The skin is a surprisingly versatile organ. Not only is it smooth and often beautiful to look at, but it also helps regulate many of the body's functions. It acts as a barrier against environmental hazards; it contains nerve cells that detect changes such as temperature and pressure; it can heal itself and (ideally) keeps the body at a constant temperature of 35.6 degrees. Furthermore, the skin responds to changes, or stimuli, in a way that can be accurately measured through the skin's galvanic response, revealing an incredible amount of information about an individual.
Your skin, and much of the rest of your body, conducts electricity. If your body did not conduct electricity, touching a high-voltage fence or sticking a knife into an electrical socket would have no effect on you. We would not be alive without electricity because the body's functions are controlled by electrical signals. The skin in particular is a good conductor of electricity, so even a weak electrical signal introduced to the skin can be measured. By applying a constant, unperceived voltage level to the skin, we can obtain a basic reading of the skin's conductance. The basic reading of skin conductance is called tonic conductance. This level of conductance is different for everyone, but usually ranges from 10 to 50 very small units of conductance called micro-siemens. Tonic skin conductance levels also vary depending on a person's psychological state and self regulation at the time of measurement. While tonic skin conductance is a basic measurement, phasic changes in conductance are a result of the body's response to external stimuli. This increase in conductance from baseline can be observed shortly after the introduction of a subtle stimulus such as an odour, sound, image or question. Phasic changes can be observed when the sweat ducts of the skin fill up in response to a stimulus. After the sweat is deposited or absorbed by the skin, the conductance returns to tonic levels. According to the widely accepted Edelberg sweat circuit model, the magnitude of this increase can be measured by the amount of sweat and the number of activated sweat glands.
Now that you know more about what the galvanic skin response is and how it can be measured, you may wonder why these measurements are important?
To answer this question, let's take a closer look at our autonomic nervous system.
The autonomic nervous system regulates a wide range of body functions, including:
- Heart rate
- Respiratory rate
- Waste elimination
- Fight or flight response
- Blood pressure
- Electrolyte balance
- Sexual response
- Body temperature
The body largely manages these and other functions automatically. The autonomic nervous system is further divided into the parasympathetic and sympathetic nervous systems.
The parasympathetic nervous system regulates the processes of 'rest and digestion' and 'feeding and reproduction', while the sympathetic system regulates functions such as blood pressure, heart rate and the galvanic skin response.
By measuring the galvanic skin response (as well as other sympathetic responses), we can detect emotional arousal and even the level of excitement. This is significant because it is information taken directly from the body. Therefore, readings are an objective look at how we react to a given stimulus.
Because our thoughts are filtered by our conscious mind, what we think may be happening in our body may not be accurate, and we may not be able to see the full picture. With the galvanic skin response, we can bypass the filters of our conscious mind and find out what the body is really trying to tell us with a high degree of accuracy.
Perhaps the best known use of the galvanic skin response is the lie detector, which uses the galvanic skin response to find out how the body is really responding without our conscious filters getting in the way. The galvanic skin response is such a valuable way of observing how the body reacts to certain stimuli that it has been used in a wide variety of fields, including psychological research, psychotherapy but also by the media and for advertising tests, consumer neuroscience and health care.