Speaking two languages rather than just one has obvious practical benefits in an increasingly globalized world. But in recent years, scientists have begun to show that the advantages of bilingual- ism are even more fundamental than being able to converse with a wider range of people. Being bilingual, it turns out, makes you smarter. It can have a profound effect on your brain, improving cognitive skills not related to language and even shielding against dementia in old age.

    This view of bilingualism is remarkably different from the understanding of bilingualism through much of the 20th century. Researchers, educators and policy makers long considered a second language to be an interference that hindered a child’s academic and intellectual development.

    They were not wrong about the interference: there is ample evidence that in a bilingual’s brain both language systems are active even when he is using only one language, thus creating situations in which  one  system  obstructs  the  other.  But  this  interference,  researchers  are  finding  out,  isn’t  so much a handicap as a blessing in disguise. It forces the brain to resolve internal conflict, giving the mind a workout that strengthens its cognitive muscles.

    A collective evidence from a number of studies suggests that the bilingual experience improves the brain’s so-called executive function—a command system that directs the attention processes that we  use  for  planning,  solving  problems  and  performing  various  other  mentally  demanding  tasks. These processes include ignoring distractions to stay focused, switching attention willfully from one thing to another and holding information in mind, like remembering a sequence of directions while driving.

    And the key difference between b