You could be bilingual without knowing it, or rather your brain could. During the first years of life, the brain has an amazing learning capacity that leaves an indelible mark. In fact, scientists have discovered that people who only speak one language but were exposed to another language early in life present the same brain activity as bilinguals.

Lara Pierce's team from the University of Washington in Seattle wanted to know if our experiences during the early years of our lives leave long term traces in our brains. In this study, she was particularly interested in the impact of language.

This study involves Chinese-born children between the ages of 9 and 17 who were adopted at an average age of 12.8 months by monolingual French speaking families. These children were never exposed to the Chinese language following adoption and had no conscious memories of the language.

Images of their brains were recorded while they were listening to Chinese sounds. These images were then compared to French monolinguals and to French-Chinese bilinguals.

The adopted children taking part in the study were incapable of speaking or understanding Chinese, but their brains showed the same activity as the bilinguals who spoke Chinese and French fluently. Conversely, while the children themselves were monolingual, their brain activity was different from those who only spoke French.

Therefore, the language we hear during the first year after birth has a considerable impact on our neuronal mechanisms for many years; the effect could last a lifetime. This phenomenon could apply to any skill learned early in life that is subsequently forgotten. More generally, this raises the question of the unconscious influence of any early experience on future development.