D&D 5E Perception vs Investigation

[pukunui]

Hi folks,

After reading through the AL preview version of Princes of the Apocalypse, I got the feeling that WotC/Sasquatch is just as confused about when to use Perception or Investigation as I am.

The PHB seems to indicate that you use Perception to detect things like secret doors and whatnot, whereas Investigation is more for piecing together clues, rather than just being a fancily renamed Search.

However, the use of these two skills was somewhat unclear in Lost Mine of Phandelver. Sometimes something that required a Perception check in one part of the adventure would later require an Investigation check elsewhere.

I have only ever skimmed through the Tyranny of Dragons adventures, so I can't speak to how the skills are used in them, but I can say that it appears that in Princes of the Apocalypse, finding secret doors and false bottoms in chests and the like requires Investigation rather than Perception.

I reckon Jeremy needs to do a Sage Advice column on this.

Cheers,
Jonathan

 

[Paraxis]

A perception check or passive perception might alert you to something being off or strange about a bookcase but it takes an investigation check to reason out how to open it. Same for investigating a chest for a false bottom.

Perception: alerts you to the presence of things that might go unnoticed, like creatures trying to hide from you or a scuff mark on the floor by a sliding bookcase.

Investigation: allows you to use deductive reasoning that the room is smaller on the inside than the outside would suggest, or if the bookcase slides open as opposed to the mover just scuffing up the floor when it the furniture was rearranged.

I think a lot of the confusion is that players seem to think they should just roll checks or ask to make checks like clicking a button on a character sheet. The players should describe their actions and interactions with the environment and the DM calls for the proper check depending on the situation. Some of those checks might not even be rolled by the player, but by the DM, especially checks like perception and investigation.

 

[MerricB]

It's a little clearer in the DMG, but I agree - the definitions in the PHB are really, really bad.

Perception allows you to notice something is wrong.
Investigation allows you to determine what is wrong.

In the case of traps, Perception allows you to notice that there's something wrong about the area - less travelled, strange holes, that sort of thing.
Investigation allows you to discover a pit trap or a flame jet or whatever, with a little searching.

In this case, you can only attempt a disarm check if you've succeeded at an Investigation check first.

However, that may not be what's intended.

I'm very tempted to instead of putting in an Investigation or Perception DC to instead have a "Detect DC" and let individual DMs work out what skill applies. I'd appreciate any thoughts on this!

Cheers!

 

[pukunui]

A perception check or passive perception might alert you to something being off or strange about a bookcase but it takes an investigation check to reason out how to open it. Same for investigating a chest for a false bottom.

Yeah, that's how I've been running it.

It's just that the inconsistency between the rules in the PHB and the way they're applied in the official adventures irks me.

I think a lot of the confusion is that players seem to think they should just roll checks or ask to make checks like clicking a button on a character sheet. The players should describe their actions and interactions with the environment and the DM calls for the proper check depending on the situation. Some of those checks might not even be rolled by the player, but by the DM, especially checks like perception and investigation.

There is that, yes, but I'm talking more about what skills are being called out in the adventures. In LMoP, there are secret doors and traps and such, some of which the text says require a Perception check, while others require an Investigation check. There's also some inconsistency relating to active vs passive Perception in that adventure.

In PotA, on the other hand, the text just says that an Investigation check is needed to find a secret door or whatever.

My point being that the official adventures aren't consistent and don't offer that dual-check option (The entry for a secret door could indicate that a Perception check would let you know there's something there while an Investigation check is required to find out what it is, for instance).

I'm very tempted to instead of putting in an Investigation or Perception DC to instead have a "Detect DC" and let individual DMs work out what skill applies. I'd appreciate any thoughts on this!

That definitely has potential!

 

[iserith]

Figuring out how to open a secret door or the like can be resolved an Investigation check when doing so has an uncertain outcome. Detecting the secret door or the like is still a Wisdom (Perception) check. See DMG, page 103-104. I haven't read the module you're referencing, but I don't doubt that sometimes the designers get this "wrong."

I find this all becomes a lot easier to adjudicate when the DM keeps two things in mind: (1) The need to telegraph when describing the environment and (2) that we only call for rolls when we think the character is doing something with an uncertain outcome. Not every action calls for a check.

Investigation: When you look around for clues and make deductions based on those clues, you make an Intelligence (Investigation) check.

Perception: Your Wisdom (Perception) check lets you spot, hear, or otherwise detect the presence of something.

As we can see here, the key difference is clues. Investigation does not deal with detecting the presence of clues per se - it deals with deducing things from the clues you have in hand if said deduction is not a certainty. If the clues are hidden, then their presence is detected via Perception if detecting them is uncertain. If you're telegraphing, that means you're providing clues to the players (or suggesting there may be hidden clues) from which they can draw conclusions when they have them in hand. Oftentimes, a player will simply draw conclusions on his or her own and act accordingly, thereby skipping the need for an Investigation check. A good practice when playing, however, is to state, "Chuck Dagger considers what these clues mean and tries to deduce whether [player's theory] is correct..." as a means to confirm the validity of a conclusion the player has drawn. This way you're mitigating the chance you're acting on assumptions that are incorrect. It's also a good action to describe when you've got the clues but you can't put two and two together - but maybe your character can.

At the end of the day though? It probably doesn't amount to much to get this "wrong." It comes down to how you're describing your scenes and whether or not the actions described by the players have an uncertain outcome. Consider describing the environment in an interesting way that invites the players to engage with the exploration pillar by telegraphing threats and clues. In the doing, you will encourage players to make deductions about their environment and take actions accordingly. They can therefore sometimes rob randomness of its power and solve for X without ever needing to roll a die.

 

[pukunui]

but I don't doubt that sometimes the designers get this "wrong."

Yes, and that's what I'm complaining about here. On the one hand, you've got (poor) instructions on how to use these skills in the rules, while on the other, you have inconsistent application of the skills in the adventures.

Examples:

*In the Redbrand Hideout in LMoP (pg 20), the secret doors can be found either with a high enough passive Perception score, or with a successful active Perception check by "a character who takes the time to search the wall" in the right area.

*In the AL preview of PotA, there is a secret door in the Tomb of Moving Stones (pg 28) that requires a successful Investigation check to find "by noticing the unmortarted stone outlining the door".

 

[Paraxis]

It's just that the inconsistency between the rules in the PHB and the way they're applied in the official adventures irks me.

There is that, yes, but I'm talking more about what skills are being called out in the adventures.

My point being that the official adventures aren't consistent and don't offer that dual-check option.

Agree the published adventures have not gotten this area right, hopefully it will be fixed in the future.

Perception allows you to notice something is wrong.
Investigation allows you to determine what is wrong.

Perfect, and succinct.

I'm very tempted to instead of putting in an Investigation or Perception DC to instead have a "Detect DC" and let individual DMs work out what skill applies. I'd appreciate any thoughts on this!

This is a very good solution, the DC's should probably be the same in most situations anyway.

The only other way to handle it would be to call out what each does.

Wis(Perception) DC 10: There are gouges in the stone wall ahead.
Wis(Perception) DC 15: A stone in the far wall past the gouges seems discolored.
Int(Investigation) DC 15: There is a scythe blade trap, it will be difficult to disarm, but there should be a control somewhere nearby to disarm it with ease.

To disarm the trap is a DC 20 in the hall, at the hidden panel behind the fake stone it is DC 10.

 

[pukunui]

The only other way to handle it would be to call out what each does.

Wis(Perception) DC 10: There gouges in the stone wall ahead.
Wis(Perception) DC 15: A stone in the far wall past the gouges seems discolored.
Int(Investigation) DC 15: There is a scythe blade trap, it will be difficult to disarm, but there should be a control somewhere nearby to disarm it with ease.

To disarm the trap is a DC 20 in the hall, at the hidden panel behind the fake stone it is DC 10.

I know it would eat up more space in the adventure, but I would very much like them to do something like this (if they don't end up having a generic "detect DC" like Merric is suggesting).

 

[Jester David]

I tend to view Perception vs Investigation as Doctor Watson vs Sherlock Holmes. The former is an army doctor with good eyes and quick to react to danger. The latter is observant and pays attention to what he sees.

 

[iserith]

Yes, and that's what I'm complaining about here. On the one hand, you've got (poor) instructions on how to use these skills in the rules, while on the other, you have inconsistent application of the skills in the adventures.

Examples:

*In the Redbrand Hideout in LMoP (pg 20), the secret doors can be found either with a high enough passive Perception score, or with a successful active Perception check by "a character who takes the time to search the wall" in the right area.

*In the AL preview of PotA, there is a secret door in the Tomb of Moving Stones (pg 28) that requires a successful Investigation check to find "by noticing the unmortarted stone outlining the door".

Don't get me started - the designers appear to be confused about what "passive" refers to in "passive checks" as well (it refers to "no rolling" not that the character isn't actively doing something) from time to time, not to mention conflating Perception and Investigation. Chalk it up to DMs bringing their own personal understandings to the adventure design without a strong central person telling them, "No, that's how we did it in 3.Xe. You need to do it this way now."

Do it the way you think is best and suits your table.