On a cold rainy day, I saw a girl in a white skirt with a red umbrella walking toward me. I was almost certain that she was going to stare me in the face and brush against me. And she really did. I screamed in silence and quickly checked calendar if that day is Friday the 13th.

It’s not. Lucky me. I told this story to people around me, to my surprise, many said they had experienced similar déjà vu and feelings of prediction before. If it is not supernatural, where do these feelings come from? Memory researcher Anne Cleary now has a theory to explain.
Déjà vu is a memory phenomenon
“Déjà vu” is a French term and literally means "already seen." It refers to the feeling that you have experienced a situation before even though you know you haven't.

You have this feeling because the thing at this moment reminds you of something similar happened before, but you can’t remember it very clearly. Déjà vu is not about supernatural, but about your memory.
In order to verify this theory, Cleary conducted a series of experiments.
How the study went

The research team created the participants a virtual world, which contains scenes like the video game The Sims.
First, the team asked if they were experiencing déjà vu. Then, they changed the scene and asked the participants if the scene changed in the way they expected. It turns out that the participants who were having déjà vu were not able to predict what was going to happen next.
When the participants saw something familiar and déjà vu occurred, they knew what particular thing was going to happen based on their memory. But the experiment didn’t follow the routine in the game. The changes were totally random. Surely people didn’t have the ability to predict random things.

So, the prediction due to déjà vu is not based on facts. Instead, it is based on memory and feeling. In other words, when I saw that girl in the white skirt, the reason why I successfully predicted her next move is because I remembered I saw a similar girl who did similar thing before. I didn’t predict depending on analysis or causality.
Cleary is now planning to further her study with neuroscientists, as déjà vu is a typical symptom of a type of seizure. Maybe in the future, the research on déjà vu can shed some light on medicine and human health.