Rub your index fingers gently over a piece of very coarse sandpaper a few times and rate its coarseness on a scale from 1 (very soft) to 7 (very coarse). After a minute or two, rub the same finger over the paper and again rate its coarseness. Did your perception of the coarseness change? How?
Distribute one cup with sugar water and one with fresh water. Take a sip of the sugar water and swish it around in your mouth for several seconds without swallowing it; gradually, it should taste less sweet. After swallowing it (or spitting it back into the cup), taste from the cup containing fresh water. Did the taste of the fresh water surprise you? How?
Take about 15 index cards and a flashlight that is opaque on all sides (so that light shines only through the front) into a very dark room. After placing all 15 cards over the beam of light, slowly remove the cards one at a time until you can barely detect the light, and then count the number of cards that remain over the light. After a few minutes, the light should begin to look brighter. When this is the case, add a card and see if you can still see the light. Repeat this process of gradually adding cards over a 15-minute period. Were you able to detect an increasingly dim light the longer you spent in the dark?
Fill 3 medium-sized bowls with (a) very hot (but not painfully so) tap water, (b) very cold tap water, and (c) a mixture of the very hot and very cold water. Arrange them, so your right hand is in front of the cold water, your left hand is in front of the hot water, and the lukewarm water is in the middle. Submerse your hands into the water (right into cold, left into hot) for about 3 minutes. After 3 minutes, quickly transfer both hands to the lukewarm (middle) bowl. What did you sense?
In all four experiments, you will experience adaptation. What is it? Describe the systems that receive sensory information in these experiments....