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

billd91

Hobbit on Quest
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.
This is one instance where pulling more from 4e might have helped. Here's what the 4e PH has to say:

4e Players Handbook said:
Checks without Rolls
In some situations, luck does not affect whether you succeed or fail. In a calm environment (outside an encounter), when dealing with a mundane task, you can rely on sheer ability to achieve results.
Take 10
When you’re not in a rush, not being threatened or distracted (when you’re outside an encounter), and when you’re dealing with a mundane task, you can choose to take 10. Instead of rolling a d20, determine your skill check result as if you had rolled the average (10). When you take 10, your result equals your skill modifiers (including one-half your level) + 10. For mundane tasks, taking 10 usually results in a success.
Passive Checks
When you’re not actively using a skill, you’re assumed to be taking 10 for any opposed checks using that skill. Passive checks are most commonly used for Perception checks and Insight checks, but the DM might also use your passive check result with skills such as Arcana or Dungeoneering to decide how much to tell you about a monster at the start of an encounter.
For example, if you’re walking through an area you expect to be safe and thus aren’t actively looking around for danger, you’re taking 10 on your Perception check to notice hidden objects or enemies. If your Perception check is high enough, or a creature rolls poorly on its Stealth check, you might notice the creature even if you aren’t actively looking for it.

5e largely dispenses with the need for a player to Take 10 by giving the DM the authority to declare success/failure outright when the outcome shouldn't really be in doubt. The passive check description here is, I think, nice and clear - clarity of the rules being one of 4e's general strengths. And notice the idea of passive knowledge checks here as well, one of the reasons why I'm specifically responding to your post, Shiroiken.
One drawback to the whole Taking 10/passive score issue, however, is the rules for them developed in editions where opponents who were level-appropriate were likely to keep up with a PCs skill value, making Taking 10/passive checks less of a likely success. They were great for weaker opponents, relatively mundane challenges but deliberately accepted a half-assed result that left half of the d20's results, the higher half, completely out of reach. PCs couldn't count on a lucky die roll to find a particularly challenging skulker or trap. That doesn't seem to be as likely with 5e with more PCs likely to be proficient in perception compared to monsters significantly skilled in stealth, or vice versa. The passive perception score tends to do really well by comparison.
 

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Charlaquin

Goblin Queen
This is one instance where pulling more from 4e might have helped. Here's what the 4e PH has to say:



5e largely dispenses with the need for a player to Take 10 by giving the DM the authority to declare success/failure outright when the outcome shouldn't really be in doubt. The passive check description here is, I think, nice and clear - clarity of the rules being one of 4e's general strengths. And notice the idea of passive knowledge checks here as well, one of the reasons why I'm specifically responding to your post, Shiroiken.
One drawback to the whole Taking 10/passive score issue, however, is the rules for them developed in editions where opponents who were level-appropriate were likely to keep up with a PCs skill value, making Taking 10/passive checks less of a likely success. They were great for weaker opponents, relatively mundane challenges but deliberately accepted a half-assed result that left half of the d20's results, the higher half, completely out of reach. PCs couldn't count on a lucky die roll to find a particularly challenging skulker or trap. That doesn't seem to be as likely with 5e with more PCs likely to be proficient in perception compared to monsters significantly skilled in stealth, or vice versa. The passive perception score tends to do really well by comparison.
I actually rather think that looking to how 4e handled passive checks causes undue confusion. Passive checks in 4e were used for resolving opposed checks when you aren’t actively using a skill. Conversely, so-called passive checks in 5e are explicitly for use when a task is being performed repeatedly over time.

Certainly, one can choose to run passive checks in 5e more like how they were used in 4e, but I believe that is quite the opposite of how the rules describe them.
 

Xetheral

Three-Headed Sirrush
Personally, I use a couple of houserules to avoid some of these issues.

First, I let Observant give advantage on active Perception and Investigation checks, in addition to passive checks. I do this because I don't want the utility of the feat to depend heavily on whether I call for an active check or use a passive check. (As a general principle, I don't want the outcome of an in-game action to be dependent on the choice between two different resolution methods.)

Second, in addition to deduction, I let Investigation also apply to situations covered by the old Gather Information skill, and I also let it work as a general-purpose Research skill (broader than just finding hidden fragments of knowledge). I find this gives the Investigation skill enough alternative uses that I don't have to go out of my way to design traps and other game elements in a way that makes Investigation useful--instead I can just design traps with the builder's IC goals/resources in mind.
 

billd91

Hobbit on Quest
I actually rather think that looking to how 4e handled passive checks causes undue confusion. Passive checks in 4e were used for resolving opposed checks when you aren’t actively using a skill. Conversely, so-called passive checks in 5e are explicitly for use when a task is being performed repeatedly over time.
Honestly, those are pretty much the same thing. You're never not perceiving the world around you, giving you a chance to spot some hostile creature stalking you. When someone is lying to you, you're never not observing them and capable of judging whether or not they're lying. You just may not be putting as much focus into it (hence, giving up the upper half of the d20's potential results) as when you're actively engaging in it.
What the 4e rules do is indicate fairly clearly when the passive score is used vs when the rolled result is used. The passive isn't a floor to use if the actively used check comes up low on the d20.
 

Charlaquin

Goblin Queen
Honestly, those are pretty much the same thing.
I don’t think they are at all. In 4e, use of passive checks is automatic and applied when you aren’t using the skill actively. In 5e, use of a “passive” check is specifically called for by the DM when a task is performed over and over again (and has a risk of and consequence for failure.) It is much closer to 4e’s version of taking 10 than to 4e’s passive check.
You're never not perceiving the world around you,
giving you a chance to spot some hostile creature stalking you. When someone is lying to you, you're never not observing them and capable of judging whether or not they're lying. You just may not be putting as much focus into it (hence, giving up the upper half of the d20's potential results) as when you're actively engaging in it.
Well, as someone with ADHD who is constantly on their phone (mostly using it to post on gaming forums), I disagree that you’re always aware of the world around you. But, setting that aside, if you do want to use that as a basis to form your ruling on passive perception, that’s fine, but I don’t think it’s consistent with how the rules of 5e describe using them.

What the 4e rules do is indicate fairly clearly when the passive score is used vs when the rolled result is used. The passive isn't a floor to use if the actively used check comes up low on the d20.
Right, but I think the 5e rules describe how to use passive checks quite clearly as well, it just happens to be different than how the 4e rules describe using passive scores. The only thing that’s unclear about passive checks in 5e is that the name doesn’t really line up well with how the rules say to use them. I think if they had called the rule “taking 10” instead, no one would find it confusing at all.
 
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iserith

Magic Wordsmith
Personally, I use a couple of houserules to avoid some of these issues.

First, I let Observant give advantage on active Perception and Investigation checks, in addition to passive checks. I do this because I don't want the utility of the feat to depend heavily on whether I call for an active check or use a passive check. (As a general principle, I don't want the outcome of an in-game action to be dependent on the choice between two different resolution methods.)

Second, in addition to deduction, I let Investigation also apply to situations covered by the old Gather Information skill, and I also let it work as a general-purpose Research skill (broader than just finding hidden fragments of knowledge). I find this gives the Investigation skill enough alternative uses that I don't have to go out of my way to design traps and other game elements in a way that makes Investigation useful--instead I can just design traps with the builder's IC goals/resources in mind.
For Observant, I run it as written, but the key thing is that in my games, if you want to be the guy or gal who notices all the threats (monsters, traps), that's the only task you're doing, unless you're a ranger in favored terrain. You can't navigate, draw a map, forage, track, or search for secret doors. I take care to ensure that these activities are valuable in context so that there's a meaningful choice as to what to do. Source maps are worth gold. Navigating keeps the party from getting lost and going off course. Foraging keeps food and water stocked or turns up valuable trade goods. Tracking allows the party to look for trouble (XP!) or avoid it. Secret doors always lead to treasure, short cuts around dangers, or safe places to rest. So yeah, be Observant, whip out that 20+ PP! But know that you probably won't be doing this other stuff. Plus depending on your marching order, you might not be able to notice threats at the front of the party unless you're in the front rank. That means you're likely the meat shield for people behind you.

I think a character trying to influence locals to giving up useful information would be fine for a Charisma check and a player establishing the character is working to deduce who to talk to and what the rumors all mean could be a Charisma (Investigation) check, if a check was called for. I find I don't have to go out of my way to design traps and secret doors though because that's firmly in the scope of Dungeons & Dragons anyway.
 

Charlaquin

Goblin Queen
Personally, I use a couple of houserules to avoid some of these issues.

First, I let Observant give advantage on active Perception and Investigation checks, in addition to passive checks. I do this because I don't want the utility of the feat to depend heavily on whether I call for an active check or use a passive check. (As a general principle, I don't want the outcome of an in-game action to be dependent on the choice between two different resolution methods.)
I think this issue could also be resolved by being very consistent with when you call for rolls vs. when you call for passive checks, and being very transparent with the players about when you use each. Not that the house rule isn’t also a good one of course. I might go for advantage on rolled checks instead of +5 on them, but the concept is solid.
Second, in addition to deduction, I let Investigation also apply to situations covered by the old Gather Information skill, and I also let it work as a general-purpose Research skill (broader than just finding hidden fragments of knowledge). I find this gives the Investigation skill enough alternative uses that I don't have to go out of my way to design traps and other game elements in a way that makes Investigation useful--instead I can just design traps with the builder's IC goals/resources in mind.
I call for ability checks and let the player determine if any of their proficiencies are applicable. But I do think there are a lot of information gathering and research related tasks where investigation proficiency seems like it would be very applicable.
 


Xetheral

Three-Headed Sirrush
For Observant, I run it as written, but the key thing is that in my games, if you want to be the guy or gal who notices all the threats (monsters, traps), that's the only task you're doing, unless you're a ranger in favored terrain. You can't navigate, draw a map, forage, track, or search for secret doors. I take care to ensure that these activities are valuable in context so that there's a meaningful choice as to what to do. Source maps are worth gold. Navigating keeps the party from getting lost and going off course. Foraging keeps food and water stocked or turns up valuable trade goods. Tracking allows the party to look for trouble (XP!) or avoid it. Secret doors always lead to treasure, short cuts around dangers, or safe places to rest. So yeah, be Observant, whip out that 20+ PP! But know that you probably won't be doing this other stuff. Plus depending on your marching order, you might not be able to notice threats at the front of the party unless you're in the front rank. That means you're likely the meat shield for people behind you.

I think a character trying to influence locals to giving up useful information would be fine for a Charisma check and a player establishing the character is working to deduce who to talk to and what the rumors all mean could be a Charisma (Investigation) check, if a check was called for. I find I don't have to go out of my way to design traps and secret doors though because that's firmly in the scope of Dungeons & Dragons anyway.
That's cool. Thanks for sharing!

Personally, I find my houserules helpful at my table partially because I run a very player-driven, game with a heavy emphasis on simulation. (Those two go together--the heavy emphasis on simulation makes the game world more predictable, which in turn gives the players more agency to control their influence on the game world.)

So some of the techniques you use at your table to make the written rules work well are less usable/relevant at my table. Unless the party has screwed up somehow and lost the strategic initiative, there are rarely hidden threats for them to notice: they are the threat. Sure, there might occasionally be a group of bandits trying to ambush whomever comes next along the road,* but deliberate ambushes are rare, unless the PCs have let their enemies know when and where they'll be. Keeping alert while travelling is still invaluable, but I suspect there are fewer potentially hidden threats to notice at my table than at yours. Similarly, secret doors will rarely lead to treasure or places to rest at my table (they're more likely to be emergency exits, spyholes, or mere conveniences), the party will often already have purchased a map (trying to plan encounters strategically is a lot harder if you don't already know the terrain) or talked to locals in advance to get the lay of the land, and tracking isn't a source of XP since I don't award XP per-fight. (Also, XP is a purely OOC concept at my table, so seeking it out IC would be frowned on.)

(*And unless they're desperate or stupid, the bandits probably aren't going to attack a small, heavily armed group. Such targets are often dangerous, and unlikely to have much in the way of trade goods or easily marketable loot. Sure, some PCs carry godly amounts of cash, but the bandits don't know that.)

And my emphasis on simulation makes some of the abstraction in the written rules less palatable. I don't want players of Observant characters to feel like they have to deliberately frame their action declarations as a repeated task so that they can get a Passive-check-only bonus--it feels artificial and thus hampers verisimilitude. For example, why should an Observant trapfinder be better at searching for traps repeatedly than she is at searching for traps one at a time? Given my style preferences, I'd rather houserule than handwave that inconsistency.

As far as investigation, I do find myself having to go of my way to makes traps that require investigation of their mechanisms. Likely, that's because my emphasis on simulation means I'm usually going to use very simple traps that would be very easy for whomever built them to afford, and the mechanism of such traps are simple to understand. Traps with obscure mechanisms would be rare and expensive, and if well-designed would be impossible to notice in advance. Sure, I can come up with plausible explanations for badly designed (i.e. noticable) traps with complicated mechanisms, but I'm not going to do that just to make Investigation proficiency useful: I'd rather just houserule in expanded uses for the skill.

In the end, I know I'm not running a typical game. While I firmly believe my style of play was intended to be (and is!) supported by 5e, since it's not a common style I expect to need to houserule on occasion. Hence, my houserules for Observent and Investigation. They're broad enough that they could be useful in a variety of playstyles, so I shared them in case anyone concerned with the issues discussed in this thread find them a palatable solution.
 




All of this confusion and complexity around perception (and it's been going for multiple editions now) is due to a fundamental flaw in D&D:

Perception should be an attribute. Whether it should be a 7th attribute, or it should replace wisdom (which I favour), it's lack is a deep flaw in the system. I know a lot of people regard the six attributes are a sacrosanct part of the game, but for me it's a sacred cow that I'd be happy to see killed.
 

Charlaquin

Goblin Queen
All of this confusion and complexity around perception (and it's been going for multiple editions now) is due to a fundamental flaw in D&D:

Perception should be an attribute. Whether it should be a 7th attribute, or it should replace wisdom (which I favour), it's lack is a deep flaw in the system. I know a lot of people regard the six attributes are a sacrosanct part of the game, but for me it's a sacred cow that I'd be happy to see killed.
I mean, Wisdom is functionally the perception attribute in 5e. It encompasses interpersonal awareness as well as sensory awareness, but that’s what its uses cover.
 

billd91

Hobbit on Quest
I don’t think they are at all. In 4e, use of passive checks is automatic and applied when you aren’t using the skill actively. In 5e, use of a “passive” check is specifically called for by the DM when a task is performed over and over again (and has a risk of and consequence for failure.) It is much closer to 4e’s version of taking 10 than to 4e’s passive check.
That still is pretty much the same thing. The whole idea that you're making discrete tasks again and again rather than the skill being exercised without actively focusing on it is a distinction without a reasonable difference. You pretty much have to be doing something particularly distracting to not get it. Everyone else, even in the somewhat bizarre division of duties in overland travel, who isn't doing something specific has it going by default.
 

robus

Lowcountry Low Roller
Supporter
All of this confusion and complexity around perception (and it's been going for multiple editions now) is due to a fundamental flaw in D&D:

Perception should be an attribute. Whether it should be a 7th attribute, or it should replace wisdom (which I favour), it's lack is a deep flaw in the system. I know a lot of people regard the six attributes are a sacrosanct part of the game, but for me it's a sacred cow that I'd be happy to see killed.
I’m not sure that’s necessary. If we look at animal stat blocks we see they generally have high wisdom scores and low intelligence scores. With that in mind we can extrapolate that perception (a wisdom skill) correlates to examining the natural world and noticing things that are out of place: a strange odor, an odd noise, a breeze in a enclosed area, a mismatched thing. Basically something that triggers a “that’s odd” response.
 

Umbran

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

This is reasonable, with one caveat.

Unless you are really good at writing mysteries, as a GM, you are probably not actively and explicitly describing the world in enough detail to distinguish between the cases much of the time.

I am currently running a gnomish artificer who took the Observant feat. End result is that he's got a passive Investigation score of 23. The character is basically Sherlock Holmes - by the stats he should be able to walk into a place, and without breaking a sweat, rattle off seven details in plain sight that add up to the fact that the killer is hidden behind the arras, and be correct.

The character is smarter than either myself, or the GM. The character lives in the world 24/7, but neither the GM or I do. The character's abilities a putting 2 nd 2 together to get 4 exceed our abilities at creating these chains of clues. So, the GM just generally assumes that outside of combat he can use Investigation, and only cases in which the DC is for some specific and knowable reason very high, does he not notice.
 

6ENow!

The Game Is Over
This is reasonable, with one caveat.

Unless you are really good at writing mysteries, as a GM, you are probably not actively and explicitly describing the world in enough detail to distinguish between the cases much of the time.

I am currently running a gnomish artificer who took the Observant feat. End result is that he's got a passive Investigation score of 23. The character is basically Sherlock Holmes - by the stats he should be able to walk into a place, and without breaking a sweat, rattle off seven details in plain sight that add up to the fact that the killer is hidden behind the arras, and be correct.

The character is smarter than either myself, or the GM. The character lives in the world 24/7, but neither the GM or I do. The character's abilities a putting 2 nd 2 together to get 4 exceed our abilities at creating these chains of clues. So, the GM just generally assumes that outside of combat he can use Investigation, and only cases in which the DC is for some specific and knowable reason very high, does he not notice.
This is why I treat passive scores the way I do.

As a DM, if I know there is a clue or something a PC might notice, but I don't describe well enough or the player isn't clever enough to connect the dots, I use passive scores. For example, if the DC is 20, and your gnome with a 23 should fine something, I'll ask you to roll. That is not RAW, of course, but I don't want auto-successes. With +8, you have a good chance of making it so I'll let the dice decide.

I also think that because distinguishing between them is often difficult and/or blurred--it should be a single skill, but used with either INT or WIS depending on the bent employed in the situation.

But yeah, Observant can led to really high passive scores. In our 1-20 campaign, my rogue with INT and WIS 18 and Observant had Passive Perception (and Investigation) scores of 31 at level 20. Not the highest possible, but pretty darn good. ;) The sad thing is, with Reliable Talent, the lowest I could even roll was 26s...

At any rate, if passive scores are really "passive" and not "averages or taking 10s" (which they more seem to be), I think they should be 5+modifiers, and Observant would then boost them to 10+ effectively.
 

pming

Hero
Hiya!
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?

DM: "You travel down the 5' wide stone corridor. The walls are slick with water and slimy-moss, the floor, even worse." [secret door here with DC 14; looks at PC's Passive Perception of 12]
Player: "OK, I'll keep walking, but at half rate to keep my footing"
DM: [thinking that moving at half rate is worth a +2 to Passive Perception] "At about 40' down the corridor, something catches your attention. A section of the wall on you right, about 9 or 10 feet of it, seems to have less of that slimy-moss on it"
Player: "Really? Hmmm...I'll stop and raise the lantern a bit to get a better or closer look...do I notice anything?"
DM: "What's your Perception?"
Player: "It's +2"
DM: "Right...[rolls d20, gets 17, +2 is 19]. Now that you are looking, you notice that there are distinct 'lines', pretty much straight, on the left and right of a 6' section. The floor here, by that section, also seems to be cleared of most slime...not nearly as thick. Probably some kind of Secret Door"
Player: "Ha! Ok, I'm going to start looking for bricks or rocks in the wall that are different colours, or smoother, or something. I'm looking to see if it can open from this side"
DM: "You press various rocks that catch your attention...what's your Investigation? Make a check for me..."
Player: "Ok...I got a total of... 15"
DM: "That'll do it! There are two rocks, one on the door, one on the wall next to it; pressing both at the same time results in a satisfying 'CLICK!' and the door opens towards you about one inch. The smell of rotting flesh spills out, choking your nostrils and throat....what are you doing now...?"
..
That is how I run Passive and Active Perception, and Investigation.
Passive it to "notice something that gets your attention". Active when you try and discern what it was that grabbed your attention. Investigation is when you find out exactly what grabbed your attention and now you want to do something about it.

Oh, and yeah, I tend to roll the PC's Active Perception checks. Sometimes others as well, when the binary high/low of the system would give too much info away (re: "Make a Perception"... "Whoot!, with my silly adjustment I have 28!"... "Oh. Uh...you don't notice anything" ... "Cool guys! This area is totally safe...lets camp!" ;)

..
^_^

Paul L. Ming
 

Umbran

Mod Squad
Staff member
This is why I treat passive scores the way I do.

As a DM, if I know there is a clue or something a PC might notice, but I don't describe well enough or the player isn't clever enough to connect the dots, I use passive scores.

So, here's the point I was trying to make: The litmus test, at least in this game, is not "does the GM know there is a clue", but instead, "does the GM expect there might be a clue, whether the GM specifically placed it or not".

We are talking about an excessive case to make the point that the idea that only that which the GM describes is relevant is kind of bogus. Because the GM gives, at best, a sketch of the room, with minimal details. But the PCs should see it in 4k HD, right?

Say the characters are exploring a building. There's a workroom, and hearing the PCs approach, the man in the room hides behind a tapestry. The PCs enter.

The GM can think of the old cliche that the tea in the pot is still warm, from which the PCs can conclude that the person was here recently. But there's probably 17 other indicators that the man likely left behind - boots still by the door, wet ink on a parchment, the quill not put away, the way a chair is subtly turned as the man got up quickly, the little trickle of blotting sand on the floor... which all indicate the man is still here and where he went.
 

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