What causes delusions?
Delusions are a false fixed belief that cannot be swayed by reason. It sounds like you are talking about deja vu. My opinion is that it is caused by crossed signals or imperfect memory (and research has proven our memories are often false), there is so much info that the brain has to process. Plus there are a lot of situations with similarities that one will experience, and if the brain remembers that similarity it may play down differences and make the similarity the focus. Old stuff is more easily identified than new.
