Effects of Truman Show life

Your question relates to "cognitive dissonance". This is when two beliefs conflict, e.g. you believe Santa Claus exists, but then discover it is dad in a red suit. Or you believe aliens do not exist and suddenly you are confronted by a spaceship landing in front of your house.

Cognitive dissonance is all about how we resolve the mental conflict. How do we deal with the new information? The Truman Show is a similar problem. You believe the world is X and suddenly discover Y.

People typically resolve the conflict by explaining away or denial of the evidence. Yes, it is dad in a red suit putting presents under the tree, but that is just a coincidence. Santa was sick with a cold, so just this one time dad helped out Santa.

When it can't be explained away, we update our beliefs. We adopt new beliefs, i.e. "Aliens do exist!"

In the actual experiments on cognitive dissonance, a group of researchers joined a cult that believed the world was going to end. That was what members of the cult believed. When the world did not end, how did the members of the cult handle the mental pain of holding an incorrect belief? Some of the cult members had sold everything they owned.

Anyway, I am oversimplifying the concept of cognitive dissonance, but it is one line of research you might find interesting...

https://core.ac.uk/download/pdf/191963998.pdf