Galvanic Skin Response (GSR), also known as skin conductance (SC) or electrodermal activity (EDA), is a physiological measurement technique. It assesses changes in the skin’s electrical properties, providing insights into emotional state and arousal levels. This non-invasive method detects unconscious bodily reactions to various stimuli.
The Science Behind GSR
GSR operates on the principle that skin’s electrical conductivity changes in response to sweat gland activity. The human body contains millions of sweat glands, with a particularly high concentration on the palms of the hands and soles of the feet. These eccrine sweat glands are primarily responsible for the measurable changes in skin conductivity. Unlike sweat glands involved in thermoregulation, their activity is largely influenced by emotional and physiological arousal.
The activation of these sweat glands is controlled by the sympathetic nervous system, a part of the autonomic nervous system. This system is responsible for the body’s “fight or flight” response, preparing the body for action during perceived threats or excitement. When arousal occurs, the sympathetic nervous system stimulates these sweat glands, increasing moisture on the skin surface. This moisture changes the balance of ions, allowing electrical current to flow more readily and increasing skin conductance.
GSR measurements are obtained by placing two non-invasive electrodes, often silver/silver-chloride (Ag/AgCl), on the skin, typically on the fingers or palm. A small, constant, low voltage current passes between these electrodes. The device then measures changes in skin conductivity, which are expressed in micro-Siemens (μS).
What GSR Readings Indicate
GSR readings primarily indicate the intensity of physiological or emotional arousal. An increase in skin conductance signifies heightened arousal, stemming from states such as stress, excitement, attention, or cognitive load. For instance, a sudden spike in GSR might occur when an individual is startled or experiences a strong emotional reaction. Conversely, a decrease or stable GSR reading suggests relaxation or a lack of significant engagement.
GSR measures the intensity of an arousal response, not the specific type of emotion. For example, it cannot differentiate between positive emotions like joy and negative emotions like fear; both increase skin conductance due to heightened arousal. This is because the underlying physiological mechanism—sweat gland activity controlled by the sympathetic nervous system—responds to any significant emotional or cognitive activation. Therefore, while GSR provides objective insights into unconscious reactions, it often requires context or combination with other measures to infer specific emotional valence.
Common Applications of GSR
Galvanic Skin Response is widely utilized across various fields to gain objective insights into human emotional and physiological states. In psychological and neuroscience research, GSR serves as a tool to study emotional responses, stress levels, cognitive workload, and attentional processes. Researchers use it to understand how individuals react physiologically to different stimuli, such as images, sounds, or tasks. This provides data on unconscious reactions not captured through self-reports.
GSR also finds significant application in biofeedback therapy, where individuals learn to consciously control their physiological responses. By providing real-time feedback on skin conductance, GSR biofeedback helps individuals manage stress, anxiety, and emotional instability. It has been explored as a complementary approach for conditions like epilepsy, chronic headaches, and certain psychiatric disorders, including anxiety and post-traumatic stress disorder (PTSD), by helping patients recognize and regulate their arousal.
In marketing research, GSR is employed to gauge consumer reactions to advertisements, products, and brand experiences. By monitoring changes in skin conductance, marketers can identify elements that evoke strong emotional engagement, helping to design more effective campaigns. While GSR has historically been associated with polygraph (lie detection) tests, the scientific community holds reservations about its reliability for determining truthfulness. Polygraphs measure multiple physiological responses, and GSR is just one component, with its fluctuations indicating arousal rather than deception itself.
Factors Influencing GSR
Several internal and external factors can influence Galvanic Skin Response readings, making controlled environments important for accurate measurements. Environmental conditions play a role, with factors such as room temperature and humidity affecting sweat gland activity and, consequently, skin conductance. Significant changes in ambient temperature, for example, can produce artifacts or false readings.
Individual physiological differences also contribute to variations in GSR. These include unique skin characteristics, hydration levels, and the use of certain medications. Each person has a different baseline skin conductance level, which can fluctuate. Therefore, GSR is often interpreted as a measure of relative change rather than an absolute indicator of an emotional state.
Psychological factors, such as a person’s level of attention, fatigue, or anticipation, can also impact readings. Even sudden physical movements or pulling on electrode wires can generate movement artifacts, which may be mistaken for genuine arousal responses if not properly identified. Researchers must carefully control these variables and establish a baseline to ensure the reliability and accuracy of GSR measurements, allowing for meaningful interpretation of changes in skin conductance.