After 150 years of mystery, neuroscience has finally cracked the code on how language works in the brain—and the answer is surprisingly elegant.

Imagine you're watching a movie, in which a character puts a chocolate bar in a box, closes the box and leaves the room. Another person, also in the room, moves the bar from a box to a desk drawer.

One hesitation I hear time and time again when I talk to people about traveling is, “But I don’t speak the language.” To be ...