Furthermore, there are various types of déjà vu, which further complicates the task of studying it. Déjà senti, for example, means “already thought.” Meanwhile, déjà visité refers to the feeling of having previously visited a place.
However, there have been a number of theories over the years that try to explain the phenomenon. French parapsychologist Emile Boirac was the first to coin the term “déjà vu” in his book The Psychology of the Future, published in 1918. He didn’t delve into why it occurs, though.
The father of psychoanalysis, Sigmund Freud, had a theory, of course. He suspected déjà vu offered glimpses of painful memories that people had locked away. This theory, dubbed paramnesia, then became the dominant explanation for déjà vu until recently.