pathfinder2e-notes/content/Mechanics/Rules/Perception.md
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# Perception
*Source* Core Rulebook pg. 464 3.0
Your Perception measures your ability to notice things, search for whats [Hidden](../Conditions/Hidden.md), and tell whether something about a situation is suspicious. This statistic is frequently used for rolling initiative to determine who goes first in an encounter, and its also used for the [Seek](Actions/Seek.md) action.
The rules for rolling a Perception check are found on page 448. The rules below describe the effects of light and visibility on your specific senses to perceive the world, as well as the rules for sensing and locating creatures with Perception.
## Light
*Source* Core Rulebook pg. 464 3.0
The amount of light in an area can affect how well you see things. There are three levels of light: bright light, dim light, and [1 TTRPG/PF2e Wiki/Traits/Darkness](1%20TTRPG/PF2e%20Wiki/Traits/Darkness). The rules in this book assume that all creatures are in bright light unless otherwise noted. A source of light lists the radius in which it sheds bright light, and it sheds dim light to double that radius.
### Bright Light
*Source* Core Rulebook pg. 464 3.0
In bright light, such as sunlight, creatures and objects can be [Observed](../Conditions/Observed.md) clearly by anyone with average vision or better. Some types of creatures are [Dazzled](../Conditions/Dazzled.md) or [Blinded](../Conditions/Blinded.md) by bright light.
### Dim Light
*Source* Core Rulebook pg. 464 3.0
Areas in shadow or lit by weak light sources are in dim light. Creatures and objects in dim light have the [Concealed](../Conditions/Concealed.md) condition, unless the seeker has [1 TTRPG/PF2e Wiki/Bestiary/Abilities/Darkvision](1%20TTRPG/PF2e%20Wiki/Bestiary/Abilities/Darkvision) or [Low-Light Vision](../Bestiary/Abilities/Low-Light%20Vision.md) (see Special Senses on page 465), or a precise sense other than vision.
### Darkness
*Source* Core Rulebook pg. 464 3.0
A creature or object within darkness is [Hidden](../Conditions/Hidden.md) or [Undetected](../Conditions/Undetected.md) unless the seeker has [1 TTRPG/PF2e Wiki/Bestiary/Abilities/Darkvision](1%20TTRPG/PF2e%20Wiki/Bestiary/Abilities/Darkvision) or a precise sense other than vision (Special Senses are on page 465). A creature without darkvision or another means of perceiving in darkness has the [Blinded](../Conditions/Blinded.md) condition while in darkness, though it might be able to see illuminated areas beyond the darkness.
If a creature can see into an illuminated area, it can observe creatures within that illuminated area normally. After being in darkness, sudden exposure to bright light might make you [Dazzled](../Conditions/Dazzled.md) for a short time, as determined by the GM.
## Senses
*Source* Core Rulebook pg. 464 3.0
The ways a creature can use Perception depend on what senses it has. The primary concepts you need to know for understanding senses are precise senses, imprecise senses, and the three states of detection a target can be in: observed, hidden, or undetected. Vision, hearing, and scent are three prominent senses, but they dont have the same degree of acuity.
### Precise Senses
*Source* Core Rulebook pg. 464 3.0
Average vision is a precise sense—a sense that can be used to perceive the world in nuanced detail. The only way to target a creature without having drawbacks is to use a precise sense. You can usually detect a creature automatically with a precise sense unless that creature is [hiding](../Conditions/Hidden.md) or obscured by the environment, in which case you can use the [Seek](Actions/Seek.md) basic action to better detect the creature.
### Imprecise Senses
*Source* Core Rulebook pg. 464 3.0
Hearing is an imprecise sense—it cannot detect the full range of detail that a precise sense can. You can usually sense a creature automatically with an imprecise sense, but it has the hidden condition instead of the observed condition. It might be undetected by you if its using Stealth or is in an environment that distorts the sense, such as a noisy room in the case of hearing.
In those cases, you have to use the [Seek](Actions/Seek.md) basic action to detect the creature. At best, an imprecise sense can be used to make an [Undetected](../Conditions/Undetected.md) creature (or one you didnt even know was there) merely [Hidden](../Conditions/Hidden.md)—it cant make the creature [Observed](../Conditions/Observed.md).
### Vague Senses
*Source* Core Rulebook pg. 465 3.0
A character also has many vague senses—ones that can alert you that something is there but arent useful for zeroing in on it to determine exactly what it is. The most useful of these for a typical character is the sense of smell. At best, a vague sense can be used to detect the presence of an [Unnoticed](../Conditions/Unnoticed.md) creature, making it [Undetected](../Conditions/Undetected.md). Even then, the vague sense isnt sufficient to make the creature [Hidden](../Conditions/Hidden.md) or [Observed](../Conditions/Observed.md).
When one creature might detect another, the GM almost always uses the most precise sense available.
Pathfinders rules assume that a given creature has vision as its only precise sense and hearing as its only imprecise sense. Some characters and creatures, however, have precise or imprecise senses that dont match this assumption. For instance, a character with poor vision might treat that sense as imprecise, an animal with the scent ability can use its sense of smell as an imprecise sense, and a creature with echolocation or a similar ability can use hearing as a precise sense. Such senses are often given special names and appear as “echolocation (precise),” “scent (imprecise) 30 feet,” or the like.
### Special Senses
*Source* Core Rulebook pg. 465 3.0
While a human might have a difficult time making creatures out in dim light, an elf can see those creatures just fine. And though elves have no problem seeing on a moonlit night, their vision cannot penetrate complete darkness, whereas a dwarfs can.
Special senses grant greater awareness that allows a creature with these senses to either ignore or reduce the effects of the undetected, hidden, or concealed conditions (described in Detecting Creatures below) when it comes to situations that foil average vision. The following are a few examples of common special senses.
#### Detecting with Other Senses
If a monster uses a sense other than vision, the GM can adapt the variables that keep its foes from being detected to equivalents that work with the monsters senses. For example, a creature that has echolocation might use hearing as a primary sense. This could mean its quarry is concealed in a noisy chamber, hidden in a great enough din, or even [Invisible](../Conditions/Invisible.md) in the area of a silence spell.
##### Using Stealth with Other Senses
The Stealth skill is designed to use Hide for avoiding visual detection and Avoid Notice and Sneak to avoid being both seen and heard. For many special senses, a player can describe how theyre avoiding detection by that special sense and use the most applicable Stealth action. For instance, a creature stepping lightly to avoid being detected via tremorsense would be using Sneak.
In some cases, rolling a Dexterity-based Stealth skill check to Sneak doesnt make the most sense. For example, when facing a creature that can detect heartbeats, a PC trying to avoid being detected might meditate to slow their heart rate, using Wisdom instead of Dexterity as the ability modifier for the Stealth check. When a creature that can detect you has multiple senses, such as if it could also hear or see, the PC would use the lowest applicable ability modifier for the check.
### Darkvision and Greater Darkvision
*Source* Core Rulebook pg. 465 3.0
A creature with darkvision or greater darkvision can see perfectly well in areas of darkness and dim light, though such vision is in black and white only. Some forms of magical darkness, such as a 4th-level darkness spell, block normal darkvision. A creature with greater darkvision, however, can see through even these forms of magical darkness.
### Low-Light Vision
*Source* Core Rulebook pg. 465 3.0
A creature with low-light vision can see in dim light as though it were bright light, so it ignores the concealed condition due to dim light.
### Scent
*Source* Core Rulebook pg. 465 3.0
Scent involves sensing creatures or objects by smell, and is usually a vague sense. The range is listed in the ability, and it functions only if the creature or object being detected emits an aroma (for instance, incorporeal creatures usually do not exude an aroma).
If a creature emits a heavy aroma or is upwind, the GM can double or even triple the range of scent abilities used to detect that creature, and the GM can reduce the range if a creature is downwind.
### Tremorsense
*Source* Core Rulebook pg. 465 3.0
Tremorsense allows a creature to feel the vibrations through a solid surface caused by movement. It is usually an imprecise sense with a limited range (listed in the ability). Tremorsense functions only if the detecting creature is on the same surface as the subject, and only if the subject is moving along (or burrowing through) the surface.
## Detecting Creatures
*Source* Core Rulebook pg. 465 3.0
There are three conditions that measure the degree to which you can sense a creature: [Observed](../Conditions/Observed.md), [Hidden](../Conditions/Hidden.md), and [Undetected](../Conditions/Undetected.md). However, the [Concealed](../Conditions/Concealed.md) and [Invisible](../Conditions/Invisible.md) conditions can partially mask a creature, and the [Unnoticed](../Conditions/Unnoticed.md) condition indicates you have no idea a creature is around.
With the exception of invisible, these conditions are relative to the viewer—it's possible for a creature to be observed to you but hidden from your ally. When you're trying to target a creature that's hard to see or otherwise sense, various drawbacks apply. Most of these rules apply to objects you're trying to detect as well as creatures.
Typically, the GM tracks how well creatures detect each other, since neither party has perfect information. For example, you might think a creature is in the last place you sensed it, but it was able to Sneak away. Or you might think a creature can't see you in the dark, but it has darkvision.
You can attempt to avoid detection by using the Stealth skill to [Avoid Notice](../Activities/Avoid%20Notice.md), [Hide](Actions/Hide.md), or Sneak, or by using Deception to Create a Diversion.
### Observed
*Source* Core Rulebook pg. 466 3.0
In most circumstances, you can sense creatures without difficulty and target them normally. Creatures in this state are observed. Observing requires a precise sense, which for most creatures means sight, but see the Detecting with Other Senses sidebar (page 465) for advice regarding creatures that dont use sight as their primary sense. If you cant observe the creature, its either hidden, undetected, or unnoticed, and youll need to factor in the targeting restrictions. Even if a creature is observed, it might still be concealed.
### Hidden
*Source* Core Rulebook pg. 466 3.0
A creature thats hidden is only barely perceptible. You know what space a hidden creature occupies, but little else. Perhaps the creature just moved behind cover and successfully used the Hide action. Your target might be in a deep fogbank or behind a waterfall, where you can see some movement but cant determine an exact location. Maybe youve been blinded or the creature is under the effects of [1 TTRPG/PF2e Wiki/Magic/Spells/Level 2/Invisibility](1%20TTRPG/PF2e%20Wiki/Magic/Spells/Level%202/Invisibility), but you used the [Seek](Actions/Seek.md) basic action to determine its general location based on hearing alone. Regardless of the specifics, youre [Flat-footed](../Conditions/Flat-footed.md) to a hidden creature.
When targeting a hidden creature, before you roll to determine your effect, you must attempt a DC 11 flat check. If you fail, you dont affect the creature, though the actions you used are still expended—as well as any spell slots, costs, and other resources. You remain flat-footed to the creature, whether you successfully target it or not.
### Undetected
*Source* Core Rulebook pg. 466 3.0
If a creature is undetected, you dont know what space it occupies, youre flat-footed to it, and you cant easily target it. Using the Seek basic action can help you find an undetected creature, usually making it hidden from you instead of undetected. If a creature is undetected, that doesnt necessarily mean youre unaware of its presence—you might suspect an undetected creature is in the room with you, even though youre unable to find its space. The unnoticed condition covers creatures youre entirely unaware of.
Targeting an undetected creature is difficult. If you suspect theres a creature around, you can pick a square and attempt an attack. This works like targeting a hidden creature, but the flat check and attack roll are both rolled in secret by the GM. The GM wont tell you why you missed—whether it was due to failing the flat check, rolling an insufficient attack roll, or choosing the wrong square. The GM might allow you to try targeting an undetected creature with some spells or other abilities in a similar fashion. Undetected creatures are subject to area effects normally.
For instance, suppose an enemy elf wizard cast [1 TTRPG/PF2e Wiki/Magic/Spells/Level 2/Invisibility](1%20TTRPG/PF2e%20Wiki/Magic/Spells/Level%202/Invisibility) and then [Sneaked](Actions/Sneak.md) away. You suspect that with the elfs Speed of 30 feet, they probably moved 15 feet toward an open door. You move up and attack a space 15 feet from where the elf started and directly on the path to the door.
The GM secretly rolls an attack roll and flat check, but they know that you were not quite correct—the elf was actually in the adjacent space! The GM tells you that you missed, so you decide to make your next attack on the adjacent space, just in case. This time, its the right space, and the GMs secret attack roll and flat check both succeed, so you hit!
### Unnoticed
*Source* Core Rulebook pg. 467 3.0
If you have no idea a creature is even present, that creature is unnoticed by you. A creature that is undetected might also be unnoticed. This condition usually matters for abilities that can be used only against targets totally unaware of your presence.
## Concealment and Invisibility
*Source* Core Rulebook pg. 467 3.0
The concealed and invisible conditions reflect certain circumstances that can make a creature harder to see.
### Concealed
*Source* Core Rulebook pg. 467 3.0
This condition protects a creature if its in mist, within dim light, or amid something else that obscures sight but does not provide a physical barrier to effects. An effect or type of terrain that describes an area of concealment makes all creatures within it concealed.
When you target a creature thats concealed from you, you must attempt a DC 5 flat check before you roll to determine your effect. If you fail, you dont affect the target. The concealed condition doesnt change which of the main categories of detection apply to the creature. A creature in a light fog bank is still observed even though its concealed.
### Invisible
*Source* Core Rulebook pg. 467 3.0
A creature with the invisible condition (by way of an [1 TTRPG/PF2e Wiki/Magic/Spells/Level 2/Invisibility](1%20TTRPG/PF2e%20Wiki/Magic/Spells/Level%202/Invisibility) spell or invisibility potion, for example) is automatically [Undetected](../Conditions/Undetected.md) to any creatures relying on sight as their only precise sense. Precise senses other than sight ignore the invisible condition.
You can use the Seek basic action to attempt to figure out an invisible creatures location, making it instead only hidden from you. This lasts until the invisible creature successfully uses Sneak to become undetected again. If youre already observing a creature when it becomes invisible, it starts out hidden, since you know where it was when it became invisible, though it can then Sneak to become undetected.
Other effects might make an invisible creature hidden or even observed but concealed. For instance, if you were tracking an invisible creatures footprints through the snow, the footprints would make it hidden. Similarly, throwing a net over an invisible creature would make it observed but concealed for as long as the net is on the creature.