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Déjà vu refers to the feeling that you have already experienced your present situation. It is remarkably common, with two out of three people—both men and women—experiencing the phenomenon at some point in their lives. Further, in those who experience déjà vu, the phenomenon happens about once per year, although its frequency decreases with age.
Despite déjà vu being relatively common, relatively limited research has been done on the subject. What we know so far is that in people without psychosis or temporal lobe epilepsy, the causes of déjà vu fall into four categories—attentional, memory, dual processing, and neurological.
- Attentional explanations of déjà vu involve an initial perception that is made under degraded attention, which is then followed by a second take under full attention. For example, if you are about to unlock the front door of your house, and you’re momentarily distracted by a noise in the distance, when you return to the task of unlocking the door, the first perception may seem further off in the past. The distraction that separates these two perceptions could be as fleeting as an eye blink.
- Memory explanations make the assumption that some detail of the new experience is familiar but the source of this familiarity has been forgotten. The premise of this explanation is that people encounter countless things during the course of a day but don’t pay attention to all of the information. Later reprocessing of the information may occasionally induce familiarity and déjà vu.
- Dual-processing explanations of déjà vu suggest that two usually synchronous cognitive processes become momentarily asynchronous. For example, familiarity and retrieval could become out of sync. Alternatively, perception and memory could become asynchronous.
- Neurological explanations of déjà vu attribute the phenomenon to either a small temporal lobe seizure in a person without epilepsy, or to a delay in neuronal transmission between the eyes, ears, or other perceptual organs and higher-order processing centers in the brain.
Dual-processing explanations have received a lot of attention—they are much more philosophical and theoretical, and less mechanistic, but dual-processing explanations can’t be tested in a lab. Similarly, neurological explanations are appealing in their neurological basis and seem logical, but again, we lack the advanced technology to test them. Thus, dual-processing and neurological explanations are less germane to researchers. Instead, attentional and memory explanations are best supported by what we know about cognition and can be empirically tested.
