Learning a foreign language—before you’re born!

Sixty native-French-speaking women with uncomplicated pregnancies were recruited to participate in the study. Each was given an MP3 player containing a recording of a short tale in two languages, French and either German or Hebrew. 

Why these specific languages? “We were looking for languages that were acoustically and phonologically different from French, and could be read by the same person to avoid voice bias,” René explained. “We were fortunate to find a trilingual speaker.”

Starting in the 35th week of pregnancy, the participants placed the headphones on their stomachs, while in a quiet environment with no music, and played the recordings for their babies. The babies heard the stories an average of 25 times.

Between 10 and 78 hours after birth, the researchers played the same story again for the newborns, this time in all three languages: their native French, the foreign language to which they had been exposed in utero, and a completely unfamiliar language.

To measure the infants’ brain responses, the researchers used functional near-infrared spectroscopy (fNIRS), a non-invasive technique that records blood oxygenation in the cerebral cortex. 

“A device that looks like a swim cap lined with lights is placed on the baby’s head,” René explained. “Light close to the infrared spectrum passes through the tissue to the cortex and sensors detect variations in blood oxygenation levels.”

“We know that when a region of the brain is activated, there is an increase in blood oxygenation, since the brain needs energy, accompanied by a decrease in deoxygenated hemoglobin,” Gallagher added. “We are able to measure these responses in the regions of the brain that process language. We wanted to see whether modifying a baby’s linguistic environment in the womb can shape the brain’s language networks, so we compared brain activation in newborns when hearing their mother tongue, a foreign language to which they had been exposed in utero, and a foreign language they had never heard.”

When the babies heard French, their left temporal cortex was activated, as were other language regions, with a clear predominance in the left hemisphere. That is the same pattern observed in adults. A similar pattern was found when the babies heard the foreign language to which they had been exposed in the womb.

However, the completely unfamiliar foreign language triggered much less brain activity, with no strong predominance in either hemisphere. Therefore, babies a few hours old process a foreign language heard in the womb differently than an entirely unfamiliar foreign language.

“We didn’t know if such brief exposure would have a measurable effect,” said Gallagher. “But we can clearly see that even a few minutes of listening per day for a few weeks is enough to modulate the organization of brain networks.”

These findings confirm the exceptional plasticity of the human brain even before birth. “It shows how malleable language networks are,” Gallagher commented. “But it also reminds us of their fragility: if a positive environment can have an effect, we can suppose that a negative environment would too.”

It is too early to say whether these prenatal stimuli will have a long-term impact. “We are following the children over time,” said René. “Perhaps at four or eight months, the effect will have disappeared, or maybe it will persist.”

This study opens up exciting avenues for research that could improve our general understanding of language development, and potentially support early intervention. “We’re not there yet,” Gallagher cautioned, “but it is conceivable that one day this approach could be used to support vulnerable children or children with developmental disorders.”

For now, one thing is clear: long before they utter their first word, babies have begun to familiarize themselves with language, snug and warm in the womb.