Do we literally start learning our mother tongues from inside the womb? According to a recent study from the University of Kansas, prenatal sensitivity to the rhythmic properties of language may provide children with one of the very first building blocks in acquiring language.
“Research suggests that human language development may start really early — a few days after birth,” said Utako Minai, associate professor of linguistics and team leader for the study. “Babies a few days old have been shown to be sensitive to the rhythmic differences between languages. Previous studies have demonstrated this by measuring changes in babies’ behavior; for example, by measuring whether babies change the rate of sucking on a pacifier when the speech changes from one language to a different language with different rhythmic properties.
“This early discrimination led us to wonder when children’s sensitivity to the rhythmic properties of language emerges, including whether it may, in fact, emerge before birth,” Minai said. “Fetuses can hear things, including speech, in the womb. It’s muffled, like the adults talking in a ‘Peanuts’ cartoon, but the rhythm of the language should be preserved and available for the fetus to hear, even though the speech is muffled.”
Minai said there was already a study that suggested fetuses could discriminate between different types of language, based on rhythmic patterns, but none using the more accurate device available at the Hoglund Brain Imaging Center at KU Medical Center called a magnetocardiogram (MCG).
“The previous study used ultrasound to see whether fetuses recognized changes in language by measuring changes in fetal heart rate,” Minai said. “The speech sounds that were presented to the fetus in the two different languages were spoken by two different people in that study. They found that the fetuses were sensitive to the change in speech sounds, but it was not clear if the fetuses were sensitive to the differences in language or the differences in speaker, so we wanted to control for that factor by having the speech sounds in the two languages spoken by the same person.”
Using fetal biomagnetometry this study measured changes in fetal heart rate to assess discrimination of two rhythmically different languages (English and Japanese). Two-minute passages in English and Japanese were read by the same female bilingual speaker. English and Japanese are argued to be rhythmically distinctive. English speech has a dynamic rhythmic structure resembling Morse code signals, while Japanese has a more regular-paced rhythmic structure.
Sure enough, the fetal heart rates changed when they heard the unfamiliar, rhythmically distinct language (Japanese) after having heard a passage of English speech, while their heart rates did not change when they were presented with a second passage of English instead of a passage in Japanese.
This effect indicates that fetuses are sensitive to the change in language from English to Japanese. These findings provide the first evidence for fetal language discrimination as assessed by fetal biomagnetometry and support the hypothesis that rhythm constitutes a prenatally available building block in language acquisition.