For many pregnant mothers who play music or speak to their unborn child, a kick might be the only confirmation that the child heard anything at all. But according to a new study, an unborn child does indeed hear everything, including people’s voices, which allows them to begin learning words and remembering them once they’re born.

“If you put your hand over your mouth and speak, that’s very similar to the situation the fetus is in,” Eino Partanen, a cognitive neuroscientist at the University of Helsinki, told Science Magazine. “You can hear the rhythm of speech, rhythm of music, and so on.” For fetuses, whose ability to hear develops around the last trimester of pregnancy, this means that their developing brains can begin to pick up sounds from the outside world.

"Tatata" vs. "Tatota" 

From their 29th week of pregnancy, 17 mothers were given a recording of a woman repeating the word “tatata” hundreds of times. Sometimes the word would also change to “tatota,” a so-called pseudoword “that is important for research. It has three syllables, and we chose such a long word to make it challenging for the small brains to find the changes and give them something difficult to learn,” Mina Huotilainen, co-author of the study, told HealthDay. “Such a word could exist in Finnish. It follows all the rules of Finnish language.”    

The mothers were told to play the recordings five to seven times a week, said in various ways and at different pitches. Overall, the babies had heard the words more than 25,000 times by the time of their birth. The babies were subjected to electroencephalograms (EEG), which were able to test their memories for word recognition through electrodes attached to their head. Those who remembered words showed a stronger response through the scans, compared to 16 babies who acted as controls. What’s more, responses were even stronger when their brains remembered “tatota” — also called a mismatch response, according to ScienceNews. Partanen says that adults also had similar neural reactions when they’re learning a new language.

“The fact that learning from frequently presented sounds occurs while infants are still in the womb means that language learning does not begin on day one at the moment of birth, but while the infant listens to sounds in utero. It’s really quite amazing that the fetal brain has that capacity,” Patricia Kuhl, director of the University of Washington’s National Science Foundation Science of Learning Center, told HealthDay. She was not involved with the study.

Unborn Babies Learning Vowels

The findings build on previous research, that found that babies were able to hear vowels while in the womb, and remember them after they were born. For the study, babies listened to vowel sounds in their native language (either Swedish or English) and then in the other, foreign language. The researchers tested for recognition by using a pacifier hooked up to a computer. When babies heard sounds they weren’t familiar with, they became interested in the new sounds and tended to suck on the pacifiers more. This study and others, however, relied heavily on babies’ behaviors rather than their neural reactions.

“The better we know how the fetus’ brain works, the more we’ll know [about] early development of language,” Partanen told NBC. “If we know better how language develops very early, we may one day be able to develop very early interventions [for babies with abnormal development].”

Source: Partanen E, Kujala T, Huotilainen M, et al. Learning-induced neural plasticity of speech processing before birth. PNAS. 2013.