D&D 5E Perception, Passive Perception, and Investigation

[DEFCON 1]

But hidden objects are explicitly called out as using perception in the PHB.

I don't care what the rules say. I do it the way I do it.

We've already had several other people recite page and verse of what the "rules say", so there's no need for me to reiterate them. Instead, some of us have offered up our own interpretation of how the rules could work (and in my case, I think work better.)

If @Azzy wishes to just go with what some people have said they feel the rules are as written, Azzy certainly may. But if Azzy doesn't particularly like the idea that "by the rules" Perception is used to find every single thing in the game (thereby making that skill head and shoulders more useful and more often rolled than all the other 17)... some of us have set out alternatives for them to think about instead.

 

[clearstream]

Perception is for detecting where hidden objects and creatures are based on senses.
Investigation for deducing where hidden objects and creatures are based on clues.

You use Perception to find the hidden goblins via their noises and image.
You use investigation to find the hidden goblins via chairs they moved before hiding.

Active Perception/Investigation checks are either initiated by character looking or at a time where the action could affect the check (aka combat)
Passive Perception/Investigation floors are either initiated by character hiding or when the character becomes close enough to sene the hidden object or character.

That is close to my original stance, but I found it sometimes confused my players. It wasn't always clear when something like a secret door was something you my sense, or something you might notice by clues. And I didn't desire to just let either apply. That is why in the end I disambiguated across the creature/artifact divide. Player expectations are more reliably met.

 

[DEFCON 1]

One of the things I do not like about the game using Investigation to "deduce" how things work is that it runs completely counter to the idea of the DM putting things in place for the players to figure out.

If I put in a secret door and I think up some hidden mechanism for the way it is meant to unlock and open... why would I want to have a skill in place that players would use instead of them figuring out how the mechanism works? Why bother thinking up the way to open the door if the skill check pretty much gets around needing to think about how to open the door by the skill "deducing" the answer? And if you say "well, the Investigation skill only gives the players clues to figuring out"... I find that to be such a ridiculously narrow focus that I don't even think the skill should be bothered to be in the game then.

Here is what I would expect to happen... a PC says "I'll look for secret doors". Okay, they make a Perception check and I tell them "you think something is there". They then either go straight to "I Investigate", they make a check, and I reveal the information and clues about the situation they probably could have been given on the Perception check... or the players start asking the prototypical questions to find info like "is there a breeze", "do I hear anything", "is there a crack in the wall", "are there any protrusions to press" etc. etc. And then after I give them all this info, they then say "Okay, let me make my Investigation check to piece it all together". As though once you get given all the clues, the skill check then solves it for you. What exactly is the point of that?

So I just avoid all that and use Investigation as the "object finder" skill and have them make one roll and then if the door is secured in some additional way I'll start giving them clues on how to open it as they ask the right questions. And no skill can be used in place of actually figuring out how the door opens. I went through the effort of coming up with that "puzzle"... the least you can do is try to solve it yourself.

 

[Asisreo]

I don't care what the rules say. I do it the way I do it.

We've already had several other people recite page and verse of what the "rules say", so there's no need for me to reiterate them. Instead, some of us have offered up our own interpretation of how the rules could work (and in my case, I think work better.)

If @Azzy wishes to just go with what some people have said they feel the rules are as written, Azzy certainly may. But if Azzy doesn't particularly like the idea that "by the rules" Perception is used to find every single thing in the game (thereby making that skill head and shoulders more useful and more often rolled than all the other 17)... some of us have set out alternatives for them to think about instead.

I'm not telling anyone how they should play. If you play your game like that, by all means.

But I do want to clarify things in case some people don't quite understand since the rules themselves can be a little tricky.

And, in my opinion, its better to understand the rules before houseruling so the DM can understand exactly how their changes affect the rest of the game and if its for good or bad. When someone is on the fence like Azzy, I want them to have a clear sense of how the rules work before taking on too many suggestions that, while valid and can work for some, may not work for his group in particular.

 

[Minigiant]

That is close to my original stance, but I found it sometimes confused my players. It wasn't always clear when something like a secret door was something you my sense, or something you might notice by clues. And I didn't desire to just let either apply. That is why in the end I disambiguated across the creature/artifact divide. Player expectations are more reliably met.

I use the words "unusual" "strange" or "weird" for Investigation.

A dwarf notics a secret door in the wall because the shapes and masonry of the stones are often. Everyone can see where the door is. You have to investigate to say "Hmm, that's weird", "That's a strange pattern" or "It's unusual for that to be there."

Once I expected to my players that Investigationis to deduce that something is "off" or "too on", they got it.

Or as my cousin says, "I investigate to see if this is Ambush City." He always forgets the "Population: Us" part.

 

[Ovinomancer]

Passive check are used when an action is repeated over time, or the GM wishes to have a check without the player rolling. From the basic rules:

A passive check is a Special kind of ability check that doesn’t involve any die rolls. Such a check can represent the average result for a task done repeatedly, such as searching for Secret Doors over and over again, or can be used when the GM wants to secretly determine whether the characters succeed at something without rolling dice, such as noticing a hidden monster.

So, then, when do you use it? You use it just like a normal check, when the player declares and action for their PC that has an uncertain outcome (and a consequence for failure, if you're using the Middle Path). Specifically, when the player declares an action that their PC is repeating, like looking for traps while moving along the passageway, or looking for evidence of secret doors while doing the same. If a situation arises where the outcome of that action is uncertain, you can use the passive check because it's a repeated action over time -- essentially the average of a number of checks. The key, for me at least, is that passive checks are not universal applications to all possible actions at all times. If you move down the hallway looking for traps, then it's not going to find other things that could be perception checks that aren't traps. The action declaration matters -- passive perception isn't a radar warning system. In reality, what I do, since secret doors are similar to traps, would be to apply full passive perception to the one, and disadvantage to the other.

In combat, it's already assumed that everyone is always looking out for danger, so using passive perception to detect hidden foes makes sense -- this is a default action declaration that's free to the characters (ie, takes no action). This is, in context, where the "passive as floor to normal checks" comes from -- you can take an action to Search for a hidden foe, but since you were already using passive, if the foe's DEX(stealth) check was lower than that, you'd have already see him, so it effectively acts as a floor in this case. Similarly, if you're looking for traps while moving down a passage, but declare a specific action to search a feature the GM described for traps, then you were already looking for traps and if one was present on the feature you'd have already found it if it's DC was below or equal to your passive score. This is the context for passive as floor. Since it requires action declarations for passive anything to be used, then it can't be the floor for any normal check.

As for Perception vs Investigation, they are frustratingly similar. The key to separating these is actually in how you present challenges. Perception notices things, Investigation figures them out. If you want more Investigation in your game, call for more INT checks that Investigation applies to. If you have a trap, let the presence and general threat be detected by Perception, but have the actual operation of the trap (what triggers/methods/results exist) be INT (Investigation). A little change to how things are presented can make Investigation a much more often used tool. Be careful, though, that you're not turning traps into 3-check problems -- detect, determine, defeat -- because that increases dramatically the odds of failure. I'd recommend using the Investigate as a setup skill that can apply advantage to the defeat check on a success and disad on a failure (I'm a huge fan of not calling for a check unless there's a consequence, YMMV). Or, as I often do, making detection automatic -- burn marks on the floor and low walls with obvious holes in the ceiling indicates a trap without a roll. Now the players can investigate. A mix of both -- having traps that are well hidden, like in a chest or a fiendishly clever trap, and traps that are clearly visible, makes for some interest and provide some good adventures, especially if an obvious trap is not feasibly disarmed in a simple manner (some traps, like rolling boulder traps, may be hard to disarm, and thus provide a hazard to be worked around, like a pool of lava).

 

[Charlaquin]

Wisdom (Perception): Used to detect direct sensory information about the environment. To spot the trip wire for the trap, feel the draft from the secret door, hear the footsteps of the hidden goblin, etc.

Intelligence (Investigation): Used to make logical deductions based on available information. To figure out what the trap does and/or how to safely disarm it, how to open the secret door, or to deduce where the goblin must be hiding.

Passive checks: Used to represent the average result of a task performed repeatedly over time. One would not be too amiss to think of this as 5e’s version of 3.Xe’s take 10 rule. Many DMs treat passive Wisdom (Perception) and sometimes passive Wisdom (Insight) as “always on,” since a creature with working senses is arguably engaged in the task of using those senses at all times. Personally, I prefer only to apply it when a creature is alert - i.e. not performing another task while exploring or traveling.

 

[iserith]

Inspired by the Cloak of Elvenkind thread, I've finally decided to address my biggest source of confusion in 5e. Almost seven years in, and I still get occasionally confused about when Passive Perception is used in lieu of normal Perception. It seems to me that it would be when walking by secret doors, noticing traps or ambushes—sort of like the elf's ability to notice secret doors in AD&D, but that begs the question of when does "active" Perception get used and why?) Then there's Investigation. When does it come into play instead of using Perception? When I search a desk, am I using Perception or Investigation? Lastly, why are the rules for these things so virtually non-existent?

So, okay comunity, what are your thoughts on the matter? How have you parsed these things? And where upon the rules do you base your interpretation upon?

A passive check is used when the DM wants to resolve a task that is being performed repeatedly and, like all checks, when those tasks have an uncertain outcome and a meaningful consequence for failure. (A DM can also use passive checks to make "secret rolls" but let's set that aside for now. Personally I think that's an unnecessary use.) Thus, a passive Wisdom (Perception) check is used when trying to determine if a character can spot, hear, or otherwise detect the presence of something while engaged in that task repeatedly. But, again, only when this has an uncertain outcome and a meaningful consequence for failure. If a character engages in a task but not repeatedly and there is a meaningful consequence for failure, then that's just a regular ability check.

So the question is when is the character performing this task repeatedly? Normally, it's during combat and travel. The rules say that most creatures stay alert for signs of danger all around in combat. So unless the player has described the character as not doing that or circumstances have aligned such that this is true, the character's passive Wisdom (Perception) check applies. Same goes for travel, which can be measured in feet or miles across minutes or hours. Don't think of this as just cross country journeys or the like - it could easily be movement through a dungeon or other adventure location. A character that is not staying alert for signs of danger, perhaps because by turning his or her attention to other tasks like navigating, drawing a map, tracking, foraging, or similarly distracting activities (as determined by the DM), does not have an uncertain outcome as to noticing a threat - they fail and run afoul of traps or ambushes if they arise. Thus, there is no need for a passive check here. Uncertainty as to outcome is a prerequisite for calling for any ability check.

Notably, a character that is staying alert can also notice secret doors. And this is where Intelligence (Investigation) checks might come in after the secret door is found. A DM can say that opening the mechanism isn't obvious and that figuring it out (depending on the character's approach) might call for Intelligence (Investigation) check. Obviously, if the character pulls all the books on the shelf, for example, and one of them happens to be the lever for the secret door, then no check is required. But this might take more time than deducing the correct book to pull and pulling just that one. Personally, I separate searching for secret doors as a task on par with navigating, drawing a map, tracking, foraging, meaning that you're not alert for danger if you're doing this while moving about the adventure location. This is because in my games secret doors are excellent finds, concealing treasure, short cuts, or safe places to rest. I want that to come at a cost of possibly traps and ambushes.

Intelligence (Investigation) may also come up when the characters are interacting with a trap. Signs of a trap may be apparent in the environment and deducing from the clues that a trap is present might carry with it an uncertain outcome and a meaningful consequence for failure, so a check is appropriate. After finding the trap, figuring out how to disarm it may also call for such a check, effectively creating a way forward for the rogue to do his or her thing or disarming it some other way (or perhaps setting it off safely or avoiding it altogether). If, however, the clues to a trap are hidden objects, then we're back to resolving finding them by way of a Wisdom (Perception) check, again, when there's an uncertain outcome and a meaningful consequence for failure. With clues in hand, the work of deducing what those clues mean can begin.

The rules for these things are there if you look for them in the PHB and DMG. They are often in different parts of the books - Chapters 7 and 8 of the PHB, Chapter 5 of the DMG, plus of course the general rules for adjudication on DMG, page 237 (the holiest page of the DMG). By way of these rules, it is very likely that a given game sees much more use of passive Wisdom (Perception) checks than Intelligence (Investigation) checks. I see nothing wrong with that. The rules do not suggest in any way (that I know) that these should have parity. But certainly if you are including secret doors and traps in your game and are requiring some amount of deduction be undertaken to engage with them, then you will see Intelligence (Investigation) checks come up pretty frequently. A lot of DMs in my experience don't include these elements in their game sadly and so Intelligence (Investigation) checks don't appear much.

 

[DND_Reborn]

First, I like to add references for convenience in such a discussion:

Passive Checks​

A passive check is a special kind of ability check that doesn't involve any die rolls. Such a check can represent the average result for a task done repeatedly, such as searching for secret doors over and over again, or can be used when the DM wants to secretly determine whether the characters succeed at something without rolling dice, such as noticing a hidden monster.

Here's how to determine a character's total for a passive check:

10 + all modifiers that normally apply to the check

If the character has advantage on the check, add 5. For disadvantage, subtract 5. The game refers to a passive check total as a score.

For example, if a 1st-level character has a Wisdom of 15 and proficiency in Perception, he or she has a passive Wisdom (Perception) score of 14.

The rules on hiding in the “Dexterity” section below rely on passive checks, as do the exploration rules in chapter 8, “Adventuring.”

HIDING

The DM decides when circumstances are appropriate for hiding. When you try to hide, make a Dexterity (Stealth) check. Until you are discovered or you stop hiding, that check's total is contested by the Wisdom (Perception) check of any creature that actively searches for signs of your presence.

You can't hide from a creature that can see you clearly, and you give away your position if you make noise, such as shouting a warning or knocking over a vase. An invisible creature can always try to hide. Signs of its passage might still be noticed, and it does have to stay quiet.

In combat, most creatures stay alert for signs of danger all around, so if you come out of hiding and approach a creature, it usually sees you. However, under certain circumstances, the DM might allow you to stay hidden as you approach a creature that is distracted, allowing you to gain advantage on an attack roll before you are seen.

Passive Perception. When you hide, there's a chance someone will notice you even if they aren't searching. To determine whether such a creature notices you, the DM compares your Dexterity (Stealth) check with that creature's passive Wisdom (Perception) score, which equals 10 + the creature's Wisdom modifier, as well as any other bonuses or penalties. If the creature has advantage, add 5. For disadvantage, subtract 5.

For example, if a 1st-level character (with a proficiency bonus of +2) has a Wisdom of 15 (a +2 modifier) and proficiency in Perception, he or she has a passive Wisdom (Perception) of 14.

What Can You See? One of the main factors in determining whether you can find a hidden creature or object is how well you can see in an area, which might be lightly or heavily obscured as explained in chapter 8, “Adventuring.”

Investigation​

When you look around for clues and make deductions based on those clues, you make an Intelligence (Investigation) check. You might deduce the location of a hidden object, discern from the appearance of a wound what kind of weapon dealt it, or determine the weakest point in a tunnel that could cause it to collapse. Poring through ancient scrolls in search of a hidden fragment of knowledge might also call for an Intelligence (Investigation) check.

Perception​

Your Wisdom (Perception) check lets you spot, hear, or otherwise detect the presence of something. It measures your general awareness of your surroundings and the keenness of your senses. For example, you might try to hear a conversation through a closed door, eavesdrop under an open window, or hear monsters moving stealthily in the forest. Or you might try to spot things that are obscured or easy to miss, whether they are orcs lying in ambush on a road, thugs hiding in the shadows of an alley, or candlelight under a closed secret door.

FINDING A HIDDEN OBJECT

When your character searches for a hidden object such as a secret door or a trap, the DM typically asks you to make a Wisdom (Perception) check. Such a check can be used to find hidden details or other information and clues that you might otherwise overlook.

In most cases, you need to describe where you are looking in order for the DM to determine your chance of success. For example, a key is hidden beneath a set of folded clothes in the top drawer of a bureau. If you tell the DM that you pace around the room, looking at the walls and furniture for clues, you have no chance of finding the key, regardless of your Wisdom (Perception) check result. You would have to specify that you were opening the drawers or searching the bureau in order to have any chance of success.

INTELLIGENCE CHECK VS. WISDOM CHECK

If you have trouble deciding whether to call for an Intelligence or a Wisdom check to determine whether a character notices something, think of it in terms of what a very high or low score in those two abilities might mean.

A character with a high Wisdom but low Intelligence is aware of the surroundings but is bad at interpreting what things mean. The character might spot that one section of a wall is clean and dusty compared to the others, but he or she wouldn’t necessarily make the deduction that a secret door is there.

In contrast, a character with high Intelligence and low Wisdom is probably oblivious but clever. The character might not spot the clean section of wall but, if asked about it, could immediately deduce why it’s clean.

Wisdom checks allow characters to perceive what is around them (the wall is clean here), while Intelligence checks answer why things are that way (there’s probably a secret door).

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Inspired by the Cloak of Elvenkind thread, I've finally decided to address my biggest source of confusion in 5e. Almost seven years in, and I still get occasionally confused about when Passive Perception is used in lieu of normal Perception. It seems to me that it would be when walking by secret doors, noticing traps or ambushes—sort of like the elf's ability to notice secret doors in AD&D, but that begs the question of when does "active" Perception get used and why?) Then there's Investigation. When does it come into play instead of using Perception? When I search a desk, am I using Perception or Investigation? Lastly, why are the rules for these things so virtually non-existent?

So, okay comunity, what are your thoughts on the matter? How have you parsed these things? And where upon the rules do you base your interpretation upon?

Ok, so lots of DM run this stuff differently, I so I am going to try to respond as close to RAW as I understand:

• Passive Perception is used for a) routine activities repeated often and b) when the DM wants something done in secret without asking for a roll.
• Passive Perception is used when a creature might notice something without actively looking.
• Active Perception is used when a player (given the scenario) has cause to have their PC actively search for something. This gives them the chance to roll higher than the default "passive" 10 so the PC can notice something which has a higher DC.
• Investigation is used to understand the significance of something, whether it is finding a clue and understanding why it is important, recognize a difference in handwriting on a document, realizing a book is out of place and opens a hidden compartment, etc.

For myself, I like to think of things like this: Perception is Awareness, Investigation is Understanding.

This is why I can rule a rogue might make a WIS (Perception) to uncover a hidden trap, INT (Investigation) to figure out how to disarm it, and then DEX (Thieves' Tools) to disable the trap.

I treat the Passive Perception score as meaning, if the player does not say their PC is "observing or searching", that the PC might notice something even if they player doesn't ask to make a check. If the passive score is high enough, I will tell the player to make a WIS (Perception) check to see if the PC is successful. I don't like the idea that passive scores can be automatic--it is too good IMO.

Ex. A ranger has a passive perception score of 16. Hiding nearby is a group of goblins which made a DEX (Stealth) check of 15. The player has not said the ranger is actively on guard or anything, but with such a decent passive perception, I know the PC might detect the goblins anyway. So, I will tell the player to roll for the ranger. If the roll beats the goblins' stealth, the ranger spots the ambush, otherwise the ranger will be surprised.

RAW, the ranger would automatically know the goblins are there. Personally, I don't like that, so I run it a bit differently. IF I wanted it to be automatic, I would make passive 5+ modifiers, not 10+ modifiers.

 

[Shiroiken]

Perception is supposed to be noticing thing, while Investigation is understanding the importance of noticed things. Technically this should be mean that most things would require two checks, such as perception to see the trigger for the trap and investigation to realize it's the trigger for a trap. This really isn't ideal, however, so pretty much everything seems to get lumped into perception. Because of this, in my game I use perception for finding hidden creatures and investigation for hidden oddities (such as traps and secret doors). Creatures just need to be seen to be understood, but even if you notice something odd, you'd have to understand what it means.

Passive skills are poorly understood because they never actually put the rules down on how to use them. I'm of the opinion that this was intentional in order to allow each group to decide how to use them, despite JC's insistence on how they're "the floor" for those skills. I use the Mike Mearls of method of rolling a die against the PCs passive skill, allowing a level of randomness while still rewarding spending resources on passive bonuses. One nice thing about this is that you can then expand the passive skills to include the knowledge skills (arcana, history, etc.) so that you can roll a passive check to give out some info before the players think to ask.