GSR vs EDA: A Simple Introduction to Galvanic Skin Response and Electrodermal Activity

What galvanic skin response sensors measure, how electrodermal activity is defined, where each term is used, and why these signals are useful.

What does a GSR sensor measure?
A Galvanic Skin Response (GSR) sensor measures changes in the skin's electrical conductance that occur when eccrine sweat glands are activated by the sympathetic nervous system. In direct terms, when arousal rises (for example due to effort, surprise, or cognitive load), tiny amounts of sweat change how well the skin conducts electricity. This is why GSR is often used as a proxy for physiological arousal, not for specific emotions. See: Critchley 2002, Posada-Quintero & Chon 2020.

EDA vs GSR: which name is correct?
Electrodermal Activity (EDA) is the umbrella term preferred in the psychophysiology literature and publication standards. It covers several related measures, including skin conductance and skin potential. 'GSR' is the older term and is still common in engineering, hobbyist, and historical contexts, but modern scientific writing generally uses 'EDA.' Good sources: Society for Psychophysiological Research publication recommendations (Boucsein et al., 2012; Wiley abstract) and the practical guide by Braithwaite et al..

What information is in an EDA/GSR signal?

• Tonic level (SCL): the slow baseline level of skin conductance that drifts over minutes.
• Phasic responses (SCR or EDR): rapid, transient increases time-locked to stimuli or occurring spontaneously.
• Event-related vs non-specific responses: SCRs can be linked to specific events, or appear without a labeled trigger.
• Common units and thresholds: conductance is reported in microsiemens (µS). A frequently used threshold for counting a valid SCR is about 0.01 µS (methodologies vary by study).
  References for definitions and thresholds: Boucsein et al., 2012; Braithwaite guide.

Where on the body is EDA measured?

• Preferred sites: fingers (distal phalanges) or the palm because of high density of eccrine sweat glands.
• Alternative sites: when hands are busy or not practical, researchers explore wrist, forearm, chest, or other locations; signal quality and artifacts can differ by site.
  See placement guidance in Boucsein et al., 2012 and an example evaluation of alternative sites in Gamboa et al., 2025.

Why is EDA useful?

• Stress and workload sensing for research, adaptive interfaces, and coaching.
• Biofeedback to help users learn self-regulation strategies (for example, relaxation training or seizure-related protocols).
• Affective and HCI studies to understand engagement, surprise, or cognitive load.
• Health and behavior research alongside other signals (heart rate, respiration) in lab and wearable setups.
  Overviews and examples: stress-detection review in wearables (Sensors 2024), EDA biofeedback and epilepsy (Schach et al., 2022), and applications reviews (Posada-Quintero & Chon 2020).

Quick glossary

• EDA: Electrodermal Activity, the preferred umbrella term in research.
• GSR: Galvanic Skin Response, an older term still used in hobbyist and historical contexts.
• SC / SCL / SCR: Skin Conductance, Skin Conductance Level (tonic), Skin Conductance Response (phasic).
• EDR: Electrodermal Response, often used interchangeably with SCR.
• Exosomatic vs endosomatic: measuring with applied current/voltage vs measuring intrinsic skin potentials.

A few links to get started

• Publication standards and methods: Boucsein et al., 2012 SPR report
• Practical 'how to' notes: Braithwaite et al., A Guide for Analysing EDA
• Physiology and applications overview: Critchley 2002, Posada-Quintero & Chon 2020
• Placement alternatives: Gamboa et al., 2025
• Device testing concept: EDA patient simulator, PLOS One 2020