Wow - a name for it. Thanks!

To digress a bit, when I was working in my former job in public health in the military, "sick building syndrome" was becoming a big deal. (My opinion is that anything called a "syndrome" is something with a bunch of loosely linked symptoms for which no cause, or many causes are identified.) One study I remember reading about was one involving flourescent lights causing headaches and eye strain. These lights actually flash on and off at 440 cycles per second (I think that means 880 "on" flashes per second - please correct me.) It has long been believed that the human eye and brain can't perceive this flashing. The study proposed the theory that people who got headaches around flourescent lights did in fact register the flashing at some sub-perceptable level. There was a double-blind study, where the lights in rooms where individuals worked were replaced by flourescent lights that worked at a higher frequency. The results: people who had the faster-flashing lights had a significant reduction in their symptoms.