Four-month-old babies can distinguish between different languages merely by studying the facial movements of the speaker, according to a pioneering study of speech development in infants.
The researchers believe that this "visual speech" ability is a critical component of language learning and is something that is retained for longer in babies brought up in bilingual homes.
Apart from the sounds made by a talking face, babies appear to be able to use the movements to determine whether someone has switched from one language to another, the researchers found.
The study was based on three groups of infants from monolingual, English-speaking families at different ages of life - four, six and eight months.
Two other groups of the same ages, but this time from bilingual English-French families, were also used. The scientists showed each group silent video clips of three bilingual French-English speakers who recited sentences first in English or French, and then switched to the other language.
The young age groups, at four and six months, from both monolingual and bilingual homes were able to tell the languages apart, based on the fact that they would watch the clips for significantly longer periods if the speaker switched language.
However, at eight months, the babies from the monolingual homes appeared to lose this ability. Yet the babies from bilingual families were still able to tell each language apart based on the visual information alone.
The study concluded that young babies needed to use "visual speech" as part of the language-learning process, but they lost this as they got older because the auditory aspect becomes more important. - London Independent