Not once in the story, does Don Norman or any of the people involved recognize a key fact they ALREADY know, even if they don't know they know it:

By intuition, you'll first try to PUSH on a door with a HORIZONTAL bar or handle (or push-plate, of course), and PULL on a door with a VERTICAL handle. This is why the "shit door" at Vox's office is so frustrating - it's a long vertical handle that you have to push! If you have to put a sign on it, like Vox did, the design was screwed up in the first place.