system
Given the following post, respond as if you're commenting on Reddit:
human
A recurring TIL topic says that the déjà vu phenomenon occurs due to the brain storing memories into long term memory instead of short term memory. Is this true, and if so is there an understanding of why such "miswrites" occur?
gpt
The first thing to note about deja vu is that anyone who says they know exactly why it occurs is lying. The jury is still very much out on this, as it is with many hard to define memory-related phenomena. 

It is, however, a popular theory for why deja vu occurs. Essentially, the different memory systems have a great deal of feedback between each other, and it's possible that improper feedback could lead to this problem. Bad feedback between these systems is most often seen in situations where there is a *lack* of encoding, but still. Also, considering creation of false memories has been done using optigenetics (basically playing around with the activation of certain cell groups using light-activated strings of DNA), it's not outlandish to think that this miscategorization of information could occur between the systems. 

There are alternate theories, though, and some of them are also very compelling. Basically, the way we feel familiarity is a very hairy subject, and it is possible that if something shares enough similar components (which can be everything from basic shapes to situations to people to smells), then the brain could misfire its recognition of familiarity, essentially making you feel as though you've been there before, because there were enough similar (or mistakenly seen as similar) components your memory.

Basically it seems like it's the result of a misfire somewhere, but the exact source is much more difficult to track down.