This post is going to be a short one, because I am just going to discuss one issue which seems to cause a great deal of grief among players of Dungeons and Dragons 5th edition. There is a lot of confusion about passive Wisdom (Perception) and how it relates to actively rolling Wisdom (Perception). I was confused myself about it long ago, which is why I looked it up. I discovered that nearly everyone else was also at least a little confused about it. Hence why I’m writing about it now. When I was searching for information about it, I discovered that the information was spread around the internet. I got some information from one source, and other information from another source. Now I’m putting all of it together into something which is hopefully easy to understand. I am also adding a bit of my own interpretation into it, explaining how I work it in my campaigns. Feel free to ignore the part at the end with my interpretation as it’s not RAW (rules as written) by any means.
Basically, the problem is this: it shouldn’t be easier to spot things when you aren’t paying attention than when you are actively looking for things. Passive Wisdom (Perception) is equivalent to your character rolling a 10 on a Wisdom (Perception) check. This means that nearly half of the time (whenever you roll 1-9), your active Wisdom (Perception) check score will be worse than it is when you are just tootling along, paying no mind to anything around you. That obviously doesn’t seem right. And it doesn’t seem right because it’s not right.
So what is supposed to be going on?
The short answer to what is happening here is that your passive Wisdom (Perception) score is the lowest score that you can possibly get- it’s what you notice when you’re not paying attention at all. If your passive Wisdom (Perception) didn’t notice something, an active check can be made to try to find it, but if the DC of the hidden thing is below your passive Wisdom (Perception) score, then you already saw it with your passive Wisdom (Perception). This has been verified here by one of the designers of Dungeons and Dragons 5th edition, Mike Mearls, here by D&D designer Dan Dillon, and also here and here by Jeremy Crawford, principles rules designer and lead designer of the Player’s Handbook for D&D 5E, or stated most clearly by him here in a podcast at the 22:14 mark. One of Jeremy Crawford’s Twitter comments is a bit confusing, but he is basically saying that using passive Wisdom (Perception) at all is up to the DM, but if your DM does use passive Wisdom (Perception), your passive Wisdom (Perception) score is the absolute lowest which your Wisdom (Perception) can go. Listen to the podcast if you are at all confused though, as he states very clearly there that your passive Wisdom (Perception) is the floor for your Wisdom (Perception). This interpretation also makes the Observant feat make more sense. The Observant feat (Player’s Handbook p.168) states that “You have a +5 bonus to your passive Wisdom (Perception) and passive Intelligence (Investigation) scores.” If your passive Wisdom (Perception) score wasn’t the floor, that would mean that after taking this feat, 3/4 of the time when actively searching you would not notice things which you easily notice while paying no attention at all. The Observant feat doesn’t raise your maximum Wisdom (Perception) at all, but it raises the minimum significantly.
Beware: My interpretation starts here
Mind you, in my mind there are some situations where passive Wisdom (Perception) won’t help you, and you’ll need to actively roll a Wisdom (Perception) check, but when that happens, your active Wisdom (Perception) roll still will not be below your passive Wisdom (Perception) value. There are times when your passive Wisdom (Perception) will notice something– these examples are given by Dan Dillon. There are also times when your passive Wisdom (Perception) won’t notice something. Walking into a room, you won’t notice an envelope of money taped to the underside of a bed- you would be incapable of seeing that without dropping to the ground and searching under the bed. An orc hiding under the bed, on the other hand, would potentially leave some clues to its presence, like shadows, bits poking out, their smell, or noises they are making. Likewise, a ruby under the pillow wouldn’t be noticed just by walking into the room. In these cases however, if you rolled a Wisdom (Perception) check to search the room, your passive Wisdom (Perception) would again be the lowest which you could roll. I personally tend to allow players to find any humanoids hiding if their passive Wisdom (Perception) is high enough, but any small things which are entirely concealed and would not be producing smells/sounds/movements would need an active Wisdom (Perception) roll. Similarly, if the PC’s are walking past a dead body, they will see their obvious weapons and anything worn on the outside of their clothes, but if they want to loot the body for things in their pockets or hidden away under their clothes they need to roll for that (although the DC will be quite low unless something is hidden well). And speaking of which, passive Intelligence (Investigation) should work pretty much the same way as passive Wisdom (Perception). Those are the only two skills which work this way (unless you’re a rogue with Reliable Talent, in which case all skills work this way) but they both make sense. And yes, I know that there is a lot of confusion about when to use Intelligence (Investigation) versus Wisdom (Perception); I will likely delve into that a bit on another post, but I’m not touching that topic with a ten foot pole right now.
Hopefully that makes passive Wisdom (Perception) less confusing for you. It can certainly be a headache until you understand how it is meant to work.