We’ve all experienced the feeling of having lived the same moment before. Scientists now claim to have found an explanation for the phenomenon.
Feel like you’ve been here before?
Feel like you’ve heard this story before?
Feel like you’ve had this exact same experience before?
Déjà vu is a well-known and wide-spread phenomenon. At least two thirds of people experience it at some point in their lives. However, until recently comparatively little was known about what triggered this fleeting sensation of reliving something that never happened.
Déjà vu has traditionally been thought to be caused by false memories created by the brain. But now, the first study into the phenomenon using magnetic resonance imaging scans seems to disprove this hypothesis. The findings of the new study suggest that our brain in actually checking its memory bank, just like we do when we search through an image file on our PC to find a specific photo.
A team from the University of St Andrews in Scotland, led by psychologist Akira O’Connor, has studied the phenomenon in a lab. Researchers used a standard method for triggering false memories. This involved telling the volunteer a list of related words – such as bed, pillow, night, dream, and so on – without mentioning the word that connects them all: in this case, sleep. When the person is later quizzed on the words they heard, they tend to think they heard ‘sleep’ too.
That’s how to implant a false memory, but it’s not quite déjà vu. To achieve that, researchers added an extra step to the experiment. First, they read the volunteers the list of words outlined above – skipping the obvious linking word: ‘sleep’. Then they asked them if they’d heard any word beginning with the letter ‘s’. Participants replied that they hadn’t. Afterwards, participants were asked if they’d heard the word ‘sleep’. Because of the previous question, they were able to remember that they hadn’t. And yet, at the same time, the word sounded familiar to them. ‘They reported having this strange experience of déjà vu,’ explained O’Connor.
While volunteers experienced this sensation, O’Connor’s team used fMRI to scan their brains. Rather than the areas of the brain involved in the memory, like the hippocampus, becoming active – as might be expected – researchers discovered that the frontal areas of the brain were active instead.
O’Connor and his team posit that what happens to the brain during déjà vu is really a process of decision making or conflict resolution. The brain is engaged in a process of fact checking – checking through its database, just as we might verify data on a computer, and sending signals when it encounters an error, a conflict between what we’ve actually experienced and what we think we’ve experienced.
Researchers suggest that déjà vu could be a sign that your brain’s checking system is working well. This could also explain why déjà vu is experienced more frequently by young people and trails off as memory deteriorates in old age.
The findings of the study are yet to be confirmed. Even so they bring a fresh perspective to a curious phenomenon that’s always been shrouded in mystery: déjà vu as a tool for fact checking the story of our life.