turning. Or the water turns on and then stops, so we wave our hands up and down, hoping to find the precise location where the water turns on. When I wave my hand in front of the towel dispenser but get no towel, I do not know whether this means the dispenser is broken or out of towels; or that I did the waving wrong, or in the wrong place; or that maybe this doesn’t work by gesture, but I must push, pull, or turn something. The lack of signifiers is a real drawback. These devices aren’t perfect, but at least they got the mapping right.
