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Machines Like Us

What is déjà vu and why does it happen?

Friday, 11 January 2013
by Amy Reichelt

Credit: Wikimedia commons

Have you ever experienced a sudden feeling of familiarity while in a completely new place? Or the feeling you’ve had the exact same conversation with someone before?

This feeling of familiarity is, of course, known as déjà vu (a French term meaning “already seen”) and it’s reported to occur on an occasional basis in 60-80% of people. It’s an experience that’s almost always fleeting and it occurs at random.

So what is responsible for these feelings of familiarity?

Despite coverage in popular culture, experiences of déjà vu are poorly understood in scientific terms. Déjà vu occurs briefly, without warning and has no physical manifestations other than the announcement: “I just had déjà vu!”

Many researchers propose that the phenomenon is a memory-based experience and assume the memory centres of the brain are responsible for it.

Memory systems

The medial temporal lobes are vital for the retention of long-term memories of events and facts. Certain regions of the medial temporal lobes are important in the detection of familiarity, or recognition, as opposed to the detailed recollection of specific events.

It has been proposed that familiarity detection depends on rhinal cortex function, whereas detailed recollection is linked to the hippocampus.

The randomness of déjà vu experiences in healthy individuals makes it difficult to study in an empirical manner. Any such research is reliant on self-reporting from the people involved.