You know, I have to give Sandy some credit here. This is a pretty good solution to a very annoying problem in Call of Cthulhu and other traditionally architected games. It is the mechanical equivalent of fail-forward mechanics for rolls.
Now, that might confuse you a little bit when phrased like that. Surely this is a mechanical equivalent of fail-forward mechanics for rolls, except that it's not, because no single roll was involved in it. In fact, the absence of rolls was involved with it. It introduces a roll where none previously existed, but it is narratively and structurally supporting the same beam.
When players are just not catching what's right there in front of them, you give them a mechanical indicator that they have failed, which immediately gives a mechanism to move forward, whether it be in the current scene or the scenario. Fail-forward mechanics take a mechanical roll and, no matter what the outcome is, something changes in the world in a way that allows things to proceed forward, but with complications.
Sandy's solution here: take a social environment, and no matter what the outcome is, something changes in the world in a way that allows things to proceed forward. The only thing it lacks is complications, and I think those would be relatively easy to bolt on.
"Sure, here's the obvious thing you've been missing, but since you've been missing it, this other thing that makes all of this far more complicated happens. Let's go!"
Here is one of my greatest creations for roleplaying games. I came up with it in the 1980s. As far as I know it has never been published officially anywhere. But it ought to be. It is, of course, the Spot Obvious roll.
In any roleplaying game, there comes a time when you, the gamemaster are rolling your eyes because your players are being idiots. Why can't they see it? Here are four examples:
EXAMPLE ONE: the giant fire elemental stands directly under a loose, cracked water tower held up by rotting wooden pillars. Your players only see a DPS race. They cast spells or hit the elemental with swords, ignoring the environment.
EXAMPLE TWO: the crumbling cavern has a clear stream of water flowing out through a wide crack in the back wall. Your players see only the dead end. They stand their ground and fight waves of infinite monsters.
EXAMPLE THREE: while tossing the bad guy's apartment, they find a calendar with May 3 marked off with the word "Roodmas" in red letters. Now the players wonder when the Big Cult Festival will be? Maybe May 1st? could it be May 10th, Mother's Day, because the cult worships the foul Mother of a Thousand Young? Argh.
EXAMPLE FOUR: there is a stone door with a giant keyhole. On the table is a giant key. The players decide it's a magical puzzle and spend 45 minutes casting Detect Magic, checking for traps, trying to pick the lock with a dagger, and ignoring the literal key. This actually happened to me.
We've all been there. Spot Obvious is my solution to keep play moving. When I am amazed the players are being idiots, I call for a Spot Obvious. The players roll against their INT x5. But here's the trick - THE CHARACTER SUCCEEDS IF HE FAILS THE INT ROLL. In other words, the stupidest characters have the best chance for a Spot Obvious!
My logic here is threefold. First, it matches real life. Often it's the smart guy who overthinks things. Second, it's hilarious. Third, suddenly the character with an INT of 8 becomes useful in the logic puzzle.
Now you may say, "Well Sandy, the GM is partly to blame in these cases because they're used to you typically overthinking puzzles." That's a fair accusation. But even if I screwed up, we still have to get past the obstacle!
You don't have to unlock everything with a Spot Obvious. For instance, say the party just defeated a goblin ambush and they're wondering where the goblins are coming from. I can call for a Spot Obvious and when/if they succeed, I say, "Remember, you actually have a wounded goblin prisoner from the fight." Then they go, "Oh yeah. Let's question him." Then there's roleplaying involved - it's not just handed to them on a silver platter.
Best of all if they all fail the Spot Obvious (it has happened), then I just sit smugly. The players know they are missing something plain and unmistakable and it drives them nuts for a while. Often they can figure it out just from that. Even if they don't, their angst is highly entertaining so we're all having fun.
Go forth and prosper.