Babies of bilingual mothers found to respond to wider range of sounds: Study

NEW DELHI: Newborns of bilingual mothers were found to respond to a wider range of sound pitches, compared to those of mothers speaking one language, according to a new study from Spain.

Researchers said that babies in the wombs of bilingual mothers are expected to be exposed to an environment with a richer variety of sounds than those in the wombs of monolingual mothers.

The researchers found that while the brains of the babies of monolingual mothers had learned to respond in a heightened manner to the pitch of one language, those of the babies of bilingual mothers seem to have become sensitive to a wider range of pitches, without giving a heightened response to any one of them. The findings are published in the journal Frontiers in Human Neuroscience.

Studies have estimated the global bilingual population to be from 43 per cent to over 50 per cent, with bilingualism or multilingualism being the norm in many countries.

"Languages vary in the timing aspects of speech, such as rhythm and accentuation, but also pitch and phonetic information. This means that fetuses from bilingual mothers are expected to be immersed in a more complex acoustic environment than those from monolingual mothers," said co-corresponding author Carles Escera.

Escera is a professor at Sant Joan de Deu Barcelona Children's Hospital, from where the researchers recruited mothers of 131 one-to-three-day-old newborns for the study.

Responding to a questionnaire, 41 per cent of the mothers said they spoke exclusively Spanish or Catalan, which is related to Spanish and spoken in Catalonia in eastern Spain.

The remaining were bilingual - most of them speaking Spanish and Catalan. Other languages spoken by some of the bilingual mothers included Arabic, English, German and Portuguese.

The researchers measured the babies' specific responses to four types of sounds lasting 0.25 seconds long. The sounds were of vowels used in both Spanish and Catalan.

"Here we show that exposure to monolingual or bilingual speech has different effects at birth on 'neural encoding' of voice pitch and vowel sounds: that is, how information about these aspects of speech has been initially learned by the foetus," said co-first author Natalia Gorina-Careta, a researcher at the University of Barcelona.

"At birth, newborns from bilingual mothers appear more sensitive to a wider range of acoustic variation of speech, whereas newborns from monolingual mothers seem to be more selectively tuned to the single language they have been immersed in," said Gorina-Careta.

The findings stress the importance of exposure of foetuses to language for recognising speech sounds at birth, according to Escera.

However, the "sensitive" period for learning languages lasts long after birth, and thus experiences after birth may overshadow the initial changes experienced in the womb, the researchers said.