The science of deja vu: Have you read this before?

Discover the science of déjà vu and the technique used to trigger it

Around 70 per cent of us experience it, in particular those of us aged 15–25, and it can be one of the most jarring feelings: déjà vu. French for ‘already seen’, it has previously been linked to the theory of false memories; the idea that we can view something once and when exposed to a scene or situation that is similar our brain will respond by creating a memory that didn’t really happen. However, an experiment led by psychology researcher Akira O’Connor in 2016 revealed that this might not be the case. Rather than false memory, the brain is memory checking and sending an error message, signalling what we have actually experienced versus what we think we have experienced. Around 70 per cent of us experience…wait a minute…

O’Connor’s experiment:

How did scientists artificially trigger déjà vu in the study’s volunteers?

Step 1

Participants were given a list of words to remember including bed, pillow, dream and doze; all words that are connected, in this case, to the word ‘sleep’.


Step 2 

They were then asked if any of the words began with the letter ‘S’. Of course, each person said no.


Step 3

Later on, the volunteers were asked if the word ‘sleep’ was included in the previous list of words. This prompted a feeling of déjà vu.


Step 4

Those experiencing the chilling phenomena were scanned using functional magnetic resonance imaging (fMRI) to identify the active parts of their brain.


Step 5

Scans revealed that the memory centre of the brain, the hippocampus, was unexpectedly not active, but the frontal areas that handle decision-making were active instead.

This article was originally published in How It Works issue 110

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