How It Works

What is Déjà vu?

Déjà vu is French for ‘already seen’. It describes the sensation many of us experience from time to time when we are sure a certain situation has happened before. It could be visiting a place you’ve never been but getting a feeling that it’s very familiar or having a conversation that you feel like you’ve had before, even down to the minute details of the clothes they are wearing and their position with respect to you.

There is no definite answer as to why déjà vu happens as there is no easy way to induce the sensation in a laboratory, therefore it is a difficult subject to study. One theory is that it happens due to a mismatch in the brain mistaking the present for the past. It is worth noting that the déjà vu feeling commonly precedes temporal lobe epilepsy attacks and has also been found to be common in patients with certain psychiatric conditions.

Déjà vu can be commonly confused with a similar sensation, which we may feel if a similar situation has happened before but has been forgotten. Our brains are full of forgotten memories that have slipped into our subconscious for whatever reason. The brain is always trying to find patterns so it may link a new experience with a similar forgotten memory creating the eerie sensation that you have ‘been there’ or ‘done that’ before when you actually have, and just forgotten.

Author: Rik Sargent, Science Museum