Whats Deja Vu

By Ian Lecklitner

If you’re a long-time member of the Club, you may have experienced a bout of déjà vu while reading through the July Bathroom Minutes magazine. More specifically, the “Name That Firework” feature probably left you thinking, “Have I seen this before?” And rightfully so. We did, in fact, print a similar guide to firework geometry two years ago. Which got us thinking: “What is déjà vu, anyway?” Fortunately, neurological researchers have tackled that very question with mind-boggling results.

If you’re a long-time member of the Club, you may have experienced a bout of déjà vu…

Okay, now we’re just messing with you. Let’s explore how your brain make memories and how a “glitch” in that system causes the feeling that we call déjà vu.

The first thing you should know is that research shows that you have two types of memories: 1) memories of things that have actually happened; and 2) memories of where and under which conditions those things happened. The latter are called source memories.

What is exactly is a source memory? Say you step into a bar that has the same layout and same bar stools as your favorite bar back home—this new bar might feel familiar because you’re so acquainted with those conditions, but you’ve never actually been there. It’s those memories—source memories—that lay the basis for déjà vu.

A 2009 study in the Psychonomic Bulletin and Review does an even better job of explaining source memories. In it, researchers had test subjects study various drawings of scenes. Later, they were given completely new scenes and asked if they had seen them before. The new scenes had similar layouts to the first round, but the actual objects within them were different. For instance, the subjects might have been shown a picture of a dog sitting between a building and a parked SUV followed by an image of a dog sitting between a palm tree and a city bus. Even though the two images were different, the subjects usually reported feeling as if they’d already seen the new one.

It’s situations like those—where your mind tricks you into thinking you have the source memory, but doesn’t contain the actual memory—that lead to feeling like you’ve been somewhere or seen something without knowing whether you really have or not, a.k.a. déjà vu.