Canadian researchers say that babies as young as 4 months of age know the difference between English and French by looking for visual cues.
The researchers at McGill University, British Columbia, say babies are able to differentiate between the English and French language without actually hearing it.
The researchers say the study is the first to show that young babies are able to tell languages apart by using only visual information.
In a study led by Dr. Janet Werker, a psychology professor at UBC, a team of scientists experimented on 100 babies.
The babies were placed into five sets; three sets of babies age 4, 6 and 8 months were all from english speaking homes and two sets of babies age 6 and 8 months were from bilingual homes.
Each group of babies were shown video clips without audio in which three french-english speakers spoke, first in one of the two main languages of Canada, either English or French, and then switched to the other.
The researchers found that the visuals without audio were enough for the babies, from four to six months, to watch the videos more attentively and for a longer time whenever the speakers changed over to the other language.
However by eight months it was only the babies from bilingual homes and who were accustomed to both languages, who were able to distinguish the languages visually.
The researchers believe that by eight months only babies exposed to more than one language retain this ability as compared to babies who no longer needed or used it and therefore gradually lost it.
The researchers do say they were not able to tell how or why the babies could tell there was a difference in language without hearing them but suggest it is the different rhythms of the language and the way that people move their mouths when they talk, which they pick up on.
The study is published in the journal Science.