I've been trying to figure out whether a character needs to actively be looking for traps (i.e. spending a move action) in order to be able to find them or she simply gets a reactive check when she comes close. I remember that in D&D 3.5, you'd get Spot and Search as skills, and you needed Search to find traps, which was an active looking for. But in Pathfinder both things are conflated in Perception, which can be reactive or active.
The skill description lists the action as "Find a hidden trap," as opposed to "Notice a hidden trap." Does using the verb "find" mean that it must be done through active searching?
Best Answer
Usually, yes - an active search effort is required.
The rules seem to presume that characters do not notice traps unless they are actively looking for them, though some characters may have abilities which change this rule. For instance, the text of the Find Traps spell states:
This implies that if you are not actively searching, you do not get an automatic check to notice a trap. The Rogue Talent Trap Spotter is similar:
And the Dwarven racial feature Stonecunning grants the same thing to all dwarves in relation to unusual stonework:
None of these abilities would be worth much if you could already always make a reactive perception check to spot a trap.
However, a GM might sometimes rule that a trap is obvious enough that anyone can make a reactive perception check to spot it; some traps just are not particularly hidden. You could imagine, for instance, a swinging spiked log that is just attached to the ceiling of a corridor; the characters might not notice it, because it's dark and they'd have to look up to the ceiling, but it is not really so hidden that it requires active searching effort to be able to spot.