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.”