We think we’re experiencing the world as it is, but we’re not—it’s a virtual reality constructed inside our heads. Our brains are constantly making predictions about what’s out there. Our perceptions, then, are more about what the brain expects to encounter than what is truly there. What you think is what you see. Language creates expectations that influence our perception of the world more generally because we use language to think to ourselves.

Is the “bilingual advantage” real? Research suggests that people who speak two languages are more efficient in language processing and other tasks, and that speaking two languages from a very early age may keep the brain in good shape as we get older.

Of the estimated 7,000 languages spoken in the world today, nearly half are in danger of extinction and are likely to disappear in this century. In fact, they are now falling out of use at a rate of about one every two weeks. A key factor in language decline is that speakers and writers of the 83 languages with “global” influence now account for 80 percent of the world population. Most of the thousands of other languages now face extinction at a rate that exceeds that of birds, mammals, fish or plants. Projects like the Living Tongues Institute for Endangered Languages aim to identify and record endangered languages.

Learn more about how we have developed thousands of languages over the course of human history and how hundreds of new words come to be each year with these TED-Ed lessons.