Book Definition: The experience of feeling sure that one has witnessed or experienced a new situation previously (an individual feels as though an event has already happened or has happened in the recent past), although the exact circumstances of the previous encounter are uncertain.


There are many theories as to why this happens. The term is French, meaning "seen before". One is the idea that the mind "takes a break" for a second and the information being processed is not interpreted. Then, when you snap back, you continue observing and the events that occurred during the brain's break begin to be interpreted, making it seem as though what you are seeing has happened before. It could also happen due to not focusing too much the first time around; the new memory gets confused with the gap in the old memory, or the new memory collides with one that was deleted. Another theory is that the interpretation reaches the brain before the signal to make it a memory reaches the brain.

In Your Own Words

  • Experiencing an event that you feel has already happened.
  • Feeling sure that one has witnessed or experienced a new situation previously.
  • When you feel like you have already done what you are currently doing.
  • Our brains forming events as a memory faster than we are perceiving it.
  • In actuality, your mind is observing your surroundings faster than you are... so you feel like what's going on has already happened before but really your mind just took it in earlier than you would have thought.


  • Having a conversation with someone that you know you couldn't have had before, even though for a brief moment it may feel that it has happened identically in the past.
  • Standing in front of a theme park entrance that you're going to for the first time and feeling like you've been there before.
  • Hearing a new song that that you think you have heard before.
  • Going to sleep and dreaming of a scene, and then the next day you see that happen before your eyes. You get the sense that this has happened before or you have seen this before.
  • Watching a movie for the first time, but you swear you've seen that same movie before.
  • You are sitting in choir rehearsal and all the sudden you think to yourself, "Wait a second... we just did this song", and you actually didn't.
  • Hearing someone say a sentence during a conversation and immediately recognizing the situation, claiming it has happened before.
  • Thinking a conversation that is taking place right now has already happened and you're hearing the person's response for the second time.
  • Going to a new city and thinking you have been there before but you really have just thought or dreamt about it.
  • Doing homework from a new lesson that you've never done and thinking you have seen and done the homework before

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Additional Resources



  • Déjà vu is actually quite a common occurrence; about 60% of people have experienced the phenomenon. Déjà vu is thought to be elicited from stress and fatigue. It has been proven that as age increases, the frequency of occurrence decreases. Scientists have proven that déjà vu can be explained in four categories. 1) That two mental processes become temporarily out of synch (dual processing). 2) Disruption of neural transmitters, ex: seizure (neurological). 3) A familiar, unrecognized stimuli (memory). 4) Subconscious perception followed by a conscious perception (attentional). These studies were published by Alan S. Brown in 2003.
  • An experiment was done by Anne Cleary, Anthony Ryals, and Jason Nomi in December 2009 on the concept of Deja vu. In the experiment, people were given a number of drawings from scenes and were asked to study each drawing for a limited amount of time. Later, the same people were given a set of completely new scenes and were asked if they have seen the new scenes before. Even though all of the scenes were different from the original drawings they were asked to study, many people responded confidently saying they have seen some new scenes before. The new scenes had similar traits to the original drawings but none were identical. The person who responded that they had seen the new drawings before experienced deja vu and really only saw very similar drawings. In conclusion, the experience of déjà vu is just an extreme reaction of the system that your memory uses to tell you that you are in a familiar situation.