[RPG] What should players roll to “deduce” a solution


Say my players are in a dungeon of many keys and many doors, where if a wrong key is used in the wrong door, they will be electrocuted, ambushed, etc. This makes the players wary to just try every key in every door. The players have found a key that I describe as "a simple key, made of copper stained green with age." Our session ends, and next week the players find a locked door. A perception check has them see the lock as "relatively simple, made of aged copper, turning green." Due to my players lack of note taking and poor memory over a week, they do not associate the key with the lock. In this scenario the players may have forgotten, but the characters likely wouldn't have, but I do not want to just hand the players the answer.

After a few minutes of them unsuccessfully trying to get through the door that was never intended to be difficult puzzle, I want them to roll to recognize the similarities between the lock and the key they previously found.
An investigation check doesn't seem appropriate, as they are not investigating anything for this, just thinking about it.
A perception check doesn't seem fitting either, as they have already seen the lock and key, they just need to recognize the similarities between them.

How should I have my players roll to deduce an answer to a simple question?

Best Answer

You should tell players what their characters would know.

For the players it has been a week between finding the key and finding the lock. Both key and lock are fictional elements of a game they play for fun. Their only experience of them is as verbal or textual descriptions you supplied to them. Why would they remember?

For the characters it has been a matter of minutes between finding the key and lock. Both key and lock are real physical objects involved in their real life-or-death struggle for treasure, glory, and perhaps the fate of everything they care about. They have held the key in their hands, felt its weight, observed the pattern of its teeth and wiped its tarnish off their fingers. How could they forget?

Part of the fun of roleplaying games is to associate with your character: to imagine what they see, live inside their mindset, and make their problems your problems. Finding the key, finding the lock, and figuring out the link between the two is the problem before the characters. Retaining information about the game world is a player-only problem. You, as the GM, are the sole bridge between the players and the world their characters inhabit. It's up to you whether you want to create additional problems for the players purely because of the distance between their own experience in real life and what the characters experience in the game fiction. Some do, and consider methodically retaining information on behalf of your character part of the skill of roleplaying. I wouldn't.