Skin conductance, also known as Galvanic Skin Response (GSR) or electrodermal activity (EDA), measures changes in the skin’s electrical conductivity. This non-invasive method gauges the body’s unconscious reactions by indicating sweat gland activity, which is influenced by emotional states.
The Link Between Emotions and Sweat
Our emotional responses are intimately connected to the body’s automatic functions, particularly through the autonomic nervous system. This system operates largely outside conscious control and is responsible for regulating bodily processes like heart rate, digestion, and sweat production. When faced with emotionally stimulating situations, such as excitement, stress, or fear, a branch of this system called the sympathetic nervous system becomes active.
This activation triggers what is often described as the “fight-or-flight” response, preparing the body for immediate action. A direct result of sympathetic activation is the stimulation of eccrine sweat glands, which are found across most of the body but are particularly concentrated on the palms of the hands and the soles of the feet. These glands primarily produce a watery sweat containing electrolytes like sodium and chloride.
As sweat is secreted onto the skin’s surface, it fills the sweat ducts and spreads across the skin. This moist, electrolyte-rich layer significantly increases the skin’s ability to conduct electricity. Therefore, increased emotional arousal leads to greater sweat production, enhancing the skin’s electrical conductance.
How Skin Conductance Is Measured
Measuring skin conductance involves placing small, non-invasive sensors, or electrodes, directly onto the skin. These electrodes are most commonly positioned on the fingertips or the palm, areas with a high density of eccrine sweat glands. A very low, imperceptible electrical voltage is then applied between these two electrodes. The device subsequently measures the minute changes in the electrical current that flows through the skin.
The measurements taken can be categorized into two primary types. The “tonic level” refers to the relatively slow-changing baseline level of skin conductance when a person is in a relaxed state, without specific external stimuli. This baseline can slowly drift over time, reflecting general arousal levels.
“Phasic responses,” in contrast, are rapid, temporary increases in skin conductance that occur quickly after a specific event or stimulus. For instance, hearing a sudden loud noise or seeing a startling image can elicit a sharp, brief spike in conductance. To illustrate, imagine a calm lake representing the tonic level; when a stone is thrown in, the ripples spreading outwards are akin to a phasic response, a temporary disturbance to the baseline.
Real-World Uses of Skin Conductance Data
Skin conductance data serves as an objective measure across various fields. In psychological research, it is frequently used to quantify the intensity of emotional arousal in studies investigating anxiety disorders, specific phobias, and how individuals regulate their emotions. Researchers can observe physiological responses to different stimuli, offering insights beyond self-reported feelings.
Skin conductance is a component of polygraph testing, often referred to as “lie detector” tests. During these examinations, changes in skin conductance are monitored alongside other physiological signals like heart rate and respiration, under the premise that deceptive answers may elicit a heightened arousal response. However, the scientific community widely debates the overall accuracy and reliability of polygraph tests, noting that arousal can stem from various emotions, not just deception.
In the commercial sector, neuromarketing leverages skin conductance to gauge unconscious emotional reactions to advertisements, product packaging, or user experiences with websites and apps. Companies analyze these physiological responses to understand which elements evoke the strongest emotional engagement, helping refine marketing strategies and product designs with data on genuine, immediate reactions.
The application of skin conductance has also extended into modern wearable technology, such as smartwatches and fitness trackers. These devices can monitor fluctuations in skin conductance throughout the day, providing users with an indication of their stress levels or periods of heightened arousal. This data can be used in biofeedback therapy, where individuals learn to consciously control their physiological responses to manage stress or anxiety.
While skin conductance effectively measures the intensity of physiological arousal, it does not differentiate between specific emotions. Both strong positive emotions like excitement and strong negative emotions like fear or anger produce similar increases in conductance, as both are states of heightened arousal.