Have you ever had that strange feeling that you’ve experienced the exact same situation before, even though that’s impossible?
Sometimes it can even feel like you are reliving something that has already happened. This phenomenon, known as déjà vu, has long puzzled philosophers, neuroscientists and writers.
Beginning in the late 1800s, many theories began to emerge about what might cause déjà vu, which means “already seen” in French.
People thought that maybe it came from a mental malfunction or maybe some type of brain problem. Or perhaps it was a temporary hiccup in the otherwise normal functioning of human memory. But the subject did not reach the realm of science until very recently.
Transition from the paranormal to the scientific
At the beginning of this millennium, a scientist named Alan Brown decided to review everything researchers had written about déjà vu up to that point.
Much of what he could find had a paranormal flavor, having to do with the supernatural – things like past lives or psychic abilities. But he also found studies that regularly surveyed people about their déjà vu experiences.
From all these documents, Brown was able to gather some key findings about the déjà vu phenomenon.
For example, Brown determined that about two-thirds of people experience déjà vu at some point in their lives. He determined that the most common trigger for déjà vu is a scene or place, and the next most common trigger is a conversation.
He also pointed to hints in nearly a century of medical literature of a possible association between déjà vu and certain types of epileptic activity in the brain.
Brown’s review brought the topic of déjà vu into the realm of more mainstream science because it appeared both in a scientific journal that cognitive scientists tend to read and in a book aimed at scientists. His work served as a catalyst for scientists to design experiments to investigate déjà vu.
Déjà vu test in the psychology lab
Prompted by Brown’s work, my own research group began conducting experiments aimed at testing hypotheses about possible mechanisms of déjà vu.
We investigated a nearly century-old hypothesis that déjà vu can occur when there is a spatial similarity between a current scene and a scene that is not recalled in your memory. Psychologists have called this the Gestalt intimacy hypothesis.
For example, imagine you pass the nursing station at a hospital unit on your way to visit a sick friend. Although you have never been to this hospital before, you are impressed with the feeling you get.
The root cause for this experience of déjà vu could be that the layout of the scene, including the placement of furniture and specific objects within the space, has the same layout as a different scene that you have experienced in the past.
Perhaps 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 welcome tables was placed 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 you don’t recall that previous situation with a similar layout to the current one, you may be left with only a strong sense of familiarity for the current one.
To explore this idea in the lab, my team used virtual reality to place people inside scenes. This way we could manipulate the environments people were in – some scenes shared the same spatial layout while others were distinct.
As predicted, déjà vu was more likely to occur when people were in a scene that contained the same spatial arrangement of elements as a previous scene they saw but did not remember.
This research suggests that a contributing factor to déjà vu may be the spatial similarity of a new scene to a scene in memory that fails to be consciously recalled at the moment.
However, it does not mean that spatial similarity is the only cause of déjà vu. Quite possibly, many factors can contribute to what makes a scene or situation feel familiar. More research is underway to investigate additional potential factors at play in this mysterious phenomenon.
Anna ClearyProfessor of Cognitive Psychology, Colorado State University
THis article is republished from The Conversation under a Creative Commons license. Read the original article.