normal or symptom of a disease?
Research shows that most of us experience a feeling of déjà vu at some point in our lives. A sudden and inexplicable feeling that you have already been here, done and said the same thing. But you know for sure that this is impossible, because you have never been in this place, with these people, or engaged in this specific activity before. The experience of déjà vu occurs when a person feels that a situation is familiar, despite the fact that it is his first time in it.
Currently, there is a growing interest among cognitive researchers in understanding the nature of déjà vu. In the article we will consider the phenomenon, the main theories of its occurrence and differences from pathology.
Introduction
What is deja vu
The term deja vu comes from two French words deja vu, which translates as “already seen.”
The first to mention this word was in 1876 the philosopher Emil Boirak in a letter to the editor of the Philosophical Review when describing his own experiences. In 1983, Dr. Vernon Neppe formulated a definition of the phenomenon in his book The Psychology of Déjà Vu. The definition he gave is still considered generally accepted in scientific circles.
Déjà vu is “any subjective, inappropriate feeling that a present experience is like an uncertain past.”
Research confirms that illusion is not associated with significant events or strong emotions. It can occur at any time and does not depend on external circumstances. In this case, not vague feelings appear, but quite specific ones. Doctor of Medical Sciences Joseph Spatt noted that the subjects used the words “exactly” and “down to the smallest detail” to define their sensations. The scene or episode was perceived as vividly as when they seemingly first met. The phenomenon was described as a photographic copy of an alleged past experience.
However, psychologist D. L. Schacter, in an article on illusory memories, noted that déjà vu is always accompanied by a feeling of inappropriateness and unreality of this feeling. This is the main difference between the phenomenon and hallucinations and “false memories.”
The state of deja vu is accompanied by a feeling when you know exactly the further direction of movement, the sequence of events and phrases. But, according to research, such a premonition in most cases can be illusory. The only exceptions are those situations when past experience was forgotten or was learned unconsciously.
There are criteria for determining deja vu:
the transfer of familiar situations to new ones is not realized and occurs under the condition of their visual or semantic similarity;
the feeling of recognition is irrational, this cannot happen in reality;
the emergence of internal conflict and understanding of the unreality of what is happening.
Most people experience déjà vu from time to time. The phenomenon is reflected in fiction and cinema. It evokes powerful images and resonates with readers and viewers because so many of us have experienced it.
However, research confirms that as people age, they experience this feeling less and less often. The degree of manifestation directly depends on the socio-economic level of human development. Young people are often overloaded with problems in their personal lives, studies and work, which leads to fatigue, stress and constant sleepiness. As a result, the efficiency of the cognitive functions of the brain decreases. At the same time, the feeling of déjà vu occurs with equal frequency in both men and women.
Types of deja vu
V. Neppe described more than 20 varieties of experiencing the feeling of deja “already.” The most common ones are:
déjà lu – already read;
déjà parlé – already discussed;
déjà visité already visited a locality – already visited locality;
déjà rencontré already met – have already met this person;
déjà raconté already recounted already told – already told;
déjà arrive already happened – what has already happened;
déjà vu already seen – already seen.
Less common are the following varieties: already heard, felt, done, sensed through smell, tasted, repetition of a thought, etc.
Separately, the opposite of deja vu is distinguished – jamais vu – “never seen”.
Jamet vu is a feeling in which an objectively familiar situation seems unknown. For example, when you come to your home and for a moment it seems that you don’t know the situation around you.
Esotericism and attempts to explain déjà vu
They try to explain deja vu with esoteric teachings – mystical ways of perceiving reality. Let’s look at the most popular of them.
Reincarnation
At the heart of this explanation is the assumption of the existence of reincarnation. A person is not living his first life, so déjà vu is interpreted as memories from previous incarnations. The phenomenon manifests itself when a person is in situations similar to past lives.
Parallel Worlds
The illusion overcomes a person because at one moment he is in this situation in several parallel worlds. The sensation appears during their intersection. This phenomenon confirms the existence of parallel universes.
Matrix failure
Adherents of this theory believe that the real world is just a simulation. By analogy with the film “The Matrix,” people live in a simulation, and the world is ruled by machines. A feeling of déjà vu occurs when the system fails.
Clairvoyance
Deja vu is the result of a premonition of a similar situation in reality or in a dream. This also includes the so-called prophetic dreams. A person “sees” his future, after which a feeling of repetition of the situation arises.
Scientific theories and research
For more than a hundred years, researchers have offered many interpretations of the phenomenon. V. Neppe suggested that “one single explanation for déjà vu is probably as wrong as one single cause of headache.” Other researchers similarly believe that the reasons depend on the person and the situation and can even be different for the same person for different situations in which the phenomenon manifests itself.
Modern research includes two methods:
Observation. Helps to determine the characteristics of the experience of a sensation and find relationships in the results obtained, to find out who experiences it, with what frequency and at what moment.
Experiment. The presenters cause the phenomenon to manifest in people using an artificial laboratory method and study it during the experiment.
Early researchers relied on the assumption that déjà vu was a form of psychopathology. For example, Calkins suggested that the phenomenon is “accompanied by an experience characteristic of many forms of madness.” This approach has distorted the way of research in many projects, but has expanded knowledge on the connection of the phenomenon with various forms of pathology.
We have highlighted the most popular theories that have been supported by the scientific community and proven by researchers.
Pulse Rate Failure
The phenomenon may result from a transient change in the normal rate of neural transmission. The disorder causes a delay in the arrival or acceleration of synaptic transmission of information along one of the pathways. As a result, the brain processes the received data twice and a corresponding sensation appears.
This approach examines the phenomenon from a neurological point of view. This is a short-term dysfunction of the brain, which is accompanied by an acceleration or deceleration of the normal course of neural impulse transmission.
Episodic forgetting and memory blocking
Some situations or settings may be truly familiar, but the source of the familiarity is clearly not recalled. Déjà vu occurs as a result of unconscious remembering of the past in the present. In this case, the person cannot remember the source of the acquaintance at that very moment or the information is lost forever.
Deja vu is based on the fact that the situation has actually been experienced before, but the person cannot remember it. Some aspect of a situation is stored in long-term memory, and implicit recognition is associated with that piece of information from the past.
This may also include memories blocked due to severe emotional distress.
Re-perception
The theory is based on the fact that a person initially finds himself in a certain situation, but perceives it inattentively or in fragments. For example, he is distracted by conversations while walking around the city, but with his peripheral vision he notices a store on the other side of the street. At this time, the brain processes the incoming information. Taking a closer look at the store in this case will give you a feeling of déjà vu.
The phenomenon is based on duplication of perception. It assumes that initially a person perceived information with distraction to his thoughts or an external stimulus, but immediately after that he turned his attention to a new object. In this case, a double perception of information occurs and the impression is created that there is no connection between events.
Double processing
The explanation is based on the idea of temporary desynchronization of thought processes that usually occur in parallel. This disconnect occurs when one process is absent while another is active, or when the brain simultaneously remembers and retrieves information in memory.
An example would be an optical illusion. Looking at the picture and thinking at the same time gives the feeling that this situation has already been experienced before. Visual and mental processes occur in isolation from each other, and the cognitive mechanism in this case works in the background.
Completion of information
The phenomenon sometimes arises not as a result of forgetting, but as a result of an error in mental activity. Recollection of a situation may include a mixture of facts and speculation. This approach explains why young people with good memories are more likely to experience déjà vu.
Neuroscientist Akira O’Connor conducted an experiment using MRI scans of the brain. The subjects were offered a series of 15 words with similar meanings – “Bed”, “Pillow”, “Night”, “Rest”, etc. The contextual word “Sleep”, which connects all the others, was deliberately omitted. Then the experimenter asked if the participants remembered the word “Dream,” and the subjects felt a déjà vu effect. MRI scans showed that at this moment the medial prefrontal cortex, responsible for identifying conflicts, is activated. However, no connection was found between reports of déjà vu and areas transmitting memory signals.
According to this approach, the phenomenon occurs when the brain tries to correct inaccurate memories. Such memory errors are a natural result of the human intellectual system. When you see similar objects or episodes from the past, you may get the feeling that this has already happened.
Disruption of parts of the brain
The temporal lobe and hippocampus are important in remembering or retrieving information from memory, especially episodic and autobiographical memory.
The hippocampus is responsible for transferring information from short-term memory to long-term memory. He participates in the process of recognizing an object or situation. A violation can cause a person to perceive reality as something that has already happened sometime before. Déjà vu occurs when the size of the hippocampus decreases as a result of prolonged stress and exposure to the hormone cortisol.
The temporal lobe of the brain is also involved in the process of occurrence of the phenomenon. The phenomenon is associated with the appearance of spontaneous electrical impulses, increased excitability and even temporal lobe epilepsy, the focus of which is located precisely in this brain structure. The studies were carried out by electrically stimulating the brains of people with and without pathology. The results revealed that people with epilepsy are more likely to experience flashback-like experiences and hallucinations immediately before the attack itself.
The parahippocampus and neocortex are responsible for recognizing objects or events. Violations in them lead to the fact that a new situation may seem familiar.
Pathology or normal: source of the effect
Déjà vu often appears in a state of stress and fatigue, but can be a symptom of a disease and a signal to contact a specialist. Features such as the frequency of occurrence and duration of the sensation will help determine the nature of the phenomenon.
Consequence of overvoltage
Akira O’Connor believes that experiencing déjà vu once a month is the norm for a healthy person. With prolonged fatigue, stress and nervous overexcitation, it may appear more often, because neural processes can no longer recover on their own. It becomes difficult for a person to cope with familiar tasks, memory deteriorates, and delusions and hallucinations may appear.
People predisposed to epilepsy take longer to recover from prolonged fatigue. Drowsiness and headaches will haunt them for several days. At the same time, if a person feels well and has had enough sleep, latent epilepsy does not manifest itself in any way.
A harbinger of the disease
Identification of pathology is carried out individually, taking into account the frequency of occurrence, duration of déjà vu, and the presence of negative emotions before its appearance.
In 2012, scientists P. Vlasov and A. Chervyakov conducted a study on healthy people, as well as on patients with epilepsy and space-occupying brain tumors. They concluded that in healthy people, déjà vu occurs several times a year and lasts no more than 10 seconds. Patients with epilepsy experience this feeling both with and without a seizure. In people with brain tumors, it can occur up to several times a day, last more than one minute, and cause feelings of fear.
In addition to these diseases, the phenomenon can be a symptom of encephalopathy—dystrophic damage to brain tissue after infections, intoxications, or metabolic disorders.
The feeling of déjà vu is a common phenomenon that occurs in both pathological and non-pathological conditions. At the same time, a person is always aware of the impossibility of the fact that the present has already happened in the past.
Only further research will help assess the clinical and psychiatric significance of the experiences, as well as study their characteristics.
Do you know this feeling?
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