GSR, or galvanic skin response, is the measurable change in your skin’s ability to conduct electricity when you experience emotional arousal, stress, or surprise. When something triggers your nervous system, your sweat glands activate slightly, and that thin layer of moisture makes your skin a better electrical conductor. This tiny shift can be picked up by sensors on the skin’s surface, giving researchers and clinicians a real-time window into your body’s automatic stress responses.
The term “galvanic skin response” is the older name for what scientists now call electrodermal activity (EDA). You’ll see both terms used interchangeably, along with “skin conductance,” but they all describe the same phenomenon.
How GSR Works in Your Body
GSR is driven entirely by your sympathetic nervous system, the part responsible for your fight-or-flight response. When you encounter something emotionally significant, whether it’s a startling noise, a stressful question, or an exciting image, your brain sends a signal through the sympathetic nervous system to the eccrine sweat glands. These are the sweat glands found across most of your body, with especially high concentrations on your palms and fingertips.
The glands don’t need to produce visible sweat for GSR to register. Even a microscopic increase in moisture changes the skin’s electrical properties. Dry skin has much higher electrical resistance than slightly damp skin, so when your sweat glands become even a little more active, the skin’s conductance rises. Sensors placed on the skin detect this shift, and that data gets recorded as your galvanic skin response. The whole process is involuntary. You can’t consciously suppress or fake it, which is what makes it useful as a measure of genuine physiological arousal.
Two Components of the Signal
Researchers break GSR into two distinct parts. The first is the skin conductance response (SCR), a quick spike that happens in reaction to a specific event. If someone shows you a disturbing photograph, for example, your SCR would appear 1 to 4 seconds later and peak between 3 and 6 seconds after the image appeared. These phasic spikes indicate that your nervous system detected something novel or emotionally significant and is processing it.
The second component is the skin conductance level (SCL), which reflects your baseline arousal over a longer period. Rather than reacting to a single moment, SCL captures your average sweat gland activity across minutes or hours. Someone who is generally anxious during a task will show a higher SCL than someone who feels relaxed, even if neither experiences a dramatic spike. Together, these two components give researchers both the moment-by-moment reactions and the overall emotional tone of an experience.
What GSR Can and Cannot Tell You
GSR is a reliable indicator of arousal intensity, but it has a significant blind spot: it cannot distinguish between positive and negative emotions. A spike in skin conductance looks the same whether you’re thrilled or terrified. Your nervous system ramps up sweat gland activity in response to any strong emotion, so researchers typically pair GSR with other measures like facial expression analysis, heart rate, or brain imaging to determine whether the arousal is pleasant or unpleasant.
External factors can also muddy the data. Ambient temperature, humidity, and even room noise can influence readings. This is why controlled studies typically hold room temperature between 22 and 23°C and minimize environmental distractions. Skin thickness and hydration levels vary between individuals too, which means raw GSR numbers from one person aren’t directly comparable to another’s without careful calibration.
GSR in Lie Detection
The most widely known application of GSR is the polygraph, or “lie detector” test. Traditional polygraphs measure three physiological signals simultaneously: respiratory patterns, cardiovascular activity, and electrodermal response (GSR). Of these three, GSR has historically been the most consistently scored by examiners and, when inconclusive results are removed, the most accurate single channel for distinguishing truthful from deceptive responses.
That said, polygraph testing remains scientifically controversial. The core problem is that GSR measures arousal, not deception. A truthful person who feels anxious about being accused can produce the same spikes as someone who is lying. The polygraph works better than chance, but it is far from infallible, which is why polygraph results are inadmissible in many courts.
Medical Applications
GSR has found a meaningful role in epilepsy monitoring. Seizures, particularly generalized tonic-clonic (grand mal) seizures, trigger strong activation of the autonomic nervous system, producing sharp increases in skin conductance. In a study of patients with epilepsy using a watch-like EDA sensor, sharp increases in skin conductance were noted at the onset of all seizures monitored, with convulsive seizures producing the most dramatic spikes.
This led to the development of wrist-worn devices designed to detect seizures in real time. One such device, the Embrace wristband by Empatica, received FDA approval for detecting generalized tonic-clonic seizures. In a study of 69 patients, the device achieved 95% sensitivity with a false alarm rate of roughly one false positive every five days. For people with epilepsy who live alone or whose seizures occur during sleep, this kind of passive monitoring can be genuinely life-saving by alerting caregivers.
Marketing and Consumer Research
Neuromarketing researchers use GSR to measure subconscious emotional reactions to advertisements, product designs, and brand experiences. Because people often can’t accurately report how an ad made them feel (or don’t want to), skin conductance offers a way to capture real-time arousal that bypasses self-reporting bias. GSR sensors are relatively inexpensive and easy to set up compared to brain imaging, which has made them one of the most common tools in commercial neuromarketing studies alongside eye tracking.
The limitation here mirrors the general one: GSR tells a marketer that a viewer had a strong reaction to a particular moment in a commercial, but not whether that reaction was excitement, confusion, or disgust. Companies typically combine GSR data with eye tracking (to see what the viewer was looking at during the spike) and sometimes EEG (to get a rough sense of whether the emotional valence was positive or negative).
Wearable GSR Sensors
Consumer wearables that track electrodermal activity have become increasingly common, with devices ranging from research-grade wristbands to features embedded in smartwatches. These sensors work on the same principle as laboratory equipment: two small electrodes in contact with the skin measure conductance changes throughout the day.
Accuracy varies. One ongoing challenge is that gold-standard recording and processing procedures for EDA don’t exist yet. Different devices use different electrode placements, sampling rates, and algorithms, which means results from one wearable aren’t always comparable to another or to lab-grade equipment. If you’re using a consumer device that reports “stress” scores based on EDA, treat those numbers as rough trends rather than precise measurements. They’re useful for noticing patterns over days or weeks, but a single reading on a given afternoon doesn’t carry much diagnostic weight.