The doors to the SUB

The north portal to the Langara student union building (that is, the exit facing the library) has double doors, with friendly green frames, of the sort where one of the doors extends a sort of metal lip over the gap between them so that they have to be opened the one before the other. They have the curious property that everybody who tries to open them tries the wrong door first. It apparently doesn't matter that there's a sign, in bold, helpful, red-on-white letters, saying "OPEN THIS DOOR FIRST"; others who I see approaching the doors are consistently misled and balked, and I myself, who have been here more than two years, will, unless I'm keeping the problem firmly foremost in my mind, reach quite confidently and unthinkingly for the subordinate door.

I can think of a few explanations for this -- it could be because we're most of us right-handed, for instance (although it doesn't seem to matter which side of the doors we're on), or that there's a general standard for which door has the lip which these doors flout, and our subconscious has noticed that even if we haven't -- but I prefer, because this is what it feels like, to think that it's the side-effect of some nearby perception-altering magic. Something in that part of the SUB, or just outside of it, is out of the ordinary, and ought to draw attention, or at least we ought to wonder sometimes; so those who don't want it to occur to anyone to wonder have put up this spell, or equivalent sufficiently advanced technology, so that we automatically take whatever it is to be so commonplace and unremarkable that our perception of it doesn't even reach our conscious mind. And then, having adjusted ourselves quite unconsciously in response -- perhaps even stepped around it -- we walk into the door.