Investigation vs Perception - Comparing Skill Checks
Header Art: Dungeon Master’s Guide (2008) by Wizards of the Coast
One of the big questions I get from my players when I’ve called for an Investigation check was if they could use Perception instead. I see this problem in a lot of places, from forums to actual plays and even in official adventures. Often Investigation gets forgotten about in favor of Perception, mostly because Perception is a Wisdom score and Investigation is an Intelligence score. You are, probably, going to have a higher Wisdom than Intelligence score, and thus a higher Perception than Investigation skill.
Most people think of Perception as the skill for seeing things, which it isn’t really for that. Sure, you can see things with this skill, just like you can hear things, taste things, feel things, and more. But what it doesn’t help you do is understand what you are seeing, feeling, tasting, or hearing. Just cause you can see something, doesn’t mean you understand its significance, what it does, or what all the pieces of the whole mean when put together. Oftentimes, that will fall onto Investigation, or another Intelligence-based skill like Arcana, Religion, and more.
In fact, I often use Perception and Investigation together, allowing players to find odd clues or hints of traps and secret doors, but not knowing how they function without an Investigation check. This is like when you call for a Perception check to notice a god’s symbol carved into the floor and then ask for a Religion check to know what that symbol is.
You wouldn’t use Perception in place of Religion, just like you shouldn’t use Perception in place of Investigation.
Investigation
At this point, you are probably wondering, in the analogy above, what is the Investigation skill the ‘Religion’ of? Simply put, anything mechanical or finding knowledge hidden away.
The more complicated answer is that you should call for an Investigation check whenever a character must rely on logic, complex solutions, or deductions. When they Investigate, they are scouring through clues and hints trying to put together a puzzle and learn how it works or what it all means.
For example, just because a character notices that a stone in the floor is slightly raised does not mean that they automatically know it's a trap or how it is supposed to function. While they can certainly assume it is a trap, they won’t know for sure until they go and Investigate it.
Perception
Now that we understand what Investigation does, we can turn our attention to this skill. Perception is a character’s general awareness of the surrounding area. A character that has a higher Perception modifier means that they are going to be more aware of breaks in a pattern, odd sensations that don’t match their surroundings, or detecting something off in the food they just ate.
They don’t automatically know what is weird, off, or triggering senses, but rather they know something is wrong. If they want to know exactly what is wrong, they have to then use their other skills to determine what is wrong and try to understand it then.
For example, a character drinks a poisoned goblet of wine and notices something about its flavor tastes off. Maybe it's bad wine, a wine that has soured, a strange vintage of fae grapes, or its poison. The character could then use Nature or, maybe, Poisoner’s Tools to try and determine if the flavor they are tasting is dangerous to them.
Using the Two Skills
With new understanding, let’s go over a few examples of when you should use Perception and when you should use Investigation - but… before we begin, I’ll just say that this is my personal opinion and stems from my desire to ensure that every skill gets a chance to shine and that a single skill doesn’t become the only skill to take.
Scouring a Library for a Book
In this example, the character is looking for a specific book in a library, and once they find it, need specific information from it. This library is vast, large, and may even be located in a far-flung plane where knowledge itself is stored.
To begin, a character could make a Perception check to find the right section of the library to search in (or use a Charisma skill to convince the librarians to tell them which section). Once they arrive, they now need to scan the shelves for the specific book they need. This could either be Investigation, to read the titles and make an educated guess as to what is in each book, or Perception to read the book titles from a distance and help expedite the search. Once they find the book, they must then make an Investigation check to read through the book and find the hidden information in.
In this example, we use Perception to find something far away (the appropriate library section or to read the book titles from a distance) and then used Investigation to understand what we were reading (gauging what is in each book or searching for hidden information in the book).
Noticing a Trap/Secret Door
Our example begins with our character walking down a long hallway that has stone walls, floors, and a wooden ceiling. They have seen kobolds about and thus are on guard for their kobold-shenanigans.
As the character walks down the hallway, they use their Perception (or their passive Perception as it were) to notice that one of the stone blocks ahead of them just doesn’t seem right. Maybe it's raised a bit too much or looks newer than the others. Upon noticing that, they wish to try and understand what is going on so they then make an Investigation check to crouch down near the tile, notice that the tile depresses when they apply only a few pounds of weight to it, and the ceiling seems to creak ever so slightly as if there is a mechanism within it. They realize that the stone tile is a trap that will collapse the ceiling overhead.
Our character used their Perception to sense something odd in a stone hallway (the tile was slightly raised), they then relied on their Investigation to figure out why the stone tile is raised (it is a pressure plate that would collapse the ceiling).
We can also apply this same logic to a secret door. Sure, they notice that the secret door has seams with a high enough Perception, but they don’t know how to unlock the secret door without a successful Investigation check to know they have to pull a nearby torch sconce.
If things are obvious, like the trap is just a painted tarp over a pit filled with stakes, then there is no need for the Investigation check because it doesn’t require deductive reasoning.
Noticing Hidden Creatures
The character is in a fight for their life against a creature that keeps going invisible every round. They need to know where it is so they can properly fight it.
In this situation, the character will rely on their Perception to notice odd movements in the air, as well as to hear where the enemy is and how far away they are. They only use their primary senses to find the creature and do not need to use deductive reasoning to understand where the creature is as they can sense its presence nearby with hearing, sight, smell, and other sensations.
Figuring out Illusions
The character has found a strange statue at the end of the hall, though they could’ve sworn they saw some kobolds run down this hallway ahead of them.
Our character now must Investigate the statue, trying to ponder out if it is a secret door. In fact, thanks to their deductive reasoning, they realize that it is simply an illusory duplicate since it doesn’t respond in the right way when they poke and prod it. They can then use their logical mind to see past the illusion and find a door hidden behind it. They can now give chase to the kobolds once again.
Investigation vs Perception
I hope that you now have a greater appreciation of when to call for Investigation vs Perception, and why there are two different skills. Investigation is all about logic and figuring out how complex things work, while Perception is for noticing the world around you and knowing when your sensations aren’t quite what they should be.
Do you have odd examples of Investigation vs Perception? I’d love to hear about it in the comments below!
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