…th” doesn’t exist in French, and their brains have difficulty in figuring out how to make that sound. Which leads to me frequently being called “Keet” or “Kees” by fellows in our program who are from France! Interestingly Quebec natives, who are generally brought up with a massive exposure to English during their infancy, have much less difficulty and can usually manage “Keith”. “th” both as a hard and a soft sound (‘they’ compared to ‘think”) are common phonemes in English, and Quebec infants probably have major exposure to them.
The research seems to give clues to ways that we might, in the future, enhance language development and perhaps overall executive functioning. In general terms, children from bilingual families have language development which mirrors that of unilingual families, if both languages are taken into account, and in the long term have superior language skills. There is evidence that a bilingual upbringing improves executive function, and there is evidence that that applies to preterm babies. At least one study has shown that preterm babies born to bilingual families have enhanced executive function skills copmared to the monolingual (Baralt M, Darcy Mahoney A. Bilingualism and the executive function advantage in preterm-born children. Cogn Dev. 2020;55).
Exposure to human speech during the NICU stay seems to improve some indicators of early language development of the premature, (Kostilainen K, et al. Repeated Parental Singing During Kangaroo Care Improved Neural Processing of Speech Sound Changes in Preterm Infants at Term Age. Front Neurosci. 2021;15:686027) and a wide exposure to different types of language, one important example being reading stories to NICU babies (Lariviere J, Rennick JE. Parent picture-book reading to infants in the neonatal intensive care unit as an intervention supporting parent-infant interaction and later book reading. J Dev Behav Pediatr. 2011;32(2):146-52), seems to be beneficial. This new study suggests that we should perhaps extend that to language exposure in more than 1 language; even if the parents aren’t bilingual, it could be that exposing our NICU babies to recorded speech in other languages will be beneficial.
I think it is now clear, even as research is ongoing, that reducing exposure to noxious sounds, and increasing exposure to human voice is important for enhancing future development of preterm NICU babies. It is important that we structure our NICU care to allow major exposure to human voices, reading to babies, talking to them using appropriate speech patterns, singing lullabies, and possibly talking to them in a second language. It is one thing we can encourage parents to do in order to be involved in their baby’s care and have a positive impact on their long term outcomes.