Déjà vu is a rare occurrence, but you know it when you feel it. As you walk through a new city for the first time, something familiar clicks in your mind, giving you pause. You’ve definitely been here before.
But you haven’t. So what gives?
Well, no one really knows for sure. The origin of déjà vu (French for “already seen”), a sense of familiarity with something entirely new, remains hidden somewhere deep in our brains. The phenomenon is difficult to study—most people, when they experience déjà vu, aren’t hooked up to a bunch of electrodes, with clipboard-toting researchers at the ready.
A second hypothesis involves another brain error; this time, the problem is with our memory, says Anne Cleary, a cognitive psychology professor at Colorado State University. Something about a new situation or setting activates a memory of a similar past experience, but our brains fail to recall it. Cleary offers this scenario to help explain: Imagine you’re visiting Paris for the first time, and you have arrived at the Louvre. Your gaze lands on the giant glass pyramid jutting out of the museum’s main courtyard, and you get that strange feeling.
Read the whole story: Smithsonian Magazine