Galvanic Skin Response (GSR), also known as electrodermal activity (EDA) or skin conductance (SC), is a physiological phenomenon reflecting changes in the electrical properties of the skin. This non-invasive measure primarily indicates the activity of eccrine sweat glands, which are influenced by the body’s automatic responses. It provides insights into internal states without conscious effort.
The Science Behind the Response
Galvanic skin response involves the sympathetic nervous system, part of the autonomic nervous system. This system prepares the body for “fight or flight” actions. When active, it stimulates eccrine sweat glands, especially on the palms and soles of the feet.
Increased sympathetic activity leads to greater sweat secretion. Sweat contains water and electrolytes, making it electrically conductive. As sweat fills the glands and is secreted onto the skin, its electrical resistance decreases and conductivity (conductance) increases. This allows electrical current to flow more readily.
Skin conductance directly reflects eccrine sweat gland activity, modulated by subconscious sympathetic nervous system responses. This physiological link makes GSR a tool for assessing changes in internal states.
Measuring Skin Conductance
Measuring galvanic skin response involves placing two electrodes on the skin, typically on areas with a high density of eccrine sweat glands, such as the fingertips, palms, or soles of the feet. A small, imperceptible electrical current is passed between these electrodes.
The device detects and quantifies changes in skin conductance, commonly expressed in microsiemens (µS). The absolute value of skin conductance can vary significantly, so the change from a baseline level carries meaning in GSR measurements.
Researchers record a baseline reading to establish a starting point. As a person responds to various internal or external events, fluctuations in skin conductance are tracked in real-time. These fluctuations indicate shifts in physiological arousal, providing objective data on immediate reactions.
What Galvanic Skin Response Reveals
Galvanic skin response fluctuations are closely linked to physiological arousal. This arousal stems from various internal or external stimuli, leading to changes in sweat gland activity. Exposure to emotionally significant events, for instance, can trigger measurable alterations in skin conductance.
GSR reflects the intensity of an emotional state, but it does not distinguish between specific emotions. An increase in skin conductance indicates general arousal, associated with excitement, fear, stress, or attention. Both positive and negative stimuli can elicit a similar increase in arousal and, consequently, in skin conductance.
Beyond emotional responses, GSR also provides insights into cognitive states, such as cognitive load or mental effort. Demanding mental tasks can increase sympathetic nervous system activity, leading to measurable changes in skin conductance. This response is an automatic reflection of the body’s readiness to react.
Practical Uses of GSR Technology
Galvanic skin response technology is utilized in diverse fields for objective insights into human physiological and psychological states. In psychological research, GSR is a tool for studying emotional responses, stress levels, and attentional processes. It allows researchers to observe unconscious physiological reactions to various stimuli.
Biofeedback therapy frequently incorporates GSR, enabling individuals to learn to control their physiological responses. By receiving real-time feedback on their skin conductance, people can practice relaxation techniques and develop strategies to manage stress, anxiety, or emotional instability. This approach helps individuals gain awareness and influence over their autonomic nervous system.
GSR also finds application in commercial sectors, such as marketing and consumer research. Companies use GSR to assess emotional reactions to products, advertisements, or user interfaces. In human-computer interaction, GSR measurements can indicate a user’s cognitive load or frustration. Historically, GSR was also part of polygraph tests, often referred to as “lie detection”. However, its use for this purpose has faced significant limitations, as GSR indicates general arousal rather than specific deception.