Why we have Deja vu?

• Figure 1 - What is and what is not a déjà vu experience?
• A. We all go through our lives seeing and experiencing things that we may remember later on. Our memories typically work very well and we can usually trust the feelings of memory we experience. In this picture, you are watching a video of a monkey riding a goat for the first time so it feels like a funny, new thing. B. Sometimes we see and experience things that we recognize or that look like other things we have already seen. When this happens and our memories are working well, we may feel a sense of familiarity. This feeling is entirely appropriate and is not déjà vu. In this picture, you can see a man riding a horse who looks a bit like the monkey riding the goat that you just watched online. Although it is a coincidence that you have seen two such similar things, the feeling of familiarity is appropriate so the sensation you feel is not déjà vu. C. When something feels too familiar, whether it is a thing you recognize or not, and the familiarity feels wrong, you are probably having a déjà vu experience. You often notice this kind of over familiarity because the feeling happens very quickly and then also quickly fades to a normal level of familiarity. In this picture, you see horses and they suddenly feel familiar. You know that although you have seen horses before they should not make you feel as strongly familiar with them as these horses do. Then, the feeling fades away and you wonder what just happened. That is a déjà vu experience!

In this review, you will read about how often we experience déjà vu. You will then read about how researchers have investigated déjà vu and what they think might cause it.