Dear Sasquatch: Déjà vu
Dear Sasquatch: My girlfriend and I were talking about déjà vu experiences, and she says they are proof that humans have innate ESP abilities that we just have to develop. Do you think this is possible? Is déjà vu a form of precognition? —Alison P.
My girlfriend and I were talking about déjà vu experiences, and she says they are proof that humans have innate ESP abilities that we just have to develop. Do you think this is possible? Is déjà vu a form of precognition?
Before looking at the least likely explanations for a phenomenon, it makes sense to see if simpler explanations exist. (OMG, I totally knew I was going to say that before it happened!)
Déjà vu experiences are an interesting area of cognitive, psychological, and neuroscientific study. Many findings point to the different ways we experience and process memory, and the different parts of the brain involved.
For example, two types of memory that are related to different parts of the brain are recall (prefrontal cortex and hippocampus) and familiarity (parahippocampal gyrus and its cortical connections).
With recall memory, we tend to remember fairly specific details, such as what we had for dinner last night. Memory based on familiarity is fuzzier, such as recognizing someone but not being able to place the person. Sometimes, this familiarity is based on some qualities about the person that are familiar, even though we haven’t actually ever met.
So some déjà vu experiences may be related to experiencing a situation that is similar to a past experience but without more specific details of that past memory stored in recall. So rather than recognizing that this is similar but not the same as a specific past memory, we have only that sense of familiarity to go on, so it seems as though we are somehow remembering our present, as though our brains were predicting it as it happened.
Similarly, our brains are always seeking patterns, to complete the picture. Our memories are as a rule a combination of factual recall and our own imaginative connecting of the dots, which is one of the reasons eyewitness testimony is so unreliable. The fabricated parts of our memory are just as real to us as the factual parts.
So when we encounter something familiar, we often are able to recall a memory or memories that explain that familiarity, but even when we don’t recall these specifics, we tend to fill in the gaps, essentially creating the memory out of our current context based on those nuggets of familiarity.
Another theory is related to the differences between short-term memory and long-term memory. Memory isn’t a simple matter of storage in the brain, like putting my Zubaz at the very back of the top shelf of my closet. It involves molecular and cellular changes as well as functional and systemic changes to structures.
To vastly oversimplify for our purposes, let’s look at some of the structures involved. The hippocampus works with the neocortex to form new memories. The neocortex essentially distributes the information to the relevant parts of the brain (sights to the visual cortex, sound to the auditory cortex, etc.). Eventually, through multiple processes, the memory is consolidated to the point where we can access it without the hippocampus being involved. This is long-term memory.
Some of the more interesting explanations for déjà vu are related to a glitch in this processing. For example, if a new memory bypasses short-term memory processing and is experienced as a long-term memory, or if there is a delay in our sensory perception so that we sense the present slightly after it is begun to be consolidated as a memory, we will experience and remember events at the same time.
Any or a combination of these explanations are far more plausible than the idea that we have latent ESP powers because they are rooted in evidence of how the brain works and in the study of memory and, particularly, brain damage (such as what happens in Alzheimer’s, when a person cannot create short-term memories but has no problem with long-term recall).
The precognition theory is supported only by wishful thinking—which, incidentally, can also be explained by neuroscience.
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