A research team may have finally uncovered the cause of déjà vu.

If you’re feeling like you’ve read that headline before, well, that’s certainly possible. For decades, scientists have speculated about déjà vu, which occurs when a person errantly feels as if they remember a specific event or situation.

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Previously, scientists believed that the phenomenon occurred when the brain creates false memories. However, the new study suggests that déjà vu occurs when the brain checks to make sure a memory is legitimate. While that might sound like a small difference, it drastically changes our understanding of the neurology behind the feeling.

To perform the research, scientists found a way to trigger déjà vu.

A research team, led by Akira O’Connor at the University of St. Andrews in the United Kingdom, presented study participants with a purposely confusing experiment, then monitored the brains of study participants.

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University of St. Andrews

To create feelings of déjà vu, the team told each participant a list of related words, but not the keyword linking those words together. For instance, the word group “bed, pillow, mattress” wouldn’t contain the word “sleep.”

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Researchers then asked if the participants had heard words beginning with the letter “s.” Later, researchers would directly ask participants if they’d heard the word “sleep,” implanting the sense of déjà vu; while the participants knew that they hadn’t heard the word, they experienced a strange sense of recognition when prompted.

The researchers discovered that the frontal areas of the brain create the sensation.

These parts of the brain are strongly associated with decision making, rather than memory creation, which is mostly confined to the hippocampus; that’s a crucial distinction since it seems to indicate that déjà vu is a normal, predictable process.

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In other words, when the brain experiences the phenomenon, it’s simply deciding whether to trust a memory. Déjà vu is fairly common so that analysis makes sense; according to most research, about two-thirds of human adults have experienced the feeling at least once in their lives.

Still, déjà vu isn’t necessarily a symptom of a healthy brain.

Some injuries can stimulate the sensation. In one notable case, a patient’s dementia caused perpetual déjà vu (technically, déjà vécu, since “déjà vu” translates to “already seen” in French, while déjà vécu translates to “already lived”).

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The Faculties

“His wife said that he was someone who felt as though everything in his life had happened before,” Professor Chris Moulin of the Laboratoire de Psychologie et NeuroCognition CNRS in Grenoble told Quartz Media. “[She] would ask him how he could know what would happen in a television programme if he’d never seen it before, to which he would respond, ‘How would I know? I have a memory problem.’”

Still, it’s an exciting start—even if the findings do seem oddly familiar.

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