from what i've heard, the frequency at which our brain interprets the image coming into our eyes is between 60 and 80 hertz. my old software design teacher told me this when i asked him for some help and he said "excuse me" and changed the settings up to 80 hertz and explained that otherwise the image was constantly flickering, from what he could see. a quick look at wikipedia doesn't seem to confirm this, but that's just what i heard.

julz