"Deja vu" experiences

Originally Published: March 14, 2008 - Last Updated / Reviewed On: July 18, 2011
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Dear Alice,

Sometimes I experience instances in my life which I THINK I have encountered or experienced before, usually because the sights and/or sounds of the "deja vu moment" are familiar, or make me feel as if it is in my memory somewhere as the exact same sequence has occurred before.

How can these "deja vu instances" be explained? Is there a simple cognitive explanation behind this, or is it physics-related (i.e. belief in a parallel universe or some other theory that the future has actually happened already)?

I realize that many of my friends also experience this same kind of thing. Is it therefore a phenomenon that every human being will encounter?

Thank you,

Dear Pinkie,

It seems this has been asked before… (just kidding). Déjà vu, that feeling that you've been somewhere or seen something before, has intrigued people for centuries, yet it is not well understood. The term déjà vu literally means already seen, but has come to mean already experienced or already been as well. Many people (about 60 percent) experience déjà vu at some point in their lives, but some theorists suggest the people are more likely to experience this feeling if:

  • They are very imaginative.
  • They remember their dreams.
  • They are tired or stressed.
  • They have a high level of education.
  • They are open-minded.
  • They are between 15 and 25.

Déjà vu is often confused with pre-cognitive experiences — feelings that you know what is going to come next. Hallucinations and false memories are also confused with déjà vu, but true déjà vu occurs during an event and lasts for only about 10 to 30 seconds. Theorists separate déjà vu into two types:

  • Associative Déjà vu: this is the most common type of déjà vu and is believed to be caused by experiencing (seeing, smelling, hearing, feeling) something that you associate with something else in your past experiences. Researchers think this type of déjà vu is memory based.
  • Biological Déjà vu: this type of déjà vu is related to a condition such as epilepsy, and is thought to be caused by biological signals in the brain.

Déjà vu is sensation that is yet to be understood by science, even though so many people have reported experiencing déjà vu. There are a number of theories as to what causes déjà vu, but because it is difficult to study, researchers don't know for sure. The general consensus is that it is a cognitive sensation, not related to physics or a parallel universe. Theorists suggest it may be caused by issues with memory retrieval or delayed neurological responses. Further research into this topic may continue, but a definitive answer may never be found. In the words of Lao Tzu, "Such is the essential mystery."