Study: Bilingual infants lip-​​read more than monolingual infants

New research from North­eastern devel­op­mental psy­chol­o­gist David J. Lewkowicz shows that infants learning more than one lan­guage do more lip-​​reading than infants learning a single language.

In the study, bilin­gual and mono­lin­gual infants were observed watching a video of a woman speaking in Spanish or Catalan; the infants were learning one or both of these lan­guages. Lewkowicz and his col­lab­o­ra­tors found that bilin­gual infants focused their atten­tion on the mouth at an ear­lier age and for a longer period of time than mono­lin­gual infants. This sug­gests that bilin­gual infants pick up on salient audio­vi­sual speech cues more than their mono­lin­gual peers to help them dis­tin­guish between the two lan­guages they are learning simul­ta­ne­ously, he said.

These results pro­vide new insights into the under­lying mech­a­nisms of people’s ability to acquire more than one lan­guage at the same time early in life,” said Lewkowicz, a pro­fessor in the Depart­ment of Com­mu­ni­ca­tion Sci­ences and Dis­or­ders in Northeastern’s Bouvé Col­lege of Health Sci­ences.

Lewkowicz and his co-authors—Ferran Pons and Laura Bosch, both at the Uni­ver­sity of Barcelona and the Insti­tute for Brain, Cog­ni­tion, and Behavior in Spain—report these find­ings in a forth­coming paper in the journal Psy­cho­log­ical Sci­ence. Lewkowicz said the find­ings have impor­tant impli­ca­tions for under­standing how infants acquire speech and lan­guage and shed light on how bilin­gual infants—despite their neural and behav­ioral immaturity—manage to learn two dif­ferent lan­guages as easily as mono­lin­gual infants learn one language.

The find­ings, he said, could also play a role in treating and diag­nosing chil­dren with com­mu­nica­tive and learning dis­or­ders like autism. He noted that chil­dren with autism are typ­i­cally diag­nosed between 18 and 24 months and tend to look at faces less often than typ­ical chil­dren, a factor that sig­nif­i­cantly reduces their oppor­tu­ni­ties for expe­ri­encing audio­vi­sual speech that Lewkowicz’s pre­vious research has shown to be impor­tant for young babies. What this means in the con­text of his research is that iden­ti­fying infants with par­tic­ular pat­terns of selec­tive atten­tion to speech could help diag­nose com­mu­ni­ca­tion and learning dis­or­ders ear­lier than is cur­rently possible.

In this new study, Lewkowicz and his col­lab­o­ra­tors used eye-​​tracking tech­nology to mea­sure pre­cisely how much time infants attended to the eyes and mouth—the two crit­ical areas that we focus on during social communication—of a person who could be seen and heard speaking. The infants all lived in Spain and were learning Spanish and/​or Catalan.

The researchers found that, regard­less of what lan­guage the person spoke, 4-​​month-​​old mono­lin­gual babies looked longer at the eyes than the mouth but that 4-​​month-​​old bilin­gual babies looked equally as long at the eyes and mouth. Sim­i­larly, whereas 12-​​month-​​old mono­lin­gual babies looked equally at the eyes and mouth in response to native speech and more at the mouth in response to non-​​native speech, 12-​​month-​​old bilin­gual babies looked longer at the mouth regard­less of lan­guage and, crit­i­cally, longer than mono­lin­gual infants in both cases.

These find­ings build upon Lewkowicz’s ground­breaking research pub­lished in 2012, which showed that babies learn to talk not only by lis­tening to sounds but also by lip-​​reading. Find­ings showed that as babies start to babble—at around six months of age—they begin to shift their atten­tion to the mouth of the person speaking. In essence, they begin to lip-​​read, having dis­cov­ered how much salient speech infor­ma­tion they can learn from watching a person’s mouth.

In the pre­vious study, two exper­i­ments were con­ducted with dif­ferent age groups of mono­lin­gual, English-​​learning infants between 4 and 12 months of age. In these exper­i­ments, the infants watched videos of women speaking either Eng­lish or Spanish. In addi­tion to finding that babies begin to shift their atten­tion to a talker’s mouth after 6 months of age, this study showed that 12-​​month-​​olds attended to the mouth longer when the person spoke Spanish than when she spoke Eng­lish, pre­sum­ably because what had now become an unfa­miliar lan­guage was more dif­fi­cult to understand.

These find­ings led the researchers to pursue this latest study. Upon learning that com­bined audi­tory and visual speech infor­ma­tion is very impor­tant for speech and lan­guage acqui­si­tion in infancy, they won­dered whether babies growing up in a bilin­gual envi­ron­ment take even greater advan­tage of these com­bined audi­tory and visual cues and, thus, whether they lip-​​read even more.

That’s pre­cisely what we found,” Lewkowicz said, adding that “These find­ings shed new light on bilin­gualism, which hap­pens to be of great interest to researchers studying  the effects of early expe­ri­ence as well as pol­i­cy­makers con­cerned with inte­grating non-​​English speaking chil­dren into the classroom.”

Lewkowicz noted that his team’s research offers insight into what kinds of infor­ma­tion to expose chil­dren to in order to help them acquire two lan­guages more effec­tively. Babies, he explained, go through an intense period of learning in the first year and during this time they acquire exper­tise in their native lan­guage. Para­dox­i­cally, while native-​​language exper­tise emerges, babies’ ability to per­ceive other lan­guages declines—a process known as per­cep­tual nar­rowing, he said.

By the end of their first year, infants have nar­rowed their ability to per­ceive dif­ferent lan­guages if they have not had expo­sure to them,” he explained. “This process hap­pens very rapidly and ear­lier than we thought, though chil­dren still retain a great deal of plas­ticity throughout child­hood. But cer­tainly, if you don’t get exposed to another lan­guage during child­hood, you’ll have dif­fi­culty learning it later on.

The flip side of this is that expo­sure to mul­tiple lan­guages in infancy pre­vents nar­rowing, and it is now clear that one way in which bilin­gual infants manage to accom­plish their task is by taking max­imum advan­tage of both audible and vis­ible speech when­ever they interact with their social partners.” Original press release.


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