Chapter 1 endnote 20, from Lisa Feldman Barrett.
Some context is:
They hooked up test subjects to machines to measure changes in the autonomic nervous system: variations in heart rate, temperature, and skin conductance (a measure of sweat).
Scientists can approximate the activity in your sympathetic nervous system by measuring how well your skin conducts electricity. When the activation in your sympathetic nervous system increases, the eccrine sweat glands in your skin fill with sweat. The more you perspire, the more your glands fill, and the better your skin is at conducting electrical activity (because sweat is a weak electrolyte). This measure of electrical activity is called skin conductance or “galvanic skin response.”