Ask Angry: Passive Skills, Active Skills, Perception, and Knowledge

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What is this? Is this ANOTHER installment of Ask Angry? Yes. Yes it is. So many people have been sending their questions to with the subject: ‘Ask Angry’  that I can’t possibly just do this once a week. So many desperate souls would be going unhelped. So, from now on, you’ll get a new Ask Angry every Tuesday AND every Thursday. Because I’m a motherf$&%ing saint! You’re welcome!

A Kind of New GM going by the name: “KindOfNewGM” Asks:

Hey Angry, I’m Kind of New Gm. I’m a kind of new gm and I’ve always noticed how divisive it is – among other things – to ask GMs “How do you use perception and insight?” Please explain perception, insight, and the passive uses of anything to us all. Examples and the reasoning behind it all would be great. Also if you can, include an explanation of “knowledge skills” as well sometime.
Help me AngryGM, your my only hope!

Holy f$&%nuggets, Kind of New GM, did someone put you up to this? After Charisma and Intelligence, passive skills are my next biggest f$&%ing gripe. I hate passive skills but I LOVE talking about why. I’m going to try and give you a neutral, unbiased answer, but I don’t know if I can. Because this topic really gets my goat. And pisses it off.

So, first, let’s talk about the idea of active skills vs. passive skills. An active skill is a skill that is triggered by a character actually making a choice and doing a thing. For example, searching a room for traps or secret doors or trying to locate the hidden goblin that was right there a minute ago? Those are active uses of Perception. And those are easy to deal with. Because the character actually does a thing and you can see the thing they are doing and roll the check. Simple.

Things fall apart when skills are passive. A passive skill is a skill that is just sort of supposed to happen. When you walk into a room, you MIGHT notice a thing is there and you might MIGHT not. Noticing or not noticing is automatic. Your eyes and ears and senses and brain just work. You don’t have to flex your eyeballs to get them to see things. That’s passive.

So, Perception is a skill that can be active and can be passive. Got it? Now, I’m still talking conceptual. I’m not talking about the actual game mechanics. I’m just defining some terms.

Now, Insight is the ability of a character to read body language and subtle cues and figure out things aren’t right. To detect when someone is not telling the whole truth. To detect when someone isn’t themselves. Moments of hesitation, furtive glances, odd tics and tells. Right? That’s insight? But so is spotting inconsistencies in the things people say. You can actually think of Insight a bit like the social equivalent of Perception.

And it’s easy to see how Insight can be passive, right? When someone lies to you, you might notice the inconsistencies and oddities. When someone is pretending to be someone they are not, you might realize they are bluffing. When someone is under mind control, you might notice their words aren’t really their own or the swirly hypnotism lines in their eyes.

But Insight can also be active. Just like you can search a room by tapping on walls, running your fingers along door jumps, feeling for drafts, peering under and behind things, and so on, you can also search a conversation if you feel things are untoward. You can ask probing questions or try to catch people in contradictions. You can give misleading information and see if people fall for it, indicating they are trying to bluff you. You can try to tease out their motives by making accusations and watching their response. These sorts of active probing SHOULD fall under Insight. But they rarely do.

Perception and Insight should be rolled (used actively) only when the players purposely do things that count as searching or probing. That is, when the players interact with something in the world with the express purpose of discovering things that are hidden or not what they appear to be, that’s when they roll Perception and Insight.

Passive Perception and Passive Insight are target numbers. They are the numbers SOMETHING ELSE rolls against when they are purposely trying to be deceptive or sneaky. A goblin is hiding, he rolls Stealth against Passive Perception. A con artist is bluffing, he rolls Bluff against Passive Insight. That’s how it SHOULD WORK.

Now, this is where I have an aneurism and here is why it gets so f$&%ing confusing when it really shouldn’t be. Sometimes, the thing that is actually trying to be sneaky isn’t the one rolling the dice and whole f$&%ing system falls apart.

For example, traps. Traps are hidden things. They are TRYING TO HIDE from the PCs so they can jump out and kill them. I know it sounds weird to talk like that, but mechanically, that’s how it should work. A trap is trying to hide in a room and a PC MIGHT notice it just by walking nearby. Depending on the edition of D&D, the PC might roll Perception or the Passive Perception might be compared to the DC of the trap. Neither of those mechanical answers actually line up with how things SHOULD work. So it’s confusing as f$&%. You can think of the DC to notice a trap or secret door as a “pre-rolled” Stealth check. The door or trap rolled a Stealth check AGAINST the PCs Passive Perception.

If you keep all of that in mind, you should be able to make it work out.

Now, Knowledge checks.

Knowledge checks have the same goddamned problem only worse. Let’s talk about them in the same terms.

First of all, Knowledge checks are passive. You generally take an action to know something. You see a thing and you either remember something about it or you don’t. You don’t have to screw up your brain really hard and squint your eyes or anything. You just remember things or you don’t. Or you remember things a day later after it doesn’t matter anymore because brains suck sometimes. But in general, Knowledge is a passive check.

And that’s already a problem because there is no ACTIVE THING. You can argue a trap is TRYING to hide from someone and you can point at the thing doing the activity and therefore say Passive Perception is the target, the chance of success. But Knowledge doesn’t have anything like that. Knowledge is just a coin toss. Either you remember something or you don’t. It’s just a f$&%ing die roll to see if you get a clue or not.

In that respect, though, players should NEVER NEVER EVER ask for Knowledge checks. And they shouldn’t have to. The minute they see a thing they might know, the GM should call for a Knowledge check and give the appropriate information, just like when the goblin is sneaking and the con artist is lying. Most GMs don’t follow this rule though. They wait for the player to “trigger” the knowledge check by performing some stupid non-action like “I examine the thing, do I recognize it” or just flat out asking “I have Religion, do I know what that icon is?” This should never EVER happen if you’re a good GM.

But, now the question is, if Knowledge can be passive, can it be active? I would argue that yes, yes it can. Every field of study includes not only the collective body of information that it consists of, but also of the ability to use the right tools to get the answer. Arcana is not just “knows a lot about magic.” Arcana is “knows the field of academic of study of magic.” Someone versed in Arcana should know how to research magical answers. How to use libraries, how to find experts and ask the right questions, and how to conduct magical experiments. Someone schooled in Religion doesn’t just know about the gods, they also know rituals and prayers and proper ways to deal with priests and ways to make offerings and gain specific deity’s favor. They also know the scriptures well enough to know where to look for an answer if they don’t have it. If someone doesn’t know the prayer to stop undead from rising, they at least know which experts to consult or what books to start with.

In that respect, Knowledge can be active. And it really should be. But GMs rarely use it as such. Knowledge skills are only ever about recall. And then they are misused because the GM insists on direct questions and non-actions, as if Knowledge is a button the player has to press.

Anyway, I hope all of that helps.

15 thoughts on “Ask Angry: Passive Skills, Active Skills, Perception, and Knowledge

  1. THIS! This was really helpful. Not just in breaking down the mechanics re: passive checks, but in giving me a better way to think about them in the first place. Passive checks drive me a little nuts when I run my games. I used to think it was because I was kind of new and just didn’t understand the mechanics properly. But now I realize that the mechanics are kind of messed up to begin with, and run counter to how things work in real life. And I’m not the kind of simulationist who demands my game mechanics mimic reality, but sometimes something’s so ingrained within us that the rules fight against our own instinctive approach to something like knowledge, etc. And THAT’S what was throwing me for a loop. I’m not sure if I’m going to homebrew the rules a little bit to make them more intuitive, but even if I don’t, I at least feel more comfortable working with what the rules are telling me. THANKS!

  2. Though I think it is implied, I think knowledge isn’t only remembering or at least be able to now the right questions. I think it would also be the ability to synthesise and extrapolate your knowledge. The wizard who grew up among the elves may have never explicitly learned about dwarven protective wards or golems or whatever; but being versed in aranca, he should be able to put 1+1 together and from all he know about magic in general, should let him find make an educated guess about the what he is dealing with and how it works (maybe even how to disable it).

    Also a ranger that have never before seen that kind of nest, should be able to at least get some clues about what lives in it (there are small bones around and feathers – it’s probably a bird of prey etc.)

    Actually could that be like if you fail a “passive” knowledge check you could make an “active” one to try to figure out what’s going on. Not sure why players wouldn’t always just do that, but maybe there are cost – most obviously time. Maybe there would be a higher probability of discerning something false?

  3. So what about if they take an action and do worse than their passive score. For instance, a player feels an ambush is likely (say there is a barricade on the road) and says “I’m trying to see if there are any hidden bad guys around”. They then roll a 2 and combined with their wisdom mod of +4 get a 6 on perception. Normally if they’d just stuck with doing nothing they’d have a 14.

    I guess the answer may be that if the hidden bad guys were detectable on a 14 they would already have been spotted. Does this mean they can roll and try and do better than their passive but never do worse?

    Also, is a secret door trying to hide? Just like a trap? If they don’t bother to search for a secret door and it’s not hidden that well, will they just find it anyway with their passive?

    It seems to me that the whole passive thing was a solution to a problem (DM rolls to see if they see something and the party says “Aha! He’s rolling, there must be something to see) that created more problems than it solved.

    • Yes, in the first case PC’s can roll to try and do better than their passive, but never worse. The player trying to spot an ambush automatically notices everything that his passive score of 14 would reveal, but trying to spot something else (his active score of 6) didn’t reveal anything new.
      In your second example, the DC of the hidden secret door is the target for PC’s passive AND active checks. So if the secret door is poorly hidden (say, DC 10) most PC’s will notice it automatically just by wandering around and glancing at the location. If it’s hidden a little better (DC 15) then only the more perceptive PC’s will notice it automatically (passive), but if nobody’s passive perception is 15 or higher then they get a chance to roll for it if someone says “I want to check this wall to see if I notice any secret doors” (active perception).

      • Okay, there is a lot wrapped up in these questions… and they really do illustrate the problems I alluded to.

        First of all, there is nothing wrong logically with an active roll to search for the goblin being “worse” than the Passive Perception. That’s for two reasons. First, because Passive Perception is not a skill roll, it’s a target number for someone else’s skill roll. You can think of it in terms that the goblin “failed to hide,” not that the PC “succeeded to notice.” Always look at the action from the perspective of the creature taking the action. In the case where the goblin rolls Stealth against Passive Perception, the goblin FAILED to hide. Or SUCCEEDED at hiding. He’s the thing that succeeded or f$&%ed up.

        Now, the goblin is hidden somewhere in the room and someone wants to go searching for them. They are actively searching. So they take the action, Now, it’s beholden on them. They either FAIL to search or SUCCEED on the search. They do a good job. Or a bad job. And it’s on them.

        It seems weird, because you want to think “well, it’s about senses either way,” but it isn’t. It’s two separate, distinct actions with two different sources of success or failure and two different sets of choices and skills driving that success. And things change moment by moment. So you can notice something one moment and then fail to notice it the next.

        The other thing to consider is that if the goblin fails to defeat the Passive Perception, the goblin ISN’T hidden. The result of the Active Roll is immaterial because the game never reaches that point. From a practical standpoint, if your Passive Perception is good enough to change the outcome, you don’t get to the point where you need an active roll.

        As for the “is a secret door trying to hide” or “is a trap trying to hide?” When all else fails, you can think of it like the creator of the object TRYING to conceal it. At some point in the distance past, the creator rolled a skill check to “conceal the trap” or “conceal the secret door.” That check has gone unresolved until some idiot PC comes along who might notice (or search for) the damned thing.

        As for the Passive Perception being the solution to a problem no one had, it actually just exposes the bigger problem that D&D is built around an ACTION resolution system but never bothered to figure out the difference between an ACTION and things that just happen. It’s the same weirdness you get between the Attack Roll and the Saving Throw.

        Sometimes, when someone attacks someone else, the ATTACKER rolls an roll to see if he kills the victim. Other times, when someone attacks someone else, the VICTIM rolls to not die from the attacker. You can try to draw a conceptual line and point out that it’s all about whose skill is the bigger determining factor in the outcome, but when you start having some spells that arbitrarily involve attack rolls and other similar spells that involve saving throws, that argument falls apart. There is no conceptual understanding and it can make it hard to adjudicate.

        • Okay, so the secret door rolls to hide at the time of its creation, and that is forevermore its active roll against the PC’s passive perception. But I see a problems with this, which relates to how the secret door’s active hide DC is set in the first place. If it was a PC doing the rolling, the PC would roll and apply whatever bonuses he has. But things like secret doors are generally not provided with a bonus, they usually have a DC that is fixed by the type/level of object. So if a PC has a high enough perception, there is never a random element, because he can always count on an object of a given level/type failing its hide check. I don’t know about you, but I dislike that.

          So I think it follows from your argument that objects of a certain level/type should not have a fixed DC, but rather a fixed bonus (which is easier than inventing a creator and calculating his bonus every time). For every such object, you roll to determine the active hide score (which presumably doubles as the passive score when the PC is actively looking). This creates more variation (or it would, except I think many GMs would reject passive scores that end up being “too easy”).

          But then, if your system has “take 10” rules, the creator can be assumed to take 10 a lot of the time. And you end up with standard DCs again, with the high Wisdom character expecting to detect everything automatically. So either you lose the take 10 rule, or you come up with something else. (The something else I was using prior to reading your article, is that the passive score does not lead to automatic detection, but triggers an active check by the PC when he might otherwise not have been looking for anything. I am still mulling over whether your article changes this for me.)

          So I guess the short question is: should you allow the creators of secret doors to take 10 on their hide check?

          • Okay, skippy… first of all, I’m not arguing you should or shouldn’t do anything. In fact, I don’t have an argument. I’m trying to illustrate different ways of thinking about active and passive skills with analogies. And you’re taking this analogy as a game mechanic. Here’s the thing: the reason so many people have problems grasping active and passive skills is because the system isn’t actually very consistent about them. Sometimes, the actor rolls to do a thing. Sometimes, the target rolls to counter a thing. And sometimes, as in the case of Passive Perception vs. the Notice DC of a secret door, no one is rolling anything. Conceptually, it’s a huge mess.

            I mean, if you want to rewrite the f$&%ing system to make it make some kind of sense, then, yes, absolutely, secret doors and traps should have stealth “skills” that they roll against Passive Perception. Or something like that. But D&D wasn’t designed around that.

            Honestly, the whole “passive thing triggers an active roll” is even more of a mess. Why have two stages of it? If you want to have active rolls trigger on their own without an action, just do that. Dump passive perception altogether and have players roll whenever there is something hidden they MIGHT notice. But that’s up to you.

  4. I was hoping your answer would help with a problem I’ve had, but it hasn’t and maybe I’m not seeing it yet. I have to wonder if it requires another article. Maybe traps alone require another article.

    I’ve looked around and some online gm advice I’ve seen is that…the players dealing with the trap is the fun part. To avoid “gotchas”. To provide clues. To try to avoid a trap that could be replaced with lightning from the sky that damages players. Thus you should always tell them there’s a trap. And treat traps like puzzles. The perception skill and others like it should be eliminated from the game. Or the players should be given an elvish blade that glows blue when traps are near so they know when to use spot.

    Anyway, with this answer another question I would have is…
    How do I make a “trap area” encounter? A room that is empty except for a trap or traps. I don’t know if four is better than one in this case. I’ve seen it in published adventures and I just don’t know what they are getting at.
    A room of traps in a dungeon, an obstacle course of traps, an entrance to a dungeon that is only trapped…
    How do I make it happen in the game?

    • Excuse me for just one moment. I need to go smash a hole in the wall with my forehead…

      Okay. Back.

      If THAT was your question, why didn’t you ask THAT question. If you had asked THAT question, I would have answered THAT question. But you didn’t. You asked a completely different question. If you wanted THAT question answered…

      Excuse me a second…

      Okay. Back.

      All right. Fine. First of all, dealing with a trap is NOT fun. Overcoming an obstacle – any obstacle – is fun. If you figure out how to do it. If you’re smart enough to guess that it’s there and understand how it works and then circumvent it, that’s fun.

      A trap is, by definition, lightning from the sky that damages people. A trap IS a gotcha. Your problem isn’t perception, it’s that you don’t like traps. I would advise you not to use traps. Stay away from them. Because part of what a trap does is catch people by surprise. And honestly, there’s nothing wrong that. Booby traps kind of suck. Because if you use them too often, the players just search for them EVERYWHERE. If you only use them once in a while, the chance that the players will find them is pretty slim. And then they are just gotchas.

      Removing Perception from the game doesn’t solve the problem. And you will find that just telling players “your trap sense is tingling” isn’t satisfying. It just takes away part of what feels good about dealing with traps (the sense of outsmarting the creator and seeing the trap coming).

      But, hey, if you’d like to know more about dealing with traps, did you know I write a twice-weekly column where I answer the questions that people ask me? Just send an e-mail to and put Ask Angry in the subject.

  5. Hi Angry, great article and this is something that still gives me headaches when I DM. More specifically, I have a hard time deciding what happens when characters fail a knowledge or perception check. For example, a character searches for secret doors, rolls perception and misses the DC. What do I say? How do I narrate failure in a way that doesn’t tip everyone else at the table off to the possibility that there is a secret door and want their characters to search too? Going back to your excellent adjudicating actions article, if there’s no consequence to failure, just let the PCs succeed, right? This grates a little bit for me. Probably because my brain is struggling against 30 years of playing the game the other way that says “but you can’t just let people auto succeed, they have to roll a dice first!!”

  6. Pingback: Ask Angry: Traps Suck | The Angry GM

  7. Given your comments here on Knowledge checks, what do you think of the “fact points” house rule? Here’s how it goes:

    When you roll a Knowledge check, there’s a low DC. Very low. If you make this DC, the DM tells you the basic stuff that everyone knows, common folklore, first result on Google, kind of thing. If it’s a big secret and common folk don’t know about it, you’re told that explicitly.

    Then, for every few points past that DC, you get a Fact. How many depends on a simple easy/medium/hard judgement based on the scarcity of the information you’re after and the likelihood of it being in the place you’re looking. Looking in a wizard’s laboratory for information on a spell? Easy; one fact per point. Looking in a noble’s private collection for information on a rare monster? Medium; two points gets you a fact. Looking in the public library for information on a secret cult? Hard; three points gets you one fact.

    So, you’re after information on gricks, DC is 12, it’s medium, and you rolled 18. Six points over; three facts. As a DM, you might say “trawling through the books and scrolls, you find three passages that seem promising, and copy them onto a spare parchment”. As a player, you put “3 facts about gricks” on your character sheet. Then, immediately or at any point you fancy, you can ask the DM one specific, bounded question about gricks, and get an answer in exchange for a Fact.

    “How do they hunt?”
    “You check your notes. It seems they hide in amongst rock and debris alongside routes that prey use regularly, and then pounce when they sense movement. They drag captured prey away from the route so as not to give away their ambush site. You’ve got two Facts left.”

    I came across this a little while ago, and I’ve been thinking of using it. It makes the basic information a lot more like a passive DC, and it makes the *active* rolling of the Knowledge skill an actual *activity* of researching. Without a book or archive or something, all you have is that base DC, and you could just have them take a 10 and treat it as a passive check.

  8. I know it’s an old article, but I found a perfect example of how messed up the Active/Passive system is, and how poorly conceived and/or explained it is.

    In the Starter Set (Lost Mines of Phandelver), there’s a point where the characters encounter a simple trap.
    The book explicitly says that if the characters are Actively searching for traps then they use their Passive Perception score, but if they are Not Actively searching for traps then they have to roll an Active Perception check.

    …Because reasons??

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