Researchers have discovered that babies can perceive multiple languages while still in the womb.

Prenatal exposure to multiple languages appears to affect newborns' sensitivity to different sound pitches.

The study was conducted in Catalonia, where nearly half the population is bilingual in Catalan and Spanish. 

The researchers recruited mothers of 131 newborns from Sant Joan de Déu Barcelona Children’s Hospital. 

Of these mothers, 41 per cent spoke exclusively Catalan or Spanish during their pregnancy, while the remaining 59 per cent used two languages. 

The researchers placed electrodes on the babies' foreheads to measure their brain responses to specific sounds, which were chosen to be audible in the womb.

Dr Natàlia Gorina-Careta, a researcher at the Institute of Neurosciences, says that “exposure to monolingual or bilingual speech has different effects at birth on ‘neural encoding’ of voice pitch and vowel sounds.” 

Babies from bilingual mothers were shown to be more sensitive to a wider range of pitches, while those from monolingual mothers are more finely tuned to the pitch specific to their single language.

The study used a sound stimulus composed of the vowels /o/ and /a/, which appear in both Spanish and Catalan phonetics. 

These sounds were chosen due to their low frequency, which transmits well through the womb. 

By measuring the frequency-following response (FFR), which tracks how neurons in the auditory cortex and brainstem mimic sound wave features, the researchers found distinct differences. 

Newborns from monolingual mothers exhibited a more defined FFR, indicating their brains were more effectively trained to pick up specific sounds. 

In contrast, babies from bilingual mothers showed sensitivity to a broader range of pitches, albeit with less specificity.

These results underscore the importance of prenatal language exposure for early speech learning. 

“Our data show that prenatal language exposure modulates the neural encoding of speech sounds as measured at birth,” said Dr Carles Escera, a corresponding author of the study.

This suggests a trade-off between efficiency and selectivity in language learning, with bilingual exposure leading to broader sensitivity at the cost of specific tuning.

However, Dr Jordi Costa Faidella cautioned against drawing immediate conclusions for multilingual parents. 

“The sensitive period for language acquisition lasts long after birth,” he said, noting that postnatal experiences may significantly influence language development.

Still, the researchers say that the study's findings open new avenues for exploring how early bilingual exposure affects language learning in the first years of life. 

Further research may help to fully understand these impacts and to provide clearer guidance for multilingual families.

The full study is accessible here.