The skin conductance response, also known as the electrodermal response (and in older terminology as "galvanic skin response"), is the phenomenon that the. Electrodermal activity (EDA) is the property of the human body that causes continuous variation in the electrical characteristics of the skin. Historically, EDA has also been known as skin conductance, galvanic skin. Skin conductance (SC) is normally measured with 8mm diameter silver/silver chloride electrodes positioned on the medial phalanx of the index and middle.
Hermann later demonstrated that the electrical effect was strongest in the palms of the hands, suggesting that sweat was an important factor. Vigouroux France, , working with emotionally distressed patients, was the first researcher to relate EDA to psychological activity. In in Russia, Ivane Tarkhnishvili observed variations in skin electrical potentials in the absence of any external stimuli, and he developed a meter to observe the variations as they happened in real time.
The scientific study of EDA began in the early s. One of the first references to the use of EDA instruments in psychoanalysis is the book by C. Jung entitled Studies in Word Analysis , published in The controversial Austrian psychoanalyst Wilhelm Reich also studied EDA in his experiments at the Psychological Institute at the University of Oslo, in and , to confirm the existence of a bio-electrical charge behind his concept of vegetative, pleasurable "streamings".
By , more than articles on electrodermal activity had been published in professional publications, and today EDA is regarded as the most popular method for investigating human psychophysiological phenomena. Skin conductance is not under conscious control. Instead, it is modulated autonomously by sympathetic activity which drives human behavior, cognitive and emotional states on a subconscious level. Skin conductance, therefore, offers direct insights into autonomous emotional regulation.
Human extremities, including fingers, palms, and soles of feet display different bio-electrical phenomena. They can be detected with an EDA meter, a device that displays the change electrical conductance between two points over time.
The two current paths are along the surface of the skin and through the body. Active measuring involves sending a small amount of current through the body. Some studies include the human skin's response to alternating current, including recently deceased bodies.
There is a relationship between emotional arousal and sympathetic activity, although the electrical change alone does not identify which specific emotion is being elicited. The amount of sweat glands varies across the human body, being highest in hand and foot regions — sweat glands per cm2. A correctly calibrated device can record and display the subtle changes. The combined changes between electrodermal resistance and electrodermal potential make up electrodermal activity.
Galvanic skin resistance GSR is an older term that refers to the recorded electrical resistance between two electrodes when a very weak current is steadily passed between them. The electrodes are normally placed about an inch apart, and the resistance recorded varies according to the emotional state of the subject.
Galvanic skin potential GSP refers to the voltage measured between two electrodes without any externally applied current. It is measured by connecting the electrodes to a voltage amplifier.
This voltage also varies with the emotional state of the subject. A painful stimulus such as a pinprick elicits a sympathetic response by the sweat glands, increasing secretion. Although this increase is generally very small, sweat contains water and electrolytes, which increase electrical conductivity, thus lowering the electrical resistance of the skin.
These changes in turn affect GSR. Another common manifestation is the vasodilation dilation of blood vessels in the face, referred to as blushing, as well as increased sweating that occurs when one is embarrassed. EDA is highly responsive to emotions in some people.
Fear, anger, startled response, orienting response, and sexual feelings are among the reactions that may be reflected in EDA. These responses are utilized as part of the polygraph or lie detector test. EDA in regular subjects differs according to feelings of being treated fairly or unfairly, but psychopaths have been shown to manifest no such differences. EDA is a common measure of autonomic nervous system activity, with a long history of being used in psychological research.
Critchley, Chair of Psychiatry at the Brighton and Sussex Medical School states, "EDA is a sensitive psychophysiological index of changes in autonomic sympathetic arousal that are integrated with emotional and cognitive states. Oftentimes, EDA monitoring is combined with the recording of heart rate, respiratory rate, and blood pressure, because they are all autonomically dependent variables.
EDA measurement is one component of modern polygraph devices, which are often used as lie detectors. The E-meter used by the Church of Scientology as part of its practice of " auditing " and " security checking ", is a custom EDA measurement device. External factors such as temperature and humidity affect EDA measurements, which can lead to inconsistent results. Internal factors such as medications and hydration can also change EDA measurements, demonstrating inconsistency with the same stimulus level.
Also, the classic understanding has treated EDA as if it represented one homogeneous change in arousal across the body, but in fact different locations of its measurement can lead to different responses; for example, the responses on the left and right wrists are driven by different regions of the brain, providing multiple sources of arousal; thus, the EDA measured in different places on the body varies not only with different sweat gland density but also with different underlying sources of arousal.
These show the complexity of determining the relationship between EDA and sympathetic activity. From Wikipedia, the free encyclopedia. Retrieved 20 October The purpose of the analyses reported here is to assess whether the practice of scoring the FIR and SIR separately provides a better assessment of SC conditioning than simply obtaining the peak SC response regardless of where the peak falls within the CS-UCS interval i.
To accomplish this aim, we analyzed the SC data obtained during a differential aversive conditioning procedure administered within a large study of police and firefighter trainees conducted by the third author and members of his research group. Police and firefighter trainees were recruited from the: Participants were part of a larger project that will prospectively examine predictors for the risk of developing posttraumatic stress disorder PTSD in police and firefighters.
The average age and education level of the sample were Written informed consent was obtained from all participants in accordance with the requirements of the Partners Healthcare System Human Research Committee.
The SC electrodes were separated by 14 mm, as determined by the width of the adhesive collar. The experimental session took place in a humidity- and temperature-controlled room located in quiet areas of the respective training academies. Due to space limitations, it was necessary to locate the participant, laboratory equipment, and technician in the same room. A screen was placed so that the participant could not see the recording equipment and technician during the conditioning procedure.
The participant was seated in a chair placed 4 feet in front of a monitor that was used to display the CSs. The range of UCS intensities was 0. Because conductive properties of the hand affect the subjective experience of shock, different participants may have found the same level of shock to be relatively more or less aversive.
During the baseline period, which will last 5 min, we will check our instruments and you should try to relax. During this phase two different colored circles will be presented on the monitor.
You should sit quietly and look at each colored circle as it is presented. During this phase the colored circles will be presented again, and some of them will be followed by the electric stimulus.
Again, you should sit quietly and look at each colored circle as it is presented. During this phase you will see more colored circles. However, you will no longer receive any electric stimulation. Please continue to sit quietly and look at each colored circle as it is presented. It is important that you watch the screen at all times.
Do you have any questions? After the subject indicated readiness to proceed, the technician activated the computer, which took over administration of the experiment. After a 5-min resting period, the three phases of the experiment were initiated. During each phase, the CS duration was 8 s, and the intertrial intervals ITIs ranged from 15—25 s, with the duration of each ITI determined at random by the computer.
Skin conductance response scores were analyzed in two ways: Scoring criteria for FIR and SIR were guided by our reading of the older literature, our presumptions about scoring decisions made by previous investigators that were not explicitly elaborated in the published reports, and practical considerations from inspection of the present data.
Below, we have tried to provide a concise, but clear, description of the method arrived at for scoring the FIR and SIR. However, we suffer no delusion that this is the final answer and that some readers will not argue with one or more of our interpretations and assumptions.
A copy of the Mathematica-based scoring algorithm and program we developed is available on request; use of this program requires access to Mathematica 6 Wolfram Research Inc. This scoring algorithm identifies response onset for the FIR and SIR by finding the point of maximum curvature of the SCL data within a pre-specified onset window and then stepping forward or backward until the slope changes from negative to positive or positive to negative.
This point of slope change defines the response onset. A response peak is found by locating the highest SC value after the identified onset and within the window specified for the peak. In order for a response to be scored, neither its onset nor peak can be located at the first or last data point in their respective window. If this occurs, the window is shrunk and the algorithm looks for a new onset or peak. An exception to this is when the data are flat in the vicinity of an onset that occurs at the first data point, in which case the requirement is that the data remain flat for 0.
The search for an onset or peak continues until the lowest onset SCL value and highest peak SCL value are identified in their respective windows, or a window reaches zero width. A zero-width window indicates that an onset or peak cannot be found and no response for the interval is calculated.
If the value of the last data point within the SIR window exceeded the identified peak, that value was substituted for the SIR peak value. For the present study, the mathematical expression used to characterize curvature of the SC data was closely approximated by the second derivative, because the first derivative was found to be much less than one.
As determined from the extant literature, windows for potentially locating a response onset and peak were specified as follows for the FIR and SIR. For the FIR, we required that the inflection point of a response onset occur within 1—4 s, and that the response peak occur within 2—6 s, following CS onset. For the SIR, we required that the inflection point of response onset occur within 4—8 s, and that the response peak occur within 5—9.
Skin conductance data were not collected during the actual UCS presentation i. Consequently, the SIR peak could be slightly underestimated if it occurred within the 0. The SIR window, even though it extends to 9.
When the FIRs and SIRs were averaged over trials, zero entries were used for trials that produced no identifiable response. A square-root transformation was applied to all response scores. Each line denotes the average SC levels over time for each of the 10 trials. In addition, 18 participants did not exhibit a SIR on any acquisition trial and four participants did not exhibit a FIR on any acquisition trial, but did exhibit a SIR on at least one of these trials.
For the FIR, mean onset latency ranged from 1. For the SIR, mean onset latency ranged from 6. Analyses of variance ANOVA for repeated measures were conducted separately for the three phases of the procedure: See Table 3 and Figure 2 for a summary of these results.
All significance levels reported for analyses that included the Trials variable reflect the Greenhouse-Geisser correction; however, the original degrees of freedom are presented when reporting the statistical tests.
All significance levels reported for analyses that included the Trials effect reflect the Greenhouse-Geisser correction for violation of the sphericity assumption. However, in order to minimize possible confusion arising from different degrees of freedom being reported for similar analyses, we report the degrees of freedom associated with the unadjusted tests.
Skin conductance response magnitude showed an overall decrease over trials. The repeated-measures ANOVA for the EIR produced a significant Trials main effect, which appeared to have a repeated pattern of increases and decreases over the course of the trials.
Another set of analyses focused on testing individual differences between those who responded more strongly at the beginning of the CS-UCS interval FIR and those who responded more strongly towards the end SIR. Based on these data, participants were divided into two groups: Comparisons of these groups indicated that they did not differ on measures of psychological distress Derogatis, , depression Beck et al.
Based on our comprehensive review of the differential aversive conditioning literature and the cumulative findings from these studies, differential conditioned responses appear to be observable in both the FIR and SIR. In addition to this review, we addressed the utility of separately scoring the FIR and SIR through a secondary analysis of SC data obtained from a differential aversive conditioning procedure administered in the context of a large study of police and firefighter trainees.
The primary outcome of the secondary analyses is clearly evident in Figure 1 , where it can be seen that the SC responses to the 8-s duration conditioned stimuli are primarily characterized by a single, prominent peak that occurs around 3—4 s following CS onset.
It is worth noting that the latency of this peak remained remarkably stable across trials. As can be seen in the figure, there is almost no displacement of this peak from early to late trials.
However, a longer CS-UCS interval than that used in the present study, or more conditioning trials, may be necessary to reveal a progressive shift in the response peak, if one exists. Although Figure 1 suggests a single SC response peak, statistical analyses indicate that effect of differential conditioning can be detected in the SIR, as well as the FIR.
It is possible that the absence of a more distinctive SIR peak in the figures is due, at least in part, to greater variability in the SIR peak latency, i. This is further reflected in the effect sizes for differential conditioning, which were comparable for the three measures. These results support the use of either the FIR or EIR to detect differential aversive conditioning effects and suggest that there is no substantive difference between the scores generated by the method used to calculate the EIR and that used to calculate the FIR.
Both scoring methods seem capable of adequately representing conditioned SC responses generated by a differential aversive conditioning procedure that uses a long CS-UCS interval.
However, from an individual-differences perspective, individuals who show relatively larger FIRs, compared to those who show relatively larger SIRs, do not appear to differ on measures commonly thought to influence differential conditioning e. The lack of meaningful psychological differences between individuals who preferentially exhibit a FIR or SIR suggests that separate measurement of these two responses may be unnecessary.
This eliminates the risk of underestimating a larger CR when the onset or peak of the response occurs near a previously established boundary between the FIR and SIR or when the latency of the peak response shifts over trials. Second, from a practical standpoint, the method used to calculate the EIR reflects a much simpler way of scoring data.
This method, as applied in the present study, simply calculates a pre-stimulus-onset SC level by averaging data over a brief duration we used 2 s , identifies the highest SC level i. Because SC responses have relatively long onset latencies, it would also be reasonable to use the SC level immediately following stimulus onset e. Scoring is easily accomplished within one of the currently available spreadsheets e.
Most importantly, this method does not require undertaking the complex process of mathematically modeling SC data curves, identifying points of inflection that define a response onset and creating, or learning to use, software that can accomplish this process. Although there appear to be advantages to using the EIR rather than the FIR and SIR, it is important to note some potential limitations to the generalizability of our findings.
First, because there were only five acquisition trial pairs, we are unable to assess whether similar results would be observed for longer acquisition phases that included a greater number of trials. Similarly, because the CR extinguished very quickly for most participants, likely due to the extinction instructions, we were unable to assess the utility of the EIR vs.
Finally, because this dataset is derived from one study, it is possible that specific aspects of the procedures may have contributed to the results. In sum, based on the existing electrodermal conditioning literature and secondary data analysis, it appears that separating SC responses into FIR and SIR components in differential aversive conditioning studies may not be warranted.
Instead, use of the EIR to capture the SC response is recommended, at least in studies that administer relatively few acquisition trials. This research was supported by U. We would also like to express our appreciation to the police and firefighters for their willingness to participate.
National Center for Biotechnology Information , U. Author manuscript; available in PMC May Pineles , a, b Matthew R. Orr , c and Scott P. Author information Copyright and License information Disclaimer.
Address reprint requests to: The publisher's final edited version of this article is available at Psychophysiology. See other articles in PMC that cite the published article. Abstract Researchers examining skin conductance SC as a measure of aversive conditioning commonly separate the SC response into two components when the CS-UCS interval is sufficiently long.
Conditioning, Electrodermal response skin electric response , Scoring methods. Ext Interval 1 Interaction? Ext Interval 2 Main effect? Ext Interval 2 Interaction? Open in a separate window. Method Participants Police and firefighter trainees were recruited from the: Procedure The experimental session took place in a humidity- and temperature-controlled room located in quiet areas of the respective training academies.
Once the UCS level was established, the subject was given the following instructions: Response Scoring Skin conductance response scores were analyzed in two ways: Acknowledgments This research was supported by U. Cognitive therapy of depression. Effects of conditioned stimulus pre-exposure on human electrodermal conditioning to fear-relevant and fear-irrelevant stimuli.
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SKIN CONDUCTANCE EXPLAINED
Jul 17, Skin conductance is not under conscious control. Instead, it is modulated autonomously by sympathetic activity which drives aspects of human. Skin conductance (SC) has a simple curve form always with an initial rapid increase and a slower recovery. SP curves are more complicated. Many papers, such. The skin conductance response (SCR) is an indirect measure of sympathetic autonomic activity that is associated with both emotion and attention. In humans.