by Lauren Lin
Déjà vu is the hard to describe and sometimes eerie feeling that you’ve already experienced something before, despite knowing that you’re in a new situation. For example, you could feel as though you’ve already watched a certain movie, even though you can’t remember when, and you objectively think that it should be the first time that you’ve seen it. Over the years, people have attributed this phenomenon to a variety of causes, ranging from reincarnation, to glitches in our memory, to supernatural theories.
While some of these explanations are interesting to think about, many lack scientific evidence. However, despite the numerous scientists who research déjà vu, there hasn’t been a theory that everyone can seem to agree on.
Some research has indicated that there may be a connection between our memory system and the feeling of déjà vu. Anne M. Cleary, a psychologist at Colorado State University, investigated the relationship between déjà vu and our recognition memory—the type of memory that alerts us that we have already experienced what we are currently going through. Recognition memory has two subdivisions: recollection and familiarity. Recollection-based recognition is when we can explicitly remember when in the past we have experienced something. For example, if you went and saw the new Star Wars movie for the second time, you’d experience recollection-based recognition because you would know that it’s your second time seeing the movie. Familiarity recognition is when we are less sure about why we seem to recognize a situation, which is why it is thought to be responsible for déjà vu. Cleary performed a series of experiments that induced déjà vu, and discovered that when small fragments of memories (such as geometric shapes) overlap with a new experience, it may create the false impression that you’ve seen or done something before.
On the other hand, Akira O’Connor and his research team at the University of St. Andrews used a word task to elicit déjà vu and to measure the brain activity of 21 volunteers using fMRI. O’Connor discovered that areas of the brain usually associated with memories were inactive during the test and that déjà vu may be mediated by frontal areas of the brain that play a role in decision making, which were active. Therefore, déjà vu may not be a consequence of poor memory. Rather, O’Connor hypothesized that déjà vu comes from the brain realizing that there has been a mistake in the recall process, and so it might signify that your memory checking system is functioning well. This is consistent with the fact that younger people experience déjà vu more frequently and that its occurrence decreases as age increases, since memory checking abilities deteriorate as people grow older.
A case that seems to be promising for further study is that of a 23-year-old British man who appears to have “chronic déjà vu.” The man reported that he felt as though he was reliving experiences for extended periods of time, and his condition became so disruptive that he stopped watching television, listening to the radio, and reading newspapers. He was otherwise healthy, and his brain scan results didn’t suggest any abnormalities, which led researchers to believe that his chronic déjà vu had a psychological cause. The man used to have depression and anxiety, but so far no conclusions can be made about the reason behind his condition. However, déjà vu has been found to be connected to certain psychoneurological disorders, like temporal lobe epilepsy. Those who have temporal lobe epilepsy tend to experience mood and memory difficulties and frequently experience déjà vu during aura (subjective perceptions that occur around the same time as seizures and sometimes serve as warning that a seizure is about to happen).
Researchers are working hard to gain a better understanding of déjà vu, but its cause remains elusive for now. Will we be able to find out why déjà vu happens? Only time will tell, and you’ve definitely heard that before.