Study provides clues to how humans learn to communicate
A new study suggests that infants as young as four months old have the ability to differentiate English from French without actually hearing the languages spoken.
Dr. Athena Vouloumanos of McGill University's Department of Psychology co-designed and helped conduct a study in which infants were shown silent videos of people speaking either English or French. The objective was to determine whether infants aged four to eight months could visually distinguish their native language from an unfamiliar one. The results appear in the May 25 edition of the journal Science.
"We found that infants can, in fact, tell the languages apart," said Dr. Vouloumanos, adding the research demonstrates that infants are well equipped to learn multiple languages, and that visual speech alone is sufficient for language discernment in early infancy. "Whether that has implications later in life would be an interesting question for further study, but it's a step toward finding out how humans learn language."
She noted that the ability was no longer evident in eight-month-olds who were only exposed to English in their daily lives, while those considered bilingual (defined, for the purposes of the study, as those regularly exposed to both English and French, Canada's two official languages) continued to discriminate between the two languages. It is unclear exactly why this change occurs, Dr. Vouloumanos said, though she does have a theory.
"There is a lot of circumstantial evidence that suggests many perceptual changes occur in a child's development between the ages of six and ten months, when an infant starts to tune into the perceptual properties of speech in their native language," she said. "We think that for bilingual babies, it's still important to be able to distinguish between both languages, no matter their age," said Dr. Vouloumanos, who began working on the study while she was a PhD student at UBC before joining McGill in 2004.
She and her colleagues, Whitney Weikum and Janet Werker at the University of British Columbia, Jordi Navarra at Oxford University and Salvador Soto-Faraco and Núria Sebastián-Gallés at Spain's Universitat de Barcelona and Institut Catatlà de Recerca based their findings on infants' natural tendency to become bored with a repeated visual display (habituation) and to renew their interest when they are shown something that they perceive as different (dishabituation).
Every trial included a video clip of a different sentence being spoken in one of the two languages. "Babies could control the presentation of the video by their looking behaviour. When the baby would get bored and look away, the screen would turn off. When they looked back, we played them a different sentence. Eventually, babies looked at the screen less and less. At this point, we would then switch the language being spoken and if they detected the change in the language, their looking behaviour would recover," Dr. Vouloumanos explained.
Though they do not yet know how or why infants of that age might be able to discern one language from another without actually hearing the words spoken, the researchers suggest such possibilities as differences in the rhythm of languages and the ways in which certain language-specific sounds are formed by facial features.
"Some adults say that they can tell when people are speaking French because they look like they're kissing when they make 'eu' sounds that don't exist in English," said Dr. Vouloumanos. "It shows us that infants are sensitive to visual properties of spoken language, one more step in putting together a symbolic, multi-modal system of communication."