Post written by François Grosjean.
Have you ever observed infants raised in a two-language home when they look at someone speaking to them? I have had that opportunity lately and what has struck me is both the intensity of their gaze and the attention they pay to the mouth, but also to the eyes, of the speaker. But is this simply a figment of my imagination or is there some truth to it?
The attention that infants pay to talking faces when learning to speak, and the evolution of their behavior during their first year, is a relatively new topic in the field of child development. Let's first look at monolingual infants. Researchers David Lewkowicz and Amy Hansen-Tift reported on a study a few years ago that tracked what happened to the infants' eye gaze while they watched and listened to a person reciting a prepared monologue.
The authors looked at several groups of infants as well as one group of adults. The infants either sat in an infant's seat or on their parent's lap, and watched a person uttering an English monologue on a computer monitor. As they were doing so, the researchers monitored where the babies looked by using an eye tracker. They were interested in two main areas on the speaker's face: one around the eyes and one around the mouth.
In reporting the results they obtained, we will concentrate on the infants who were 4, 8, and 12 months old. At 4 months old, infants looked longer at the eyes, but then a shift took place so that by 8 months old, they looked longer at the mouth. Then, during the next few months, a second shift occurred so that infants who were 12 months old looked for an equal amount of time at both the mouth and the eyes.
The researchers explained the first shift towards the mouth by the fact that as they are learning how to speak, infants are attracted by the auditory AND the visual speech signals that are produced by the speaker and that are perceptually salient and redundant. As for the second shift, back to the eyes, the infants' emerging speech output reduces their need to have direct access to both the visual and auditory speech cues, and they can now concentrate on various social cues available in the speaker's eyes (shared meanings, beliefs, and desires).
But what about bilingual infants who are brought up with two languages? A recent study by researchers Ferran Pons and Laura Bosch, along with David Lewkowicz of the monolingual study, gives us the answer. The authors hypothesized that because bilingual infants need to process two languages, and keep them apart, they may well use audiovisual speech cues more than monolingual infants.
Since this study was undertaken in Barcelona, Spain, where different languages are used (Catalan and Spanish), the authors first tested three groups of monolingual infants, 4, 8, and 12 months old, who were being brought up with either Calalan or Spanish only. They used the same procedure as in the preceding American study and found similar results: The 4-month-old infants looked longer at the eyes, the 8-month-olds longer at the mouth, and the 12-month-olds equally at the mouth and the eyes.
The next step was to test bilingual infants who belonged to the same three age groups but who were being brought up with a native (dominant) language—either Spanish or Catalan—and who were also exposed to another language for at least 25 percent of the time. For the Spanish native language group, the other language was Catalan, and for the Catalan native language group, the other language was Spanish. Of course, these bilingual infants watched two videos, one in each of their languages.
The results obtained were fascinating. In both languages, the 4-month-old bilingual infants looked equally at the eyes and the mouth (recall that the monolingual infants of that age group looked more at the eyes), the 8-month-olds looked longer at the mouth (as did the monolinguals), and the 12-month-olds again looked longer at the mouth (whereas the monolinguals looked equally at the mouth and the eyes).
How do the researchers explain the differences between bilingual and monolingual infants? The greater perceptual salience of audiovisual speech cues helps bilingual infants identify distinct language-specific features that keep the languages apart. Four-month old infants become aware of this, hence their earlier attentional shift to the mouth, even though they also look at the eyes a lot. Attention to the talkers' mouth increases from then on and continues throughout their first year since redundant audiovisual speech cues are of primary importance for these children. In a word, bilingual infants exploit the perceptual information of these cues earlier and for a longer period of time than monolingual infants. (For other cues and strategies used during the discrimination and separation of languages, see here).
The authors end their paper with two questions that now need to be studied: Will bilingual children continue to rely on audiovisual speech cues past 12 months of age, and will children who are acquiring more dissimilar languages take even greater advantage of these redundant cues? As we await the answers, let's not forget to continue observing where it is bilingual infants look when we speak to them; it is simply amazing!
For a full list of "Life as a bilingual" blog posts by content area, see here.
Photo of a mother playing with cute little baby from Shutterstock.
Lewkowicz, David J. & Hansen-Tift, Amy M. (2012). Infants deploy selective attention to the mouth of a talking face when learning speech. Proceedings of the National Academy of Sciences of the United States of America, 109 (5), 1431–1436.
Pons, Ferran, Bosch, Laura & Lewkowicz, David J. (2015). Bilingualism modulates infants’ selective attention to the mouth of a talking face. Psychological Science, 26(4), 490–498.
François Grosjean's website.