Déjà Vu
From Physis to Physics
Déjà Vu: The Science Behind the Eerie Feeling of Familiarity
If you've ever experienced the sensation of familiarity in a place you've never been before, like feeling a sense of recognition in a city you're visiting for the first time, then you've likely experienced déjà vu. The term, which translates to "already seen" in French, encapsulates the strange mix of objective unfamiliarity - the logical understanding that something should not be familiar - with subjective familiarity - the inexplicable sense of familiarity nonetheless.
Déjà vu is a fairly common occurrence. A 2004 study suggested that approximately two-thirds of individuals reported experiencing déjà vu at least once in their lifetime, with many stating multiple experiences. The reported number seems to be on the rise as public understanding of the phenomenon increases.
Déjà vu is often associated with visual experiences but is not exclusive to them. Even people who are blind from birth can experience this phenomenon.
Single Element Familiarity This hypothesis suggests that déjà vu arises when an element in a scene is familiar, but not consciously recognized due to its context, such as seeing your barber in an unexpected location. While you may not consciously identify them, your brain recognizes the familiarity, extending it to the entire scene. This hypothesis has been extended to multiple elements within a scene as well.
Understanding Déjà Vu
Studying déjà vu poses significant challenges as it is a fleeting experience, and there isn't a clear trigger that induces it. Nevertheless, researchers have utilized several techniques based on varying hypotheses to understand the phenomenon. These methodologies range from participant surveys to studying associated memory processes, and other experimental designs to probe the occurrence of déjà vu. Due to the inherent complexities in measuring déjà vu, researchers have proposed a variety of theories for how it manifests. Below are some of the most notable ones.Memory-Based Theories
These theories posit that déjà vu is a result of having previously experienced a situation, or something closely resembling it, without consciously remembering it. This unconscious memory is what triggers the sense of familiarity, despite a lack of understanding why.Single Element Familiarity This hypothesis suggests that déjà vu arises when an element in a scene is familiar, but not consciously recognized due to its context, such as seeing your barber in an unexpected location. While you may not consciously identify them, your brain recognizes the familiarity, extending it to the entire scene. This hypothesis has been extended to multiple elements within a scene as well.
Gestalt Familiarity
The gestalt familiarity theory suggests déjà vu arises from a similar arrangement of objects in a scene. For instance, you might not have seen a specific painting in a friend's living room before, but the room's layout mirrors one you've previously encountered. Since you cannot recall the previous room, you experience déjà vu. One of the merits of this hypothesis is its testability. In one study, participants were shown rooms in virtual reality. Those who couldn't recall the old rooms were likely to deem a new room as familiar and reported experiencing déjà vu, particularly if the new room shared similarities with the old ones.
Spontaneous Brain Activity Some theories suggest déjà vu results from spontaneous brain activity that is not related to your current experiences. This spontaneous activity in the memory-related regions of your brain can give rise to a false sense of familiarity. Evidence for this theory is derived from individuals with temporal lobe epilepsy. During the pre-surgery evaluation phase, electrical stimulation of patients' brains can trigger a déjà vu experience.
Neural Transmission Speed Other theories attribute déjà vu to the speed of information transmission within your brain. Disruptions in this process—such as one part transmitting information slower or faster than usual—can result in an incorrect interpretation of your surroundings.
Sources
Schwartz, B. L., & Brown, A. S. (Eds.). (2014). Tip-of-the-tongue states and related phenomena. Cambridge University Press. Moulin, C. (2018). The cognitive neuropsychology of déjà vu. Psychology Press.
Bartolomei, F., Barbeau, E., Gavaret, M., Guye, M., McGonigal, A., Régis, J., & Chauvel, P. (2004). Cortical stimulation study of the role of rhinal cortex in déjà vu and reminiscence of memories. Neurology, 63(5), 858-864.
The gestalt familiarity theory suggests déjà vu arises from a similar arrangement of objects in a scene. For instance, you might not have seen a specific painting in a friend's living room before, but the room's layout mirrors one you've previously encountered. Since you cannot recall the previous room, you experience déjà vu. One of the merits of this hypothesis is its testability. In one study, participants were shown rooms in virtual reality. Those who couldn't recall the old rooms were likely to deem a new room as familiar and reported experiencing déjà vu, particularly if the new room shared similarities with the old ones.
Neurological Theories
Spontaneous Brain Activity Some theories suggest déjà vu results from spontaneous brain activity that is not related to your current experiences. This spontaneous activity in the memory-related regions of your brain can give rise to a false sense of familiarity. Evidence for this theory is derived from individuals with temporal lobe epilepsy. During the pre-surgery evaluation phase, electrical stimulation of patients' brains can trigger a déjà vu experience.
Neural Transmission Speed Other theories attribute déjà vu to the speed of information transmission within your brain. Disruptions in this process—such as one part transmitting information slower or faster than usual—can result in an incorrect interpretation of your surroundings.
The Elusive Explanation
Despite various hypotheses, a definitive explanation for déjà vu remains out of reach. However, the common thread across these theories is a temporary glitch in cognitive processing. As research continues, more specific experiments probing the nature of déjà vu may eventually lead to a more concrete explanation.Sources
Schwartz, B. L., & Brown, A. S. (Eds.). (2014). Tip-of-the-tongue states and related phenomena. Cambridge University Press. Moulin, C. (2018). The cognitive neuropsychology of déjà vu. Psychology Press.
Bartolomei, F., Barbeau, E., Gavaret, M., Guye, M., McGonigal, A., Régis, J., & Chauvel, P. (2004). Cortical stimulation study of the role of rhinal cortex in déjà vu and reminiscence of memories. Neurology, 63(5), 858-864.
Ali Reza Rashidi
Ali Reza Rashidi, a BI analyst with over nine years of experience, He is the author of three books that delve into the world of data and management.
