Year in Review: Language learning starts before birth

Babies seem familiar with vowels, words heard while in womb


Parents are usually careful to watch their language around young children. Maybe parents-to-be ought to watch what they say, too. Not only do babies slurp up language skills in the first few years of life, but new research also suggests that this precocious language learning starts in the womb.

In the later months of pregnancy, fetuses can detect and remember songs, native vowel sounds and entire words. These surprisingly sophisticated linguistic feats offer a new perspective on early learning. The results also raise the possibility of taking steps during pregnancy to help babies at risk for language problems.

Toward the end of pregnancy, sounds from the outside world can seep into a developing fetus’s brain. Young babies show a clear preference for the sounds of their mothers’ voices, familiar nursery rhymes and soothing lullabies, for instance. Four months after birth, babies who had heard “Twinkle, Twinkle Little Star” while in the womb remembered and recognized the lullaby, cognitive neuroscientist Eino Partanen of the University of Helsinki and colleagues reported October 30 in PLOS ONE. The music doesn’t need to be baby-friendly, either. An earlier study found that babies born to mothers who had been hooked on a soap opera during pregnancy stopped fussing when the theme song started.

The findings extend the boundaries of what and when fetuses can learn. “We just don’t know the limits,” says psychologist Christine Moon of Pacific Lutheran University in Tacoma, Wash., who coauthored one of the new studies.

Moon and her colleagues found that fetuses learn to discern native vowel sounds from foreign ones. To catch babies before they had time to familiarize themselves with the outside world, the scientists studied Swedish and U.S. babies seven to 75 hours after birth. These newborns were hooked up to special pacifiers that detected sucking rates. The more sucking, the more unusual a sound was, the researchers reasoned.

Babies sucked more for foreign vowel sounds, Moon and her team reported in Acta Pædiatrica (SN: 2/9/13, p. 9), showing that the babies had grown familiar with native vowels while in the womb.

Fetal learning doesn’t stop at vowels. Fetuses grew familiar with an entire made-up word, Partanen and colleagues reported in the Proceedings of the National Academy of Sciences (SN: 10/5/13, p. 15). In the last trimester, pregnant women blasted a recording of a researcher saying a fake word. Testing the babies’ brain responses with electrodes soon after birth, a neural signature of familiarity called the mismatch response showed up in those who had heard the word during gestation. These babies’ brains showed a big neural response when a syllable in the fake word was pronounced differently, suggesting that the normal version was familiar.

Such knowledge about fetal learning could one day lead to specially designed audio tracks that could boost language skills in fetuses at risk for language impairments such as dyslexia. Carefully crafted auditory cues played during pregnancy might stimulate the growing brain in a way that aids language skills.

The new work also draws attention to the importance of the acoustical environment for a fetus. Because the fetal brain is sensitive to sounds, constant exposure to a noisy environment might be problematic. Loud, unstructured noise could mask this early language acquisition and interfere with normal brain development.

See all top science stories of 2013 

Laura Sanders is the neuroscience writer. She holds a Ph.D. in molecular biology from the University of Southern California.

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