We have a lot of questions on how to prevent metagaming on this tag. But usually the metagaming is something like
Using player's knowledge to optimize your character's actions.
Now, I've experiencing something that is kinda the opposite of the usual – instead of metagaming to make an optimal choice, the player is trying to avoid metagaming and ends up making a choice way too suboptimal – something that even a player without knowledge about that wouldn't probably make.
Some examples of situations I'm talking about:
- An NPC lies to the character, which rolls an incredible 1 on Insight. He then role-plays believing this NPC. Then a strong evidence that the NPC was lying shows up, and the player role-plays still believing the NPC, because he thinks that the evidence is only strong because he knows he rolled a 1 (when the evidence is actually strong enough).
- A player has already played an adventure or module before. He knows this hallway has a trap. He doesn't even check for traps, because he thinks he only wants to check due to his knowledge that there is a trap, even though the hallway is suspicious and the character would probably at least check it.
- The player knows a monster has a specific elemental weakness. He then proceeds to not ever use a spell with that type of damage because he thinks he only would use it because he knows the weakness.
- The player knows a monster has a specific elemental immunity or resistance. He then proceeds to use a Fireball in the Fire Elemental. You got the idea.
So, basically, the question is:
How do I prevent my players from not using their character's knowledge because they think it is only their player's knowledge?
Note: Generally, I feel that the player's knowledge will always inflict some bias on their decisions, but I want ways to reduce this impact.
This might open a more general question: What does my character know? This is a footnote because it is not the main question here, but I feel that answering this easily answers the main question.
As implied, metagaming in order to optimize and have advantages on the campaign are seen as a bad thing on our table
Best Answer
Make their knowledge uncertain
Tell them: "This my game and my world. I might change some things that you might have read in the books or the module."
Now the player cannot ever be sure that their background knowledge is accurate. It might be and there is a high chance it is, but not 100%. Almost like they just heard a few (possibly tall) tales or myths about the monsters and dungeons. Which is a completely reasonable assumption about a character. Their player knowledge just became character knowledge.
Also note that I did not say to change anything, just to say so. Actually changing anything is not required for this to work, but you might want to at least throw some minor changes in just so they or you can point at them and say "Aha! A difference!".
About the insight roll example
This is not really a metagaming issue, but a problem with communication. You and the player do not have the same understanding of what a nat1 means and/or how certain the evidence gained later is. Do not be afraid to clearly state what you mean. Descriptive and immersive narration has its limits and sometimes you have take a step back to avoid misunderstandings. However, even if you do that, there might be issues. You cannot completely stop a player from just running with a misunderstood idea. Agency over their character gives them the power and right to do that. If they choose not to listen to your descriptions, you can only try to compensate. I would recommend making the same evidence available to other PC-s so they can confront the character in the game.
If the issue persists or reappears, then it is not an in-game problem, but an out-of-game one. As such it should be solved as one, by talking to the player about it.