What Causes DéjàVu Science Behind the Eerie Feeling

If you’ve ever had the feeling that a situation feels very familiar even though you know it shouldn’t feel familiar at all, like if you’re traveling in a city for the very first time, then you’ve probably experienced dà ©jà   vu. Dà ©jà   vu, which means â€Å"already seen† in French, combines objective unfamiliarity – that you know, based on ample evidence, that something shouldn’t be familiar – with subjective familiarity – that feeling that it’s familiar anyway. Dà ©jà   vu is common. According to a paper published in 2004, more than 50 surveys on dà ©jà   vu suggested that about two-thirds of individuals have experienced it at least once in their lifetime, with many reporting multiple experiences. This reported number also appears to be growing as people become more aware of what dà ©jà   vu is. Most often, dà ©jà   vu is described in terms of what you see, but it’s not specific to vision and even people who were born blind can experience it. Measuring Dj Vu Dà ©jà   vu is difficult to study in the laboratory because it is a fleeting experience, and also because there is no clearly identifiable trigger for it. Nevertheless, researchers have used several tools to study the phenomenon, based on the hypotheses they’ve put forward. Researchers may survey participants; study possibly related processes, especially those involved in memory; or design other experiments to probe dà ©jà   vu. Because dà ©jà   vu is hard to measure, researchers have postulated many explanations for how it works. Below are several of the more prominent hypotheses. Memory Explanations Memory explanations of dà ©jà   vu are based on the idea that you have previously experienced a situation, or something very much like it, but you don’t consciously remember that you have. Instead, you remember it unconsciously, which is why it feels familiar even though you don’t know why. Single element familiarity The single element familiarity hypothesis suggests you experience dà ©jà   vu if one element of the scene is familiar to you but you don’t consciously recognize it because it’s in a different setting, like if you see your barber out on the street. Your brain still finds your barber familiar even if you don’t recognize them, and generalizes that feeling of familiarity to the entire scene. Other researchers have extended this hypothesis to multiple elements as well. Gestalt familiarity The gestalt familiarity hypothesis focuses on how items are organized in a scene and how dà ©jà   vu occurs when you experience something with a similar layout. For example, you may not have seen your friend’s painting in their living room before, but maybe you’ve seen a room that’s laid out like your friend’s living room – a painting hanging over the sofa, across from a bookcase. Since you can’t recall the other room, you experience dà ©jà   vu. One advantage to the gestalt similarity hypothesis is that it can be more directly tested. In one study, participants looked at rooms in virtual reality, then were asked how familiar a new room was and whether they felt they were experiencing dà ©jà   vu. The researchers found that study participants who couldn’t recall the old rooms tended to think a new room was familiar, and that they were experiencing dà ©jà   vu, if the new room resembled old ones. Furthermore, the more similar the new room was to an old room, the higher these ratings were. Neurological Explanations Spontaneous brain activity Some explanations posit that  dà ©jà   vu is experienced when there is spontaneous brain activity unrelated to what you’re currently experiencing. When that happens in the part of your brain dealing with memory, you can have a false feeling of familiarity. Some evidence comes from individuals with temporal lobe epilepsy, when abnormal electrical activity occurs in the part of the brain dealing with memory. When the brains of these patients are electrically stimulated as part of a pre-surgery evaluation, they may experience dà ©jà   vu. One researcher  suggests that you experience dà ©jà   vu when the parahippocampal system, which helps identify something as familiar, randomly misfires and makes you think something is familiar when it shouldn’t.   Others have said that dà ©jà   vu can’t be isolated to a single familiarity system, but rather involves multiple structures involved in memory and the connections between them. Neural transmission speed Other hypotheses are based on how fast information travels through your brain. Different areas of your brain transmit information to â€Å"higher order† areas that combine the information together to help you make sense of the world. If this complex process is disrupted in any way – perhaps one part sends something more slowly or more quickly than it usually does – then your brain interprets your surroundings incorrectly. Which Explanation is Correct? An explanation for dà ©jà   vu remains elusive, though the hypotheses above appear to have one common thread: a temporary error in cognitive processing. For now, scientists can continue to design experiments that more directly probe the nature of dà ©jà   vu, to be more certain of the correct explanation. Sources Tip-of-the-tongue states and related phenomena. Ed. Bennett L. Schwartz and Alan S. Brown. Cambridge University Press. New York, NY 2014. http://www.cambridge.org/gb/academic/subjects/psychology/biological-psychology/tip-tongue-states-and-related-phenomena?formatHBC. Moulin. The cognitive neuropsychology of dà ©jà   vu. Part of the Essays in Cognitive Psychology series. Psychology Press. New York, NY 2018. https://www.routledge.com/The-Cognitive-Neuropsychology-of-Deja-Vu/Moulin/p/book/9781138696266Bartolomei, F., Barbeau, E., Gavaret, M., Guye, M., McGonigal, A., Rà ©gis, J., and P. Chauvel. â€Å"Cortical stimulation study of the role of rhinal cortex in dà ©jà   vu and reminiscence of memories.† Neurology, vol. 63, no. 5, Sept. 2004, pp. 858-864, doi:10.1212/01.wnl.0000137037.56916.3f.J. Spatt. â€Å"Dà ©jà   vu: possible parahippocampal mechanisms.† The Journal of Neuropsychiatry Clinical Neurosciences, vol. 14, no. 1, 2002, pp. 6-10, doi:10.1176/jnp.14.1.6. Cleary, A. M., Brown, A. S., Sawyer, B.D., Nomi, J.S., Ajoku, A.C., and A. J. Ryals. â€Å"Familiarity from the configuration of objects in 3-dimensional space and its relation to dà ©jà   vu: a virtual reality investigation.† Consciousness and Cognition, vol. 21, no. 2, 2012, pp. 969-975, doi:10.1016/j.concog.2011.12.010.A. S. Brown. The dà ©jà   vu experience. Part of the Essays in Cognitive Psychology series. Psychology Press. New York, NY 2004. https://www.routledge.com/The-Deja-Vu-Experience/Brown/p/book/9780203485446A. S. Brown. â€Å"A review of the dà ©jà   vu experience.† Psychology Bulletin, vol. 129, no. 3, 2003, pp. 394-413. doi:10.1037/0033-2909.129.3.394.Bartolomei, F., Barbeau, E. J., Nguyen, T., McGonigal, A., Rà ©gis, J., Chauvel, P., and F. Wendling. â€Å"Rhinal-hippocampal interactions during dà ©jà   vu.† Clinical Neurophysiology, vol. 123, no. 3, March 2012, pp. 489-495. doi:10.1016/j.clinph.2011.08.012