Scientists explain why people experience déjà vu
For some people, déjà vu is a supernatural phenomenon, while others explain it by neurological causes. DW conducted a study of this scientific phenomenon to understand it.
Have you ever felt that you are familiar with a certain situation? Have you ever had the impression that you've been somewhere before? If so, it could be déjà vu. Have you ever moved to a new city and everything there seemed very familiar? Have you ever met someone and felt like you had seen them before? If these situations are familiar to you, then you are one of those who have experienced déjà vu.
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The phrase "Déjà-vu", meaning "already seen", was coined by the French philosopher and researcher Emile Boarak in 1876. But scientists had been trying to unravel this phenomenon long before that. For example, the ancient Greek philosopher Plato believed that it was evidence of past lives.
Psychoanalyst Sigmund Freud described déjà vu as a memory of an unconscious fantasy that aims to improve the current situation. Psychiatrist Carl Jung saw it as a manifestation of the collective subconscious, and in Hollywood movies, déjà vu is often portrayed as an "error in the matrix."
However, neuroscience professor James J. Giordano of Georgetown Catholic Private University in Washington, D.C., believes that this phenomenon has nothing to do with supernatural events. According to him, déjà vu is a completely normal phenomenon when one feels that actions, thoughts and feelings have already been experienced before, although in fact they have not.
About 90 percent of the world's population has experienced deja vu at least once. But this phenomenon has one peculiarity: it becomes less common with age.
Why do you experience deja vu?
"In fact, there are no specific reasons for deja vu. Our brain works like a time machine in space. It takes our current experiences and combines them with similar or dissimilar experiences from the past. This allows our brain to plan for the future. However, sometimes these signals can get confused in our imagination," explains Prof. Giordano.
According to Giordano, this phenomenon occurs in the thalamus, located in the central part of the brain. All incoming signals from hearing, taste, and touch pass through the thalamus before reaching the outer layer, the cerebral cortex, where they are further processed and interpreted.
"If the speeds of these different interactions are unequal, our perception of the present may seem like a memory. Thus, our brains can sometimes confuse the present with the past," Giordano explains.
Roderick Spears, an associate professor of migraine research and clinical trials at Brown University in Providence, Rhode Island, also agrees that there is no clear explanation for why and how deja vu occurs. It is difficult for scientists to find out without concrete and tangible material.
How often does déjà vu occur?
"It is very difficult to observe deja vu because it occurs spontaneously. We don't know exactly how we can induce such episodes in a controlled laboratory environment," admits Roderick Spears.
One of the popular theories coming out of neuroscience is the concept of dual neurological processing, where information is processed and extracted in the brain through two different processes.
For example, you are sitting in your living room reading this article. You can smell dinner coming from the kitchen, your cat is next to you in a comfortable position in the basket, your cell phone is signaling a new message, and you can feel the warmth of the sun on your skin. All of these different impressions and perceptions are combined together in the brain during processing and interpreted as one overall experience.
According to this theory, if the brain processes this input with a slight delay, it can perceive this experience as two consecutive events and create a sense of familiarity with one of them from your past.
Theoretical physicist Michio Kaku believes that déjà vu is a memory disorder that occurs when "fragments of memories stored in the brain are brought out when we find ourselves in an environment that reminds us of previous events." The scientist is also exploring the theory of the possibility of transitioning between parallel universes and whether déjà vu can indicate our position and feelings in such universes.
Other studies show that stress can affect the occurrence of déjà vu.
"The brain functions better when it is rested and has enough energy. When we are under a lot of stress or anxiety, the brain can become tired, and this can lead to changes in our brain activity," explains Giordano.
Spears also adds that people with a high level of education are more likely to experience déjà vu than those with less education: "People who are committed and travel a lot may be better able to remember their dreams and experience déjà vu more often."
Is déjà vu a sign of a mental disorder?
"Not at all," Jordan assures us, "perfectly healthy people can sometimes experience déjà vu. This usually happens between the ages of 15 and 25.
Nevertheless, Spears recommends that people who experience déjà vu very often, for example, several times a month, seek medical help. Also, if déjà vu occurs along with a loss of consciousness or an unexpected dream-like state, it may indicate a more serious health problem.
In some cases, déjà vu can be a sign of an atypical epileptic seizure. "Most seizures occur in the temporal lobe of the brain when it is overstimulated and the person remains semi-conscious but does not lose consciousness completely. This can also lead to a feeling of déjà vu," explains Roderick Spears.
In general, there is a broad consensus on what déjà vu is and what can cause it. However, Spears complains: "Unfortunately, we do not yet have a reliable structural explanation for this phenomenon."
As a reminder, scientists have answered which asteroids can destroy the Earth and when it might happen.
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