Dear Lifehacker, I've been experiencing deja vu more often lately — you know, that odd feeling where you can swear you've been somewhere before or had the same conversation with someone but really didn't. Is this bad? Should I be concerned? My friend says she used to get it a lot but hasn't for years. Should she be concerned? Is this just a glitch in the Matrix? Thanks, Seeing Glitches
Image: Modified from istolethetv.
Déjà vu really is an uncanny feeling. The term in French literally means "already seen" and that's exactly why it's so unnerving: It really feels like you've already experienced a very specific event or been somewhere, even though you haven't (or, at least, you don't think so).
Further complicating the matter, there's no consensus yet on what exactly causes this phenomenon, though there are a lot of theories. Psychology Today points out a study that suggests that deja vu is just an extreme reaction of your brain's memory system when encountering things with lots of familiar objects just set up a little differently (for example, when you're in a restaurant configured almost identically to one you've been in before, you can get a powerful feeling of familiarity).
Scientists have found a possible cause for deja vu occurances in the brain. Popsci reports that mice lacking some specific receptors in the hippocampus area of the brain have responses similar to deja vu, so the theory is that deja vu can be just a temporary disorientation in the hippocampus, which is the part of the brain responsible for sense of direction and forming new memories.
To answer your questions, though, deja vu appears to be harmless for most people (as much as 70 per cent of the population has reported experiencing it, according to Discovery's How Stuff Works), with higher rates of occurence in people age 15 to 25 — so your friend's decreased deja vu experiences should be fine, too.
However... deja vu has also been associated with temporal-lobe epilepsy (one story shows a woman who had 20 years of deja vu episodes before finding out she had epilepsy). So, not to alarm you, but if you experience frequent déjà vu, you may want to see a doctor.
Finally, have you been feeling anxious or stressed out lately? Wikipedia mentions a link between deja vu and anxiety and you'll find lots of stressed-out people on health forums who also say they've been experiencing more deja vu. So our Lifehacker tip for trying to stop deja vu from happening, if you want to, is good old stress and anxiety reduction.
Got your own question you want to put to Lifehacker? Send an email to [email protected], and include 'Ask Lifehacker' in the subject line.