Mother tongue, other tongue--they may all sound like gobbledygook to babies, but new research shows that infants can tell if someone switches to an unfamiliar language just by studying the speaker's face. The babies apparently rely on how the face moves, not just the sound of the words, to pick up on a foreign language. Further, scientists found, infants will likely lose that knack before their first birthday if they're not in a bilingual family that constantly exposes them to language switching.
Even if they don't understand the words, babies notice when they hear an unfamiliar language, many studies have shown. Whitney Weikum, a doctoral student studying linguistics development in infants at the University of British Columbia (UBC) in Vancouver, Canada, wondered if they could tell just by looking.
To test this theory, Weikum, cognitive development psychologist Janet Werker, also of UBC, and their colleagues turned to infants aged 4, 6, or 8 months. Twenty-four of the babies came from homes where parents spoke both English and French, and 36 others had English-speaking parents. The babies watched muted video clips of people speaking English and then switching to French.
The team found that when the 4- and 6-month-olds grew used to watching a clip of one language, they would quickly tire of seeing it onscreen. But they would pay attention to the other language for longer whether their home was bilingual or not, indicating that they noticed a difference. That changed by 8 months. There, babies from monolingual homes spent as little time watching someone speak the second language as the first. But bilingual 8-month-olds kept watching after the language switched, indicating that they always noticed a difference. A control group of 36 babies exposed to video clips of different English sentences confirmed that the variation in attention span among the other babies was due to language, not what was being said.
"We were surprised by the decline at 8 months," says Weikum. "We went into it expecting their ability to improve over the first year of life and continue to do it as adults." She notes that this waning points to use-it-or-lose-it programming: "They've only seen one language, so they never need to figure out what the other one is." The team reports their findings in the 25 May Science.
It's a surprise that babies tune their language development not only to sounds they hear, but also to speech they see, says Olivier Pascalis, a language development specialist at University of Sheffield, U.K. Erin Hannon, a development psychologist at Harvard University, finds it even more interesting that the babies lose the ability, because she thought it would remain as the babies became more comfortable understanding their native language. Weikum says she is planning to investigate whether the babies are attuned to the rhythmic differences or to the face shape characteristic of syllables.