Biology 202
2002 First Paper
On Serendip

Where or When (Words by Lorenz Hart, Music by Richard Rogers)
When you are awake; The things you think come from the dreams you dream; Thought has wings-; And lots of things- are seldom what they seem; Sometimes you think you have lived before; All that you live today.; Things you do – come back to you,; As though they knew the way.; Oh, the tricks your mind can play!; It seems we stood and talked like this before.; We looked at each other in the same way then; But I can’t remember where or when.; The clothes you’re wearing are the clothes you wore.; The smile you are smiling you were smiling then,,; But I can’t remember where or when.; Some things happen for the first time,; Seem to be happening again - ; And so it seems that we have met before, and laughed before and loved before,; But who knows where or when! (1)

It happens to many people – you are there and it’s as if you have already been there, you know what is going to happen next and it seems a part of another life you have lived. Some claim that déjà vu is signifying problems in your mental state, that you are probably losing your mind and start living in the hallucinating world of a person with mental problems. Others accept it as a fact of life. But in a survey, over 80% of the participants who reported having experienced déjà vu, denied a possibly clinical condition before their déjà vu incidents, such as mental and physical fatigue, depression, stress, anger, fear. And surveys among random groups of population show that nearly all people experience déjà vu. The statistics varies from 30% to 96%. (3)

The concept of déjà vu is not very well studied. Even though a common phenomenon, most of the studies have concentrated on clinical populations such as psychopathological patients. (6) Neppe’s definition describes déjà vu as any subjectively inappropriate impression of familiarity of the present experience with an undefined past. (2)The term "already seen" was first used in 1876 by E.Letter Boirac who called it "la sensation du déjà vu." In 1896 F.L. Arnaud introduced it to science. (7)Many researchers are cautious when dealing with instances of déjà vu because of the chance the person who experienced the sensation may have read or seen something that is in his unconsciousness triggering the impression. There exist seven major phenomenological classifications of the déjà vu experience: a disorder of memory, a disorder of ego state, an ego defense, a temporal perceptual disturbance, a recognition disorder, a manifestation of epileptic firing, or a subjective paranormal experience. (2)While reading the different models of explanation that are used (psychodynamic model, physiological model, holographic model, dream and reincarnation, distortion of the sense of time) in discussing déjà vu, I decided to focus on the physiological explanation and the temporal perceptual disturbance. (3)

Of all the five senses it seems that déjà vu occurs only to the sense of sight. A possible explanation of the phenomenon could be the fact that everything seen by a person is in reality perceived independently by the two eyes. So if the signal path to the brain has a slightly different length for the two eyes, then the brain can get signals from one of the eyes faster, process them and turn them into a memory. By the time the signal from the second eye has arrived, there would already exist a memory of the experience, and thus the feeling of a déjà vu happens. The interesting thing is whether individual memories are in some way time marked or whether the brain’s memory keeps "time stamps" on them. (8) Often times we have a time concept of an experience because the memory involves a certain moment of the day, a certain stage in our life. But if the memories are recorded with almost now time difference between each other, and in the case when you do not get déjà vu, do they just mold together and form some kind of a puzzle composed of very fast recorded memories. Experiments have shown that the human brain can only distinguish two individual visual events with respect to time if they occur more than 25 milliseconds apart. (8) So if a person has an optical signal path impairment which results in the image from one eye coming after the other with more than 25 milliseconds, then the brain can think that they are two different incidents instead of parts of one and the same. Once the optic nerves deliver signals to the thalamus, it is responsible for transferring the information to the primary visual cortex in the occipital lobe. But there can be a delay in any part of this journey which would result in two separate images arriving in the memory at different times. If the time difference is great enough a déjà vu can happen. (8) Sno describes this as the event "being experience and recalled simultaneously." (5)

There is a research done by Vilayanar Ramachandran on the rare condition of blind sight. A person is unable to see but experiences some things that can only occur due to sight. Dr.Ramachandran has discovered that humans actually have two totally separate brain processing methods regarding visual information – the standard thalamus-centered pathway and a more primitive method which is not used in most cases because of evolution and the better efficiency of the thalamus one. However, the argument goes, if the extinction of the primitive method has not completely taken place in some individuals, then maybe they would experience much more occurrences of déjà vu. (8)

In any case, the thing that is most interesting to me is what does déjà vu signify for our memories formation. The wholeness of a memory depends on how fast the perception of the different eyes reached the thalamus. And what becomes an objective reality then? Because something that has objectively happened as a single incident, depending on the functionality of our visual pathway, could become two separate incidents, a split reality. St.Augustine mentiones the phenomenon of "falsae memoriea" in relation to déjà vu, but is a split memory a false memory?

WWW Resources

1)Dreams and Deja Vu
2)The Psychology of Deja vu
3) Deja vu
4)On Deja vu
5)Been There, Done ThatTime magazine
6)The Déjà vu Phenomenon and Personality
7)The Déjà vu
8)A Theory on the Déjà vu Phenomenon

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