Perception

Description

Ability Score Used:	Wisdom
Usable Untrained?	Yes
Armor Check Penalty Applies?	No

Your senses allow you to notice fine details and alert you to danger. Perception is the skill of using those senses to their maximum effect, keenly finding the minute details that others miss. Perception covers all five senses, including sight, hearing, touch, taste, and smell.

Passive Perception

All creatures have a passive perception, which is equal to their perception skill's total bonus plus 10. Passive perception is always on (unless you are unconscious or your senses are somehow impaired), and is a free action to use. This is the equivalent of taking 10, except that it can be used at any time, even during combat.

Passive perception has a number of drawbacks, due to the fact that you're not really looking around terribly hard, or truly prepared for surprises or danger. Invisible creatures, for example, cannot be detected with passive perception checks at all.

Perception can also be used actively, representing your character taking a moment to really look around, search for particular things, or generally be hyper-aware of their surroundings.

Spot

Perception is most commonly used to oppose an opponent's Stealth, to notice the opponent and avoid being surprised. If you are successful, you notice the opponent and can react accordingly. If you fail, your opponent can take a variety of actions, including sneaking past you or attacking you. Perception is also used to notice fine details in the environment. The DC to notice such details varies depending upon distance, the environment, and how noticeable the detail is. As a note, finding a trap requires you to be adjacent to the square you are checking for traps unless there are feats, abilities, magic items, etc which modify that task. Noticing large, obvious details (such as creatures size Small or larger) only takes a -1 per ten feet if there are poor visibility conditions. In clear conditions such rolls are typically -1 per one hundred feet, and if creatures are larger than size medium, the distance for each minus 1 is multiplied by each size category larger than size small. Thus, size medium is -1 per 100 feet, large is -1 per 200 feet, huge is -1 per three hundred feet, etc.
Action Required:	Most Perception checks are reactive, made in response to observable stimulus. These are 'passive' perception checks and are free actions, although it is unusual for more than one Perception check to be allowed at once. Intentionally searching for stimulus is an 'active' perception check, and involves all opposed rolls as well as 'general' perception checks. Such active perception checks are a move action. You may make more than one per round in battle if you wish to spend the actions, but in general, you may only notice one thing at a time with an active check.
DC of Check:	The DC of the check (noted in the table) is either based upon the stimulus you are impinged with, the environment you are within, or the abilities of an opponent. Detail Perception DC Hear the sound of battle -10 Notice the stench of rotting garbage -10 Detect the smell of smoke 0 Hear the details of a conversation 0 Notice a visible creature 0 Determine if food is spoiled 5 Hear the sound of a creature walking 10 Hear the details of a whispered conversation 15 Find the average concealed door 15 Hear the sound of a key being turned in a lock 20 Find the average secret door 20 Hear a bow being drawn 25 Sense a burrowing creature underneath you 25 General 'perception check' to gain useful information about a scene, room, or area Average DC for the CL of the area or the Campaign level Notice a pickpocket Opposed by Sleight of Hand Notice a Disguised creature Opposed by Disguise Notice a Camouflaged object or motionless creatures Opposed by Disguise Notice a creature using Stealth Opposed by Stealth Find a hidden trap Varies by trap Identify the powers of a potion through taste 10 + 2 x the potion's caster level
Modifiers to Check	Perception Modifiers DC Modifier Distance to the source, object, or creature +1/10 feet Distance in hazy, dusty, heat-distorted, shimmery, on other Planes, etc +1/5 feet Through a closed door +5 Through a wall +10/foot of thickness Favorable conditions1 -2 Unfavorable conditions1 +2 Terrible conditions2 +5 Making an active Perception check as a swift action +5 Creature making the check is distracted +5 Creature making the check is asleep +10 Creature or object is invisible to sense making check +4 (Epic Only) Pierce Obscurement +10 per square of fog, smoke, cloud, etc. (Epic Only) Sense Magic +50 to sense the presence of an active magical effect (Epic only) Notice inanimate, unmoving, invisible object +40 to check to determine something is in the room (Epic Only) Pinpoint inanimate, unmoving, invisible object +50 to determine which square such an item is in, although miss chance may apply 1 Favorable and unfavorable conditions depend upon the sense being used to make the check. For example, bright light might decrease the DC of checks involving sight, while torchlight or moonlight might give a penalty. Background noise might increase a DC involving hearing, while competing odors might penalize any DC involving scent. 2 As for unfavorable conditions, but more extreme. For example, candlelight for DCs involving sight, a roaring dragon for DCs involving hearing, and an overpowering stench covering the area for DCs involving scent.
Take 10? / Take 20?	You can take 10 as long as you are not in combat. You can take 20 as long as the stimulus is present for at least the next 20 rounds.
Allows Assists?	No. Having friends nearby does not help, although if they notice something with a separate roll, they may certainly point it out to you.
Results of Success	You notice the stimulus in question and may take actions based upon it.
Consequences of Failure	You do not notice the stimulus in question and may not take actions based upon it.
Retry Allowed?	Special. If the stimulus is fleeting, then if you miss it, it is gone. If the stimulus is ongoing (a faint humming in the air, for example) you may retry up to once per round you are exposed to the stimulus.
Provokes AOO?	No.