I very much agree with Maitrecorbo on how to do a 'perception' check. In the 2 games I've run, I told my players that a roll is a certain arena (or approach, it depends on the story, but mental is the go to for investigations/noticing things) and given them usually a choice of 2 skills to roll with it, but a few times I've had a player spin a good enough reason to use a different skill and I have let them do it.