Tales of Justice
One of the things that separates Player Characters from average citizens is that a Player Character’s stats are not all 2.
Another thing that separates Player Characters from average citizens is that a Player Character theoretically has an amazing ability to notice some detail of the world around him, and use that information to his advantage!
Except, of course, that our party is really good at rolling whammies when the GM calls for a “Perception Check”. Who, me? I perceive NOTHING! La la la, nothing to see or hear, I wonder if everyone’s caught up on the latest episodes of Supergirl?
If no special conditions apply, a Perception Check (definitely and always a Dice Action) uses the character’s Int/Will versus (a person did not want you to percieve this object or action or other physical-world thing:) the opponent’s Int/Mind, or maybe (a mood or an emotional state:) the opponent’s Infl/Aura. Or, if the information to be percieved is none of the above, the GM has a Universal Modifier Chart that helps determine difficulty for specific clues, obscure events, and so forth.
Technically, most Perception Checks are supposed to be rolled by the GM without PC input, although a PC is always allowed to say, “I want to try a Perception Check here to see if I can spot” fill-in-the-blank, and possibly also spend HP on improving the roll. Sometimes we do roll for you guys without telling you beforehand, but a lot of times we ask you to roll it because that’s more fun for everybody than watching the GM do things behind her GM screen and mutter.
Obviously, relevant Powers and Skills might replace the usual Int/Will stats. Sharp Eye improves your chances. Fog or Darkness might decrease an opponent’s perceptiveness. Any character swept up in a Psychological Instability or Traumatic Flashback probably does not get to roll in the first place.
Since a Perception Check is a Dice Action, if one is made during a combat phase, no other Dice Action can be taken that phase!