Have you ever had this strange feeling of having experienced exactly the same situation before, even if it is impossible? Sometimes you may even feel like you are reliving something that has already happened. This phenomenon, known as deja vu, has long intrigued philosophers, neurologists and writers.
Beginning in the late 1800s, many theories began to emerge regarding what might cause deja vu, which means “already seen” in French. People thought maybe it was from mental dysfunction or maybe some type of brain problem. Or maybe it was a temporary hiccup in the otherwise normal functioning of human memory. But the subject did not reach the realm of science until recently.
From Paranormal to Scientific
At the beginning of this millennium, a scientist named Alan Brown decided to review everything that researchers had written about deja vu up to that point. Much of what he could find had a paranormal flavor to it, having to do with the supernatural – things like past lives or psychic abilities. But he also found studies that asked ordinary people about their experiences of deja vu. From all these articles, Brown was able to glean some fundamental discoveries about the deja vu phenomenon.
For example, Brown determined that about two-thirds of people experience deja vu at some point in their lives. He determined that the most common trigger for deja vu is a scene or place, and the second most common trigger is a conversation. He also reported clues throughout about a century of medical literature of a possible association between deja vu and certain types of seizure activity in the brain.
Brown’s review brought the subject of deja vu into the realm of more mainstream science, as it appeared both in a scientific journal that scientists who study cognition tend to read, and also in a book intended to scientists. His work served as a catalyst for scientists to design experiments to investigate deja vu.
Deja vu test in the psychology lab
Prompted by Brown’s work, my own research team began conducting experiments aimed at testing hypotheses about the possible mechanisms of deja vu. We investigated a nearly century-old hypothesis that deja vu can occur when there is a spatial resemblance between a current scene and a scene you don’t remember. Psychologists have called this the Gestalt familiarity hypothesis.
For example, imagine walking past the nursing station of a hospital unit on your way to visit a sick friend. Although you have never been to this hospital before, you are struck by the feeling you have. The underlying cause for this deja vu experience could be that the layout of the scene, including the placement of furniture and particular objects in the space, has the same layout as a different scene that you experienced in the past.
Maybe the way the nursing station is located – the furniture, the items on the counter, the way it connects to the corners of the hallway – is the same as how a set of reception tables has been arranged in relation to signs and furniture in a hallway at the entrance to a school event you attended a year earlier. According to the Gestalt familiarity hypothesis, if that previous situation with a disposition similar to the current situation does not come to mind, you may only be left with a strong sense of familiarity for the current situation.
To investigate this idea in the lab, my team used virtual reality to place people in scenes. This way we could manipulate the environments people were in – some scenes shared the same spatial layout yet were distinct. As expected, deja vu was more likely to occur when people were in a scene that contained the same spatial arrangement of elements as a previous scene that they had seen but did not remember.
This research suggests that a contributing factor to deja vu may be the spatial resemblance of a new scene to a scene in memory that is not consciously recalled at the time. However, that doesn’t mean that spatial resemblance is the only cause of deja vu. Most likely, many factors can contribute to making a scene or situation feel familiar. Further research is underway to investigate other possible factors at play in this mysterious phenomenon.
This article is republished from The Conversation under a Creative Commons license. Read the original article.
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