Posted on | February 6, 2009 | 2 Comments
What is Galvanic Skin Response (GSR)?
A graph of Galvanic Skin Response (GSR) skin conductance over a 27-minute period during an experiment. Increased GSR indicates a heightened sympathetic nervous system arousal. (Image credit: MIT: Affective Computing).
Galvanic Skin Response is a measure of emotional arousal detected as a sharp increase in electrical skin conductance. It is affected by changes in the salt and water in the sweat gland ducts. So, basically, more you sweat, higher skin conductance. In other words, if you get anxious, embarrassed, angry or something very emotional, there will be a fast increase in the skin’s conductance (i.e. decreases in skin resistance) due to increased activity in the sweat glands (unless the glands are saturated with sweat.)
Since it reacts to anxiety + emotional arousal, the galvanic skin response is traditionally used for a lie detector.
How it works:
GSR is measured by skin’s conductance between two electrodes. Electrodes are small metal plates that apply a very small electrical current (not gonna fry you up ☺) is passed through the skin between electrodes. The electrodes are typically attached to fingers or toes using electrode cuffs (as shown in the picture below) or to any part of the body.
The best materials for the electrode surfaces are non-reactive with the skin:
source: Sean Montgomery
- gold-plated copper
- nickel-plated metal
- silver-silver chloride
- etc…any metal, even two pennies work
*Note that physically moving the electrodes can create spurious changes in the resistance measured across the plates and contaminate the measurement.
Depending on gender, diet, skin type and situation, everyone has different baseline skin conductance. In fact, I had bunch of people whose skins didn’t work well with sensors too.