Man, it is known, is the only mammal that knows how to blush. A study has not been made with regards the connection between skin resistance and tension. One thing is certain,though tension affects sweat glands which in turn affects some change in the membrane permeability of the skin. This change in permeability is the major cause of alternations in electrical activity. The main idea is, when tension increases, skin resistance falls,when tension decreases,skin resistance rises. Credit should be given to a scientist of the 19th century M.Ch.fere, who discovered that the resistances of the skin is compared to a small electric current change in response to aroused emotions. Based on this discovery, the polygraph, or lie detector, was invented. It responded to the tension generated when a person is lying.