The skin conductance response, also known as the electrodermal response (and in older terminology as "galvanic skin response"), is the phenomenon that the skin momentarily becomes a better conductor of electricity when either external or internal stimuli occur that are physiologically arousing. 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.

The stimuli to which skin conductance is sensitive are manifold, including events of a novel, significant, or intense nature. Arousal level tends to below when a person is sleeping, and high in activated states such as rage or mental workload. When you engage in a mental workload task, such as solving a bunch of math problems (even if not particularly hard), the level willtend to shoot up and then gradually decline. Because many different kinds of events can elevate your skin conductance (strong emotion, a startling event, a demanding task, etc.) it is impossible for an outsider to tell what made your galvactivator glow unless you participate in a highly controlled experiment.

Most people cannot mentally control their skin conductance response in any kind of rapid and fine-tuned way. The response can take seconds to arise and longer to decay. However, you can experiment with thinking of exciting or calming thoughts and watch how your galvactivator responds. Once you have dialed it to your proper baseline, the galvactivator should be sensitive enough to respond to internally-generated imagery in a broad way.

There are only a couple of places where it is widely recognized as easy and reliable to measure the skin conductance response: the palms and the soles of the feet. In these places there is a high density of the eccrine sweat glands, which are known to be responsive to emotional and other psychological stimuli. In either of these areas, the conductance is measured by placing two electrodes next to the skin and passing a tiny electric charge between the two points. When the subject increases in arousal, his/her skin immediately becomes a slightly better conductor of electricity. This response can then be measured and communicated.

The skin conductance response is measured from the eccrine glands, which cover most of the body and are especially dense in the palms and soles ofthe feet. (These are different from the apocrine sweat glands found primarily in the armpits and genital areas.) The primary function of eccrine glands is thermoregulation -- evaporative cooling of the body -- which tends to increase in aerobic activity, so yes, activity can affect conductance.However, the eccrine glands located on the palms and soles have been found to be highly sensitive to emotional and other significant stimuli, with a measurable response that precedes the appearance of sweat.

No. However, when the body is significantly overheated and there is a lot of perspiration, the overall level of skin conductance will indeed climb. You can reset your baseline when this happens if you wish. However, skin conductance is not simply temperature-based. You can also have high conductance when your hands are cold (as when you are nervous) and you can have low conductance when your hands are warm (as when very relaxed). The galvactivator is not merely a temperature sensor like the so-called "mood ring."

Experimental evidence suggests that certain groups of individuals have signature patterns of electrodermal baseline activity. Everyone has an individual baseline, but some people tend to have skin conductance signals that vary relatively little when they are at rest and not being stimulated by either external events or internal thoughts. This category of individuals is often referred to as stabiles. Alternatively, some people have lots of skin conductance responses, even when at rest and when not in the presence of external stimuli; individuals with this pattern are referred to as labiles. Initial attempts to correlate these two physiological predispositions with personality style have been encouraging.

There are a couple of possible reasons why your galvactivator may not be glowing. Here's a list of things to check:

Bad Contact: Are the electrodes on the underside of the glove making good contact with your hand? Make sure the glove is on properly: place it on the left hand, index finger through the little hole, thumb through the big hole,the SENS*BLES star on the back of your hand. Adjust it so that the electrodes are flat against your skin. Turn the dial counterclockwise until it stops so the light will be as bright as possible.

Dry electrodes: In scientific experiments it is customary to use a gel between the skin and electrode. We have found that using electrode gel is not usually necessary with the galvactivator. Nonetheless, for many people it helps to put a small drop of water or saline on the electrodes to improve contact.

Low Baseline: Some people will naturally have very low baselines. We have tried to account for the largest range of baselines in a one-size-fits-all device, but yours may be on the lower end. Try taking a deep breath and holding it for three seconds; this often raises the SC response to a level visible with our device. Blowing up a balloon to popping should bring your level near its maximum.

If you have attempted to address the above suggestions and your galvactivator is still not working, it may have a loose wire or other problem. In this case, feel free to bring it to the galvactivator booth, or to a media lab student.

If your galvactivator tends to always glow very brightly, it may just mean your skin is very conductive! Try turning the dial all the way until the light completely goes off, then dial it back on very slowly, just until you can barely see a hint of light.

No. The amount of conductance in your galvactivator is not enough to hurt anyone. However, we do suggest that anyone wearing a pacemaker not place the heart in the middle of the circuit. This can be avoided by taking care not to have the electrodes touching separate hands. The galvactivator runs from a 6V battery, and the average skin resistance is .1-.4 megaohms. The average current is 10-60 microamps.

The startle reflex is a characteristic spike in the electrodermal response that usually occurs 1-3 seconds after the onset of a startleprobe or a novel stimulus. Typically, a startle probe refers to a loudnoise, bright light, or puff of air designed to “startle” or suddenly divert the attention of the subject. A similar spike in conductance can be generated when a subject "orients" to a new stimulus -- a person suddenly standing next to you, for example.

Habituation is the phenomenon that occurs when several startle probes areprovided in quick succession. The body tends to react strongly to the first one, and will continue to respond, though with less intensity, to subsequent probes. After a certain amount of stimuli, however (which varies fromsubject to subject), the body will stop responding to the startle probes, and the characteristic rise in GSR will cease to occur. However, if the subject is allowed to recover for a while, the startle reflex will become reactivated. The habituation response has been noted to have a very different characteristic in certain categories of schizophrenics.

Not with the galvactivator, though the electrodermal response is one of the measures commonly used as part of a lie detecting apparatus. However, detection of deception requires a thorough experimental setting which does not compare to everyday’s use of the galvactivator.

If an individual causes any kind of significant or intense reaction in you, either good or bad, it can cause your galvactivator to glow. Some people's lights may glow when they think about or see someone who is especially attractive, famous, or important. (But, not glowing does not imply that they do not find you to be any of these!) The galvanic skin response is triggered by many different kinds of events. Simply holding your breath or thinking about something embarrassing or exciting can make it glow. If yours is glowing, you are in the best position to know why, and others can only speculate. Scientific experiments that use skin conductance have to control a situation very carefully, and even then, they cannot control for a person's thoughts.

Everyone's electrodermal response is different. Some may be highly variable in response, while someone else may generate such a slow response that it is hard to visualize. These individual differences simply mean that you can't really compare yourself to your neighbor. The best way to think about the galvactivator is to view it as a device that illuminates your own characteristic response. As you experience different situations, watch for what things consistently make yours glow.

Nobody knows exactly when it was discovered, but the empirical study of electrical changes in human skin was described more than 100 years ago by Vigouroux and by Fere.