People are fascinated by the topic of déjà vu, or the feeling that one is reliving some prior experience. The déjà vu phenomenon has been investigated by psychologists throughout the history of the discipline, and a number of theories — neurological, supernatural, pathological, and otherwise — have been proposed to explain its presumed occurrence.
A team of Dutch researchers, led by Herman Sno, have investigated the topic at length in recent years. Sno and his colleagues argue that the déjà vu experience can be examined using the hologram as a model. In holographic photography, each piece of an image contains the full information necessary to reproduce the image, a property that gives holographic images their three-dimensional qualities. The smaller the fragment, however, the fuzzier the image reproduced. Sno argues that memory may operate in a similar fashion. When a fragment of a current perception is identical to a segment of a previously stored memory, the déjà vu experience will take place. Traced to their original forms the two memories may be quite different, although based on mismatch of fragments from each they seem so similar as to be a relived experience. This idea is in contrast to other explanations, such as that déjà vu results from a micromomentary hesitation in transmitting information across the cerebral hemispheres, or Freud’s notions that déjà vu is a manifestation of the unconscious or a type of defense mechanism.