Skin conductance is not under conscious control. Instead, it is modulated autonomously by sympathetic<unk>  which drives human behavior, cognitive and emotional states on a subconscious level. Skin conductance, therefore, offers direct insights into autonomous emotional regulation. Human extremities, including fingers, palms, and soles of feet display different bio-electrical phenomena. They can be detected with an<unk>  meter, a device that displays the change electrical conductance between two points over time. The two current paths are along the surface of the skin and through the body. Active measuring involves sending a small amount of current through the body. Some studies include the human skin's response to alternating current, including recently deceased bodies. Physiological basis There is a relationship between emotional arousal and sympathetic<unk> , although the electrical change alone does not identify which specific emotion is being elicited. These autonomic sympathetic changes alter sweat and blood flow, which in turn affects GSR and GSP. The amount of sweat glands varies across the human body, being highest in hand and foot regions (200–600 sweat glands per cm2). The response of the skin and muscle tissue to external and internal stimuli can cause the conductance to vary by several microsiemens. A correctly calibrated device can record and display the subtle changes. The combined changes between<unk>  resistance and<unk>  potential make up<unk> . Galvanic skin resistance (GSR) is an older term that refers to the recorded electrical resistance between two electrodes when a very weak current is steadily passed between them. The electrodes are normally placed about an inch apart, and the resistance recorded varies according to the emotional state of the subject. Galvanic skin potential (GSP) refers to the voltage measured between two electrodes without any externally applied current. It is measured by connecting the electrodes to a voltage amplifier. This voltage also varies with the emotional state of the subject. Examples A painful stimulus such as a pinprick elicits a sympathetic response by the sweat glands, increasing secretion. Although this increase is generally very small, sweat contains water and electrolytes, which increase electrical conductivity, thus lowering the electrical resistance of the skin. These changes in turn affect GSR. Another common manifestation is the vasodilation (dilation) of blood vessels in the face, referred to as blushing, as well as increased sweating that occurs when one is embarrassed.<unk>  is highly responsive to emotions in some people. Fear, anger, startled response, orienting response, and sexual feelings are among the reactions that may be reflected in<unk> . These responses are utilized as part of the polygraph or lie detector test.<unk>  in regular subjects differs according to feelings of being treated fairly or unfairly, but psychopaths have been shown to manifest no such differences. This indicates that the<unk>  record of a polygraph may be deceptive in a criminal investigation. Different units of<unk> <unk>  reflects both slow varying tonic sympathetic<unk>  and fast varying phasic sympathetic<unk> . Tonic<unk>  can be expressed in units of<unk>  level (SCL), while phasic<unk>  is expressed in units of<unk>  responses (EDR). Phasic changes (EDR) are short-lasting changes in<unk>  that appear as a response to a distinct stimulus. EDRs can also appear spontaneously without an observable external stimulus. These types of EDRs are referred to as “nonspecific EDR” (NS.EDR). The phasic SCR is useful when investigating multifaceted attentional processes. Tonic changes (EDL) are based on the phasic parameters. The spontaneous fluctuations of nonspecific EDR can be used to evaluate tonic<unk> . More specifically by using the frequency of “nonspecific EDR” as an index of<unk>  during a specific time period, e. g. 30–60 seconds. Tonic<unk>  is considered useful in investigations of general arousal and alertness.
Electrodermal activity
Basal body temperature
Muscle tone
Heart rate variability
Myogenic tone
Vagal tone
Optokinetic response
Basal metabolic rate