Skin conductance is a method of measuring the electrical conductance of the skin. The conductance varies depending on the amount of sweat-induced moisture on the skin. Sweat is controlled by the sympathetic nervous system, so skin conductance is used as an indication of psychological or physiological ”arousal”, due to internal or external stimuli.
Arousal is a broad term referring to overall activation, and is widely considered to be one of the two main dimensions of an emotional response. Measuring arousal is therefore not the same as measuring emotion, but is an important component of it. Arousal has been found to be a strong predictor of attention and memory.
If the sympathetic branch of the autonomic nervous system is highly aroused, then sweat gland activity also increases, which in turn increases skin conductance. In this way, skin conductance can be used as a measure of emotional and sympathetic responses. There has been a long history of electro-dermal activity research, most of it dealing with spontaneous fluctuations or reactions to stimuli.