Electrodermal activity (EDA) refers to the continuous variation in the electrical characteristics of the skin. This physiological phenomenon is associated with the skin’s ability to conduct electricity, which changes in response to internal states. EDA serves as a non-invasive method to gauge physiological arousal. It has been known by various terms historically, including skin conductance and galvanic skin response (GSR), but EDA is now the standardized term.
The Science Behind Electrodermal Activity
The physiological foundation of EDA primarily involves the eccrine sweat glands, which are distributed across the human body, with the highest concentrations found on the palms of the hands, fingertips, and soles of the feet. These glands are unique because they are exclusively innervated by the sympathetic branch of the autonomic nervous system. This direct neural connection means that changes in sympathetic nervous system activity directly influence sweat gland function.
When a person experiences emotional or cognitive arousal, the sympathetic nervous system becomes more active. This increased activity triggers the eccrine sweat glands to produce minute amounts of sweat. Sweat contains water and electrolytes, which increase the skin’s electrical conductivity. Therefore, by monitoring these subtle shifts in skin conductance, researchers can infer changes in sympathetic nervous system arousal.
How Electrodermal Activity is Measured
Measuring EDA involves placing electrodes on specific areas of the skin, most commonly the fingers, palms, or soles of the feet. These electrodes are typically made of silver-chloride (Ag/AgCl) due to their stability and ability to accurately transmit signals from ionic activity. A small, imperceptible voltage is applied across these electrodes, and the resulting current or conductance is measured.
The devices used to capture EDA data, such as galvanometers or specialized EDA sensors, record these changes in electrical conductance over time. The measurements are typically expressed in units of microsiemens (µS) or micromhos (µmho). These devices can store data internally, transmit it wirelessly via Bluetooth, or send it through a wired connection to a computer for analysis.
What Electrodermal Activity Reveals
Changes in electrodermal activity serve as a direct indicator of sympathetic nervous system arousal. This arousal is closely tied to a range of internal states, including emotional experiences, cognitive processing, attentional shifts, and stress levels. When an individual encounters a stimulating event, whether it is exciting, frightening, or mentally demanding, there is typically an increase in sympathetic activity, which manifests as a rise in EDA.
Elevations in EDA often correlate with heightened emotional intensity, such as excitement, fear, or surprise, as well as increased cognitive load or mental effort. It is important to note that EDA primarily measures the intensity of physiological arousal rather than the specific emotional valence (whether an emotion is positive or negative). Both positive and negative stimuli can lead to an increase in skin conductance, reflecting a general state of activation rather than the specific feeling itself.
Practical Applications of Electrodermal Activity
Electrodermal activity is widely utilized across various fields. In psychological research, EDA is a common tool for studying emotional responses, attention allocation, and cognitive processes, helping scientists understand how individuals react to different stimuli. It is also employed in biofeedback and stress management programs, helping individuals regulate arousal to reduce anxiety.
In clinical settings, EDA can serve as a supplementary tool for assessing conditions such as anxiety disorders or phobias, offering objective data to complement self-reported symptoms. Beyond traditional research and clinical uses, EDA finds application in neuromarketing and user experience (UX) research. By measuring emotional responses to advertisements, products, or digital interfaces, companies gain insights into consumer engagement. As wearable technology advances, EDA monitoring is becoming more accessible for continuous, real-world data collection, expanding its utility in diverse settings, including healthcare and human-computer interaction.