It never fails, your players are walking through town or hurriedly scanning through papers on a desk looking for something and you think, Shoot, is this a perception or an investigation check??
Some might not think it matters, but you better believe a player with proficiency in investigation and a -1 modifier in perception is going to care which one you pick!
The simple answer is this:
Perception is the player’s ability to spot and detect people or items, it has nothing to do with making intelligent decisions about those people or items.
Investigation is the player’s ability to put together clues and making deductions the others wouldn’t make.
But how exactly does this play out in your campaign? What about situations that fall somewhere in-between?
The Purpose of Perception
The essential purpose of perception is to allow the player to detect the presence or location of something. Perception is a skill that focuses on hearing, spotting or detecting.
This skill does not require intelligence, it requires awareness. This is why a player can have a very high perception, but a very low intelligence score and, thus, a low investigation modifier.
Some examples of good use of perception checks would be:
- Looking for dangerous animals while walking through the woods
- Listening for whispers in a dungeon
- Trying to find a location in a city
- Attempting to spot a hidden enemy
- Catching a scent on the breeze
- Listening for moving water
- Spotting a specific herb or plant
- Searching for a specific item, such as a hidden door or a key
- Finding a hidden person or item
As you can see, most actions players want to accomplish will likely fall into the preception category. These actions all require very little intelligence to complete. Anyone can look for a key in a room or spot a lion in a jungle, as long as they are aware of their surroundings.
Awareness is a special skill on its own. It requires awareness to know your position in a city (a skill I personally do not have!). Players with proficiency in perception are constantly scanning the room and looking out of the corner of their eyes.
These players are aware of what is going on around them at all times, even if they don’t really put two-and-two together about what they see.
Sure, they might notice that the female bartender keeps looking toward the room behind the bar and that the male at table 3 has been gone for a while, but they won’t realize he is stealing from the safe while the bartender (his girlfriend) distracts the owner. That requires a different kind of skill.
To determine if players should roll a perception check ask yourself:
- Are they attempting to hear, spot, or detect something?
- Does this action rely on the awareness of the surroundings?
- Are they attempting to merely perceive or find something, not determine a deeper, hidden message?
If the answer to these questions is “yes” then have the player roll a perception check.
Passive Perception vs Perception Checks
While a perception check is “active,” meaning, the players are asking you to do so something, there is another kind of perception.
Passive perception can be found at the bottom of the skills list on a player’s character sheet. (This number is 10 plus the player’s wisdom modifier)
Honestly, most DMs forget all about passive perception. I am as guilty as anyone, but it is a very useful mechanic. Passive perception is the level of awareness the player displays in general.
While walking through town, the woods, or sitting in a bar, passive perception lets the DM know how much each player would notice naturally. I like to use this mechanic to determine who would notice an NPC, an event, or unique items without prompting.
Great use of passive perception is to describe a room or situation in general, then tell the players with the highest passive perception, “In addition, you notice…” and give more revealing details to just those players with high passive perception.
The Purpose of Investigation
Unlike perception, the purpose of investigation is to make deductions and follow clues. While perception is awareness of the surrounding world, investigation seeks to discover the hidden message or ideas.
Investigation requires intelligence. Smart players will not simply search an entire room for a key, they will try to deduce where the person might place/hide the key based on what they know about them. This is a completely different skill.
Ask for an investigation check when players:
- Try to piece together clues to discover something hidden
- Attempt to understand what images, carvings, or items mean
- Attempt to pinpoint locations of items based on what they know about the NPC
- Look at tracks, scratches, or moved items and attempt to understand what that means about the creature or situation
As you can see, investigation goes far beyond the simple scouring of an area. It seeks to understand the details and meaning behind what is found. A great combination is a highly perceptive player who finds clues then turns them over to the investigative player who understands what they mean.
Just because you can find a clue, doesn’t mean you can understand it, that’s where investigation comes in. If players are just trying to find something, then it is NOT investigation, no matter how long they take to search for it.
Biggest Mistakes DMs Make
Often, DMs think that the difference between perception and investigation is simply how long the player wants to take to search. But this is NOT the case.
These are completely different skills for different types of players.
You can tell the difference based on how the player askes. If the player simply askes to search the room for something, ask for perception. On the other hand, if they are asking if they can tell why something is there, it is investigation.
Examples of Differences Between Perception and Investigation
To help you better determine if you should ask for a perception or an investigation check, I made this chart. You will see examples of what a player might say or ask sorted into either Perception or Investigation.
Perception Awareness | Investigation Intelligence |
| Can I search the room for a hidden door? | I want to look at the bookcase and try to determine if any of the books are fake and might be levers to open a door. |
| I want to search the office for any papers or documents | Looking at the documents, can I tell who might be the secret contact or if they are involved in illegal activity? |
| I look around the bar, do I notice anything strange? | Can I determine why the NPC is so upset? |
| As we are walking, I want to look out for a magical items shop | I want to look at the building, can I tell how old it is or what kind of clientele they serve? |
| I want to look for tracks | Can I tell how heavy the animal is based on its tracks? |
| Is there anything amiss in the room? | Can I tell if these are scratch marks from the door or from something else? |
If in doubt, simple ask, “Is this a basic task, or would this require intelligence and training?” If you follow this simple rule, you will likely make the right call, most of the time.
But remember, we all make mistakes. If you do botch a ruling, it can disrupt the flow of the game and make players upset. However, there is a correct way to deal with those situations that keep the game rolling, feel free to see my article on What to Do If You Miss a Call for tips on that.
Until next time,
May your game have advantage, my friends!
-Halfling Hannah
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