[Renall]

Originally Posted by Jan-Poo

Eh, sorry if I sound a bit rude by a call that bullshit. Just because dejà-vu are something everyone has experienced it doesn't mean that you can fabricate them into another person.

And besides Battler isn't having a dejà-vu, he remembers that he or rather "his past self" defintely has been in a similar place before. That's not how dejà-vu work.

There's literally no difference between thinking you remember you've been somewhere before and actually remembering you've been somewhere before. Your brain can't tell the difference. The degree of certainty may be different between a particular memory and a passing case of deja vu, but just as there are cases of unusually strong deja vu (meaning your "memory" is more vivid than it actually should be), there are cases of weak recollection of genuine memory (which would make true experience with a place actually feel more like a vague sense of familiarity).

The brain has problems like this all the time. The brain of someone with Magic Fictional Amnesia is probably all kinds of messed up in terms of perception, memory, and vague sensation. If you are that person, it would be impossible to be sure that you're actually remembering a thing you've seen since you aren't sure if the act of seeing it was even a thing that really happened. Especially if the last time you could have physically seen that thing (if you ever did) was decades and decades in the past, such that it would be subject to the general ravages of time on memories.

I mean look at it the other way: Assume Battler didn't lose his memory, but also didn't go to the mansion for 50 years and one day walks into a room that appears to look just like the entrance hall. Do you think he's likely to think it's an exact replica of it? Possibly, possibly not. Let's say he remembers the house decently well and declares that this room is an exact copy. Do you think he'd notice if, say, a door were slightly off, or even if one were entirely absent that should have been there in an exact copy?

Psychology says he is almost certain to not notice certain details being wrong, because his vague memories will be reinforced with self-assurance that he's looking at the right thing and his memories will actually update themselves accordingly. In fact, if you don't tell him that you took a door out of the hallway on purpose, he'll likely start "remembering" in the future that there wasn't a door there. And this is a person who doesn't have any trauma-induced memory loss.

The situation you describe, like being exposed to photographs or to stories do not really work, unless he forgets that he has been exposed to them, therefore only leaving the option "I must have experienced this firsthand".

Because if he remembers that he's been exposed to them (and he should unless you pull a hypnosis) then from his perspective there is no reason to think those are his real memories rather than something he's been told.

Actually, a great many of your own childhood memories are probably wrong, fake, or distorted by time. It's just something that happens. It's also pretty well-documented that you can convince a person that an event has happened to them in the past that didn't with just a little bit of experimental setup and priming questions.

Vivid memories are harder, but it's certainly possible over a long period of time. Some people have conjured vivid memories of things like alien abductions, and while those memories - which are factually false - were not initially particularly strong, long-term belief that those memories were true leads people to eventually produce extremely strong and consistent stories about the "events" which at least sound plausible to a person open to the possibility that such events could happen. Even when they provably didn't, such as physical evidence that a person was not at the location they said they were when they were "abducted." If you can't prove the events didn't happen (their whereabouts that night can't be proven), it gets even harder to convince someone that what their memory tells them so clearly occurred actually didn't. Even though we know that it in fact didn't.

And again, there is no discernible difference whatsoever between forgetting you saw a picture of something and remembering that you saw the picture later and accidentally leading yourself to believe you saw a picture in the past and just forgot about it because circumstances led you to believe that's where your familiarity derives. Psychologically, you cannot tell that was the case off your memory alone. And the most vivid memories are often the ones you can't trust, except when you can.