If you submerge one hand in hot water and the other in ice-water simultaneously for about a minute, then immediately put both in room temperature water, what will be the temperature sensation of each hand?
Most of our sensory systems respond to **changes** in stimuli. They are not absolute detectors.
Thus if a stimulus is constant, it will eventually be ignored by the nervous system. Cases in point. Why don’t you feel the clothes you are wearing after you put them on? Because they exert a constant pressure on your skin. Why don’t you hear (after a while) a constant noise (like an overhead projector)? Because it’s a constant sound.
So eventually the hands in the hot and ice water …. their temperature inputs….. will be ignored, until you place both hands in a different temperature. Then the nervous system will detect the CHANGE in the temperature stimulus, and interpret it on the basis of the PREVIOUS input. So the “hot” hand previously will feel cooler, the “ice” hand will feel hotter, even though both are in the same water.