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How does passive insight/perception skills work? I've read about it and asked people but I keep getting different answers. Any help?

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marked as duplicate by Jonathan Hobbs, SevenSidedDie, LitheOhm, Phil, Oblivious Sage May 2 '13 at 15:31

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Do you have the Rules compendium and access to DDI? –  Brian Ballsun-Stanton May 2 '13 at 5:33
    
    
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1 Answer 1

Note: I'm going to just talk about perception here. Insight works exactly the same way, except that NPCs will roll bluff to try to trick the PCs, rather than stealth to sneak up on / past them.

To calculate a player's passive perception, first calculate their perception modifier: half their level (rounded down) plus their wisdom modifier plus 5 (if they're trained) plus any bonuses from their race/theme/background/items. You should get a number somewhere between -1 and +35. The player's perception rating is 10 plus this number you just calculated.

Now when something is trying to sneak up on the player, it rolls stealth. If it rolls higher than the player's passive perception, then it successfully hid from the player. If it rolls less than or equal to the player's passive perception, the player notices it.

Note that Q&A subforum of the official D&D forums has a stickied thread explaining everything you ever wanted to know about stealth in 4e.

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Hidden Club: Palace 54 of 4e. –  Joshua Aslan Smith May 2 '13 at 14:28
    
Passive Insight and Passive Perception are based on your Insight and Perception skills. D&D thought it would be helpful to calculate Insight and Perception as passive skills because when NPCs are lying or when enemies are trying to sneak up on you, your DM would benefit from knowing the Difficulty Class of sneaking up or of lying to the whole party. Also perception is used to look for loot, traps or other details when roaming around dungeons or... any place really. These passive skills are about how PC perceive their surroundings. –  Eilleen Jun 25 '13 at 21:15
    
In these cases the 'Passive Skills' have a +10 bonus: the +10 'bonus' is actually an average of the roll the game assumes you make. The game assumes then player rolled a d20 and scored a 10. That is the reason of why these 'skill checks' aren't rolled by your players... and from a perspective of D&D being story, this allows more continuity for when a DM is telling you where are you, what do you see, how are the people around you, what are the npcs saying... Hope this helps! –  Eilleen Jun 25 '13 at 21:17
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