The laundry room at my place has a motion-sensor light. If I sit perfectly still for about one minute, the light will turn off. I conducted an experiment to see exactly how much movement it would take to get the light to turn back on. Here are the results: any amount of facial movement without the movement of the head, regardless of how quick or how dramatic the expression, will not turn the light on. The crossing of the legs, however, will turn the light on.