Neuropsychiatrist and anomalistic psychologist Dr. Vernon Neppe shared his intensive research into the phenomenon of deja vu. The experience is defined as feeling as though something has happened before-- that you've already been in a place, or heard or seen something, even though it should be unfamiliar (see list of various subtypes).
Early interpretations of the experience associated it with temporal lobe dysfunction, and while that holds true in some cases, Neppe found that deja vu could also be related to nostalgia, relief of anxiety, and paranormal experiences.
He is particularly fascinated by the paranormal or psychic connections with deja vu. The sense of "time distortion" that can accompany the experience relates to notions of reincarnation and having lived before, he noted, and premonitions and precognition share a similarity to the phenomenon as well.