Electrodermal activity is what lie detectors measure: what is it?

A talk with psychologist Christopher Moyer about electrodermal activity (EDA), also known as galvanic skin response (GSR), which is what lie detectors measure. This is a reshare of a 2019 episode. A transcript is below.

Topics discussed include: What are spikes in electrodermal activity actually telling us? We talk about its use in lie detectors. We talk about lowerings in skin conductance and what that indicates. We talk about the Scientology “e-meter.” We talk about the nature of stress; and how there can be good and bad stress. We talk about poker and gambling, including some gambling-related studies that measured electrodermal activity. 

Episode links:

For resources and studies related to this talk, see the original post.


Zach Elwood:

Welcome to the People Who Read People podcast, with me, Zach Elwood. This is a podcast about understanding people better: the things they do, and the things they say. You can learn more about it, and sign up for a premium subscription, at my site

I’m currently spending my free time working on my Defusing American Anger book, which you can learn more about at Because I’m working on that, I’m sharing some early episodes of the podcast from back in the day; these are episodes I think are pretty good and interesting but haven’t got many listens because I released them when my audience was much smaller.

I’m going to share an interview I did with psychologist Christopher Moyer, about electrodermal activity, aka galvanic skin response. This is the skin response that lie detectors measure. I was thinking about this episode recently because I wanted to interview someone about lie detectors and the controversies around them, so I thought sharing this one might be a good lead in to that.

Topics we talk about include: what do spikes in electrodermal activity really tell us? What does research say about what that tells us? Clearly spikes can indicate activation of our nervous system, but what exactly is going on there? We talk about its use in lie detectors, and how lie detectors are supposed to be able to detect lies. I ask him if there can be lowerings in skin conductance and what that indicates. We talk about the nature of stress; and how there can be good and bad stress. Can it be used to measure whether someone is experiencing pain? Chris is a poker player and so we get on the topic of poker, and also talk about some gambling-related studies that involve electrodermal activity. And we get on quite a few other topics; it was an interesting talk and I think you’ll enjoy it.

Hello, and welcome to the People Who Read People podcast. I’m your host Zach Elwood. Today is December 19th, 2019. Today, I’ll be talking to Dr. Christopher Moyer Ph.D. Dr. Moyer is a counseling psychologist with expertise in treatment research and has published research on the anxiety-reducing effects of massage therapy and the neurological effects of meditation. He also happens to be an avid poker player and he began playing seriously in 1994. And it’s actually through poker that I met him online through poker-related social media. He’s taught at the University of Illinois, the University of Wisconsin Stout, the University of Denver, and he’s currently a visiting assistant professor of psychology at Augustana College in Rock Island, Illinois, where he teaches the course Psychology of Poker. He also is the lead author of the most highly cited article on massage therapy Research.

Welcome to the show, Dr. Moyer.

Christopher Moyer: Thank you. Pleased to be here.

Zach: Thanks for coming on. Today we’re going to talk about galvanic skin response, also known as electrodermal activity, EDA, and Dr. Moyer has used this technology in his research. Dr. Moyer, can you talk a little bit about what electrodermal activity is and what it measures? 

Christopher: Sure. Electrodermal activity, which also goes by other names, in the past it was called galvanic skin response and electrodermal resistance and there’s a bunch of ways to refer to it. But essentially, what the method is a way of measuring the activity of the sweat glands in a person’s palm. You can do it in other parts of the body too, but the palm is especially good for it because it is very densely packed with sweat glands. And the reason that is interesting, the reason we’d want to measure the sweat in a person’s palm or more accurately the activity of the sweat glands– it doesn’t even have to be visible sweat– is because those sweat glands are connected directly to the autonomic nervous system. And so if we want to know what is going on inside a person’s body as it relates to arousal, we can get a very direct and very rapid assessment of that by measuring the changing electrical resistance in the person’s hand. And that changes because sweat is a saline solution and so as the sweat rises or falls in the sweat glands, the electrical resistance of the person’s skin changes. This is a very rapid way of getting a measurement of what the person’s autonomic nervous system is doing. The autonomic nervous system is that branch of the nervous system that we do not have direct conscious control over. It is regulating our breathing and our body temperature and it is controlling the balance of our sympathetic and parasympathetic nervous system and it’s responsible for the fight or flight response, which most people have heard of, that ability to become very excited very rapidly in response to something stressful in our environment and it mobilizes us to fight or to flee in response to something that could be threatening.

Zach: So the response can be in response to anything that basically arouses you in some way like anxiety, pain, distress, embarrassment, fear, anger. 

Christopher: Yes. 

Zach: In short, would you say… I mean, I’ve seen it referred to as autonomous arousal and that’s just a way to say it’s exciting you in some way. Is that kind of accurate to phrase it that way?

Christopher: Yes, if by exciting, we mean physiologically. Whether the person would find it subjectively exciting is a separate issue, but what it is definitely telling us is that the person’s body is mobilizing to respond to a threat.

Zach: Yeah, and I saw a referenced quote on Wikipedia. It said that by 1972, more than 1500 articles on electrodermal activity had been published in professional publications. And today, EDA is regarded as the most popular method for investigating human psycho-physiological phenomenon. So it sounds like yeah, it’s a very respected way to measure that kind of arousal excitement.

Christopher: Yeah, there isn’t really any substantive controversy about what it’s measuring. Everyone agrees that we can measure the activity of the sweat glands and that this is an accurate representation of physiological arousal. Now, once you step a level beyond that, if we try to interpret that, then we can run into some controversy. So if a person’s physiological arousal increases, does that mean they are anxious? Does that mean they’re excited? Does that mean… It could mean a lot of different things. But at a more fundamental level, there’s very little to disagree about that it’s a way of measuring a person’s autonomic arousal.

Zach: And I guess when you do scientific research, you avoid drawing conclusions about what the underlying mechanisms are. All you can say is there was heightened electrodermal activity. You can’t draw too many conclusions based on that, even if you know that it’s some sort of arousal excitement. 

Christopher: Well, I think it depends. Depending on the context, you might be able to make reasonable inferences. Or you might be able to combine the EDA assessment with other things such as asking the person, either formally or in an unstructured way depending on the kind of research you’re doing, what their subjective experience is. So, it depends. I would not attempt to interpret an EDA trace alone and try to use that to know what’s going on in a person’s mind. But in conjunction with other things, one might be able to get closer at that. 

Zach: Right. Like if you had a study about measuring pain response, you can kind of put it in context of like, “Okay, we’re doing something painful, we can map it to the electrodermal activity. 

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Christopher: Yeah. In short, if you knew what the person was being subjected to, and then especially if you could have them report about their experience, you could use those things in combination to get at what their experience probably is.

Zach: Now, this is the same technology used in the lie detector, the polygraph. Is that right?

Christopher: It’s at least one of the channels in a polygraph test. I’m not directly… I’ve never used a polygraph in that term but I’ve used all the various technologies that a polygraph might use. As I understand it, someone who is operating a polygraph, they may be recording certainly electrodermal activity, but they may also be recording heart rate, breathing rate, and other channels that are also measures of autonomic arousal.

Zach: Yeah, I kind of wonder now that I don’t know what the actual definition of polygraph is. I don’t know if it’s a set definition of it has to include all these things that they’re measuring, or maybe it’s a kind of a broader term. I’m not really sure about that. 

Christopher: Yeah, I would suspect it’s a broader term. The word itself ‘poly’ suggests that you’re measuring several channels and you’re graphing them. Now whether there is a formal set that they always use, I would venture to guess there is not because the practice itself is, in my scientific opinion, a little bit dubious. I mean, it really gets at what we were just saying. You can record what’s going on in the person’s body that doesn’t necessarily tell you what’s going on in their mind or whether they’re trying to deceive you or not. So a lot of times, many people have a naive assumption that something like a polygraph is very accurate or very useful for lie detection, but it actually is not. 

Zach: Right. Because you’re having to draw so many interpretations about what is on the surface, just a kind of mysterious activity that could be… Like, if you get a positive response on a lie detector, it could be because you’re nervous for that question or it could be because you’re lying, etcetera, etcetera. Yeah. 

Christopher: Yes. 

Zach: This was something I wondered just looking at some electrodermal activity charts. Is there such a thing as negative spikes? Because I know you have a baseline amount of conductivity on your skin. So, is it possible to go below your baseline or is the measurement only a positive measurement? 

Christopher: I think I understand what you’re asking. You’re asking, could your electrodermal activity go down in response to something in your environment? 

Zach: Yeah. 

Christopher: Sure. Things that would be relaxing or deactivating should cause an EDA trace to go down. So in my own research, one of the things I’m most interested in is how people respond to massage therapy. And under the right conditions, we would expect that as massage continues, that a person’s autonomic arousal would decrease and that we would see this as a lowering of an EDA trace. Ultimately, there would be a baseline that you could not go below if that person’s sweat gland activity was to reach zero because they’re unconscious or something like that. Otherwise, I guess there’s an absolute baseline but in practice, you might see it go below their resting baseline. But it’s only going to go so far. 

Zach: I’d seen that you could separate the measurements into two types: the tonic and the phasic. And the tonic was more like the baseline underlying slowly changing levels versus the phasic, which was more like the rapidly changing levels. Does that make sense? Is that accurate?

Christopher: Yeah, you can use it in more than one way. So if you were trying to detect someone’s immediate response to something like in a polygraph, if you wanted to see if presenting them with certain information caused them to have a sudden spike in autonomic arousal, you can look for that. Or if you’re doing something like I was describing, like you want to see how a person’s body responds to 45 minutes of massage therapy, you can look at a much longer sampling of time and see if there is a more gradual trend. Both of those are valid ways of using it. 

Zach: Let’s talk a little bit about the work you’ve done. What kinds of—not just electrodermal activity measurements—but what has been the bulk of your work? 

Christopher: Most of what I’ve focused on is whether massage therapy is an effective treatment for anxiety and also for depression. I put anxiety ahead of that because I think that treating anxiety can often also treat depression as kind of a downstream effect that anxiety might be the most important thing for us to consider in these instances. So we’ve looked at… I’ve conducted a meta-analysis, which is a way of summarizing all of the existing studies. I’ve conducted a systematic review of whether massage therapy alters the stress hormone cortisol, which is closely related to some of the things we’re talking about in terms of autonomic arousal. I’ve conducted some laboratory research with normal persons and also with people who have anxiety disorders to see how their autonomic response is in response to massage therapy turns out to show some patterns that are a little different than one might assume. And then I’ve done various other projects. The things that unite my projects is that they’re usually related to anxiety or self-regulation. One time we did a meditation study to see if small amounts of meditation would alter brain activity. And then even in my hobbies, something like poker, I haven’t conducted any research on that. But when I’m thinking about something like that, I’m often thinking about how different situations might impact a person’s autonomic arousal. Or whether in a playing situation, whether there are things I ought to be able to look for like a change in the person’s breathing. All these kinds of things tie together. I’m pretty interested in anxiety and autonomic arousal and how those things pertain to treatment of anxiety and depression. 

Zach: You had said electrodermal activity was an unconscious autonomous response. But I’ve seen there’s some biofeedback machines they have that you basically are seeing the results of your measurements of electrodermal activity and then trying to get some kind of conscious control over it. Do you know much about that? Is that real? Or is that kind of…

Christopher: I can speak to that. And I’m going to make a point that I make to my students very often, which is sometimes I’m asked to review scientific manuscripts. A couple of years ago, I was reviewing a manuscript and the first sentence of this manuscript of this study that some other scientists wanted to publish stated unambiguously, “Human beings are unable to control their autonomic nervous system.” The sentence was something very direct like that, and I immediately thought to myself, “How could people studying this write something like that?” Now I knew what they meant. What they meant or what they had in mind is that we cannot directly influence your autonomic nervous system. So there are other branches of your nervous system that you have conscious control over. If you decide to move your arm, so long as you’re not injured or have paralysis, you decide to move your arm and it moves the way you want it to move. But what you can’t do is you can’t just will your heart rate to go up 50% or you can’t just will yourself to start sweating. Those things are under their own autonomous control. However, it would be a mistake to then say human beings cannot control their level of autonomic arousal. In fact, the opposite is true. You can understand most of human behavior as a function of people trying to regulate their arousal. And we do this by pursuing activities, we do this by consuming drugs, we do this by playing games, we do this by seeking out novelty. Pretty much all the things we do all the time are influencing our autonomic arousal. In doing that, we often are rewarded by experiencing a change in our subjective mood are in our emotional state. We get thrills. We get rewarded by changing our level of arousal. So… I forget what you asked me at first. 

Zach: The biofeedback machines. 

Christopher: Oh, right. Okay, so the biofeedback. Yeah, so it stands to reason. If you’re just sitting here and thinking to yourself, “Okay, what’s my electrodermal activity? Can I change this at all?” The answer would be probably no or not very effectively. But if you had it hooked up to a monitor such that you’ve now created a channel where you can see it, that at least introduces the possibility that you would be able to exert some feedback control over that. And thus, that’s why it’s called biofeedback. And yes, you’re able to do that. Now, whether you’re doing that directly in response to the monitor you’re looking at or whether it is a more general effect that the person is learning how to relax, which we’re all able to do to a greater or lesser extent, it would take a little bit of research to sort that difference out. But the principle behind biofeedback that you would create monitors so that a person could witness the activity of what is normally not under their control and thereby give them some access to it, that makes some sense and there’s some evidence that that will help a person to yield some control over that. 

Zach: Right. And the idea for the people that make and promote these products is that it’s a way for people to try to get in control of their anxiety by having something to focus on and something to try to see the effects of their mental state on and try to exert some control over their anxiety or whatever. 

Christopher: Yeah. Now, one of the problems with that is those things are often oversold. The people who are enthusiastic about them go too far in their claims. So I would place the value of something like that… I think there is some value in that kind of technology. But if you start talking to someone and they are talking about it like a panacea or extremely powerful method for that, they’re probably overstating at that point. The fact is we can do those things in the absence of biofeedback. So when people do something like a progressive muscle relaxation exercise or when people train themselves to do brief meditation, these are really kind of very similar practices absent to the biofeedback technology. 

Zach: Right. Because I would think if you were looking at your activity on the screen, you would be mentally playing around with different things kind of just relaxing, probably just focusing on the screen and relaxing and sitting in one place. I mean, you would eventually hit upon the things that work for you to relax. I would imagine so. I can see what you mean by it’s like an indirect thing. Is it because of their looking at the response of their activity or is it just because they’re playing around with different ways of being or something and one of them works. Which I guess that’s beneficial if that’s what happens. 

Christopher: And then there’s a separate question too, which is, might that be different for different people? There might be some people who find the display kind of hypnotic and mesmerizing and relaxing. And then there might be other people who, because they have a tendency towards anxiety, find a demand in that— 

Zach: Test-taking anxiety. One thing you had said was the heart rate was also something that wasn’t under conscious control. But people can raise their heart rate by imagining exercising and things like that, right?

Christopher: Right. When I say something like that, I’m overstating a little bit to make the point. So yeah, you have a little bit of control over that. But compare that to your somatic nervous system. If you decide to move your arm right now, it just moves under your control, whereas you can’t just will your heart rate to go up 40 beats a minute. I mean, you might be able to by thinking about something exciting. You might get it to go up a bit but you can’t just start it or stop it or double it or anything like that. 

Zach: I guess there’s the legends of yogis or Buddhist monks who can do that, but I have no clue if having that extreme control over your functions is a real thing.

Christopher: Yeah, you can’t. Those amazing stories are usually too amazing to be true. I’d put an asterisk on that because there are examples of people—Buddhist monks are a good example. They’ve been studied mostly at the University of Wisconsin– not the campus I was at, but the main campus, Wisconsin Madison– and some of what those lifetime practitioners of meditation are able to do that shows up in an MRI is amazing. You can see an incredible shift in brain activity. But that’s different than being able to just willfully increase your heart rate by 20% or 30% or decrease it by 20% or 30%. There might be cases of people who can exert a surprising… There’s always outliers but there’s also…

Zach: Yeah, generally not a known phenomenon for that.

Christopher: Yeah. There’s also the underlying physiology. For your body to work, your autonomic nervous system has to be able to function autonomously. And if it was possible for you to directly interfere with that, that would be bad. Not good. 

Zach: Yeah, really. Like you could just get in some sort of state and you accidentally hurt yourself or something. [chuckles]

Christopher: Yeah, you don’t, you don’t want to exert direct conscious control over that stuff. You want that stuff to take care of itself. 

Zach: Right, that makes sense. Let’s talk more about your work. What were you doing with electrodermal activity measurements in the massage therapy work? 

Christopher: Well, when I was at Wisconsin Stout, I became friends with a psychophysiologist, Mike Donnelly. He became a good friend of mine and he opened up a bunch of interesting ways for me to take the clinical research I was doing and extend it into psychophysiology and neuroscience. So one of the things that I had been thinking about for a long time was what is going on in the body when people are receiving something like a massage. There already was considerable evidence that massage therapy reduced anxiety pretty substantially. And people who are interested in this tend to just assume that it must be deactivating. That it’s reducing arousal and that reduction of arousal will show up as a reduction of stress hormones, and that that is yielding the clinical benefit of reduced anxiety. Now, the problem with that is even though the clinical results show this market decrease in anxiety, the effect on something like stress hormones is not there. And I’ve analyzed it back to front, up down, every single possible way. Massage therapy does not reduce stress hormones very much. This creates an interesting situation where you have a lot of people, including another scientist in the area, who’s consistently claiming that massage therapy first reduces the stress response in the body, and then that leads to a clinical effect of reduced anxiety. But the evidence doesn’t support that. 

So we started measuring people’s response of their autonomic nervous system to massage therapy in the lab and we had a control condition where the exact same people would enter the exact same lab. And everything was the same. They listened to the same music, the temperature was the same, they lay on the table the same way, they heard the same music. The only difference was sometimes when they showed up, they got a massage, and sometimes when they showed up, they did not get a massage. But everything else was the same. And if you do that and you record these autonomic variables like electrodermal activity and heart rate, you now have a pretty powerful way of assessing whether massage therapy is increasing or decreasing arousal. And it’s complicated. So at first, an intervention like massage therapy in the early parts of it increases arousal more than just laying there. But then gradually, people adapt to it and a relaxation response takes over. And across a one-hour massage, you tend to see that depending how you assess it, their arousal is decreased by this intervention. Now that’s in normal people. That’s in people who were selected according to having no health problems and are normal. But then we did this again and we selected people who met the criteria for anxiety disorders and saw something very, very interesting: which was receiving massage for people with anxiety disorders increased their autonomic arousal. It still decreased their anxiety. So when you asked them at the end of sessions how they felt and you had them complete a formal instrument to measure their anxiety, they said that their anxiety went down considerably. They never said anything like, “Oh, this was stimulating or I felt like this was revving me up or something.” They never said anything like that. They perceived it as relaxing and deactivating. And yet physiologically, it was more stimulating than the control condition of just laying there. 

This is just one example, but it points at the complicated nature of physiology to psychology. It’s not simply a matter that decreasing arousal will cause a person to feel relaxed or increasing arousal will cause a person to feel energized or tense or something. There’s a cognitive interpretation that takes place such that an increase in physiological arousal could be perceived as relaxation, or vice versa, depending on many different variables. So that’s some of the research that we did with this technology. And I’ve spoken about this at conferences and actually have it as my goal this coming semester to get the studies written up and published. They’ve been delayed a bit for various reasons that are not germane to what we’re talking about. But I’m excited to formalize those results and get them out there because they’re pretty interesting.

Zach: Was that a surprising finding when you saw that?

Christopher: Yeah, it definitely was. And if there’s anyone it shouldn’t have been too surprising to, it would have been me because of the previous meta-analytic work I’ve done. I should have maybe anticipated that possibility. And yet it was still surprising when we saw it in the results. So in a word, yeah, it’s a little bit surprising. But it also is consistent with some of the things that I’d thought about massage therapy and anxiety and autonomic arousal before. So, a mix.

Zach: I know there’s lots of theories you could make about why that was, but does one lead in your mind about why that would occur? Is there something going on consciously that it makes them uncomfortable because maybe the touches is new and weird to them? Maybe they aren’t used to that but they’re getting benefits on some unconscious level that it’s good for their body. Could you talk a little bit about what theories might explain that?

Christopher: I think there are a lot of ways to interpret it. I would go a little more basic than where you’re starting off. You know, we think about things that are stressful. In day-to-day ordinary language when we use the word stress, we tend to mean things that are unpleasant or things we would like to avoid. However, in scientific circles, that word has a slightly different meaning. And if you go back to the stress researcher, Hans Selye, Selye defined stress as the body’s response to changing conditions. If you think about it that way now, which I think is a much better definition and I think it’s much more meaningful, if we think about it that way, that’s neither positive nor negative. And so anything that places a demand on our body is stress. So if somebody puts their hands on our body and starts to manipulate our soft tissues, even though we may want that and even though we may perceive that as very positive– not everyone does but many of us would perceive that as very positive– it’s still on a physiological level a stressor. It is something that is impacting our body and our body is going to have to mobilize a response to. 

So it stands to reason that even something that is welcomed and that is viewed as positive is still a stress to the body a good one. But I think that’s where we should start off. It’s thinking about the fact that any change in the environment is a stressor. By the way, Selye had a formal definition for the absence of stress. Do you know what he said the total absence of stress was?

Zach: Death. 

Christopher: Death. Exactly. Right. Once the body is not responding to anything, then there’s no stress. I think that’s where I’d want to start. It makes sense that if we’re doing something to the body or we’re inviting the body to adapt to a situation, that’s going to show up physiologically as stress. But stress is not necessarily bad. In fact, stress can be very good. I attended a talk by Robert Sapolsky a couple of years ago and one of the things that he said is he said play is stress. We pursue things for fun because they are moderately stressful. We don’t seek out things that are horribly stressful, we seek out things that are moderately stressful because that is fun and engaging.

Zach: Right. Horror movies, sports, etc. 

Christopher: Yeah. And then you’ve got individual differences too. Some people really like horror movies, some people really like to drive fast, and then there’s other people who are like, “No, I don’t want that. I want less arousal than that.” So in addition to the general observation that stress can be engaging, then different individuals desire greater or lesser amounts of it. And that can be seen physiologically and then it can also be seen psychologically in the choices that people make. One of the interesting things about measuring this autonomic arousal in this way– this isn’t the research that I do directly but I’m aware of it– is it’s broadly seen that people’s response, their physiological response can be connected to the type of personality that they have– that people who are maybe pretty immune to a stress response are people who are a little more apt to get into trouble in their lives in terms of substance abuse or risky activity or criminal behavior. Now, this is a very general underlying effect. It’s not the case that you can measure someone’s physiology and say, oh, this person is going to be a criminal. It’s not like that. But if you measure hundreds or thousands of people and collate the data, you can say some general things about what kind of decisions people might make. And by the way, this extends into gambling as well. There’s some interesting research about how people make decisions in a gambling task based on how their body responds physiologically and whether their brain has normal or impeded access to what’s going on in their body. 

Zach: Yeah, we’ll talk more about that gambling study later. Isn’t one theory about psychopathic behavior personalities is that they don’t get excited/aroused in a mental way from interacting with people because they’re not wired as well to have that kind of interested response to people. So they end up looking for excitement in ways that don’t relate to other people and that kind of accounts for that. Have you ever heard that theory?

Christopher: Yes. One of the theories about antisocial personality disorder is that such people are chronically under-aroused. That they are constantly seeking to elevate their autonomic arousal because it’s chronically under aroused and their responsivity to stressors is much lower than the normal person’s would be. And going back to the polygraph thing, this illustrates one of the problems with a polygraph. If the person that you were interviewing who committed a crime has an antisocial personality disorder, and if this chronic under-arousal hypothesis is true and there’s evidence to support that, they are not going to show as much physiological arousal to lying as a normal person would because they don’t get upset by things like that. 

Zach: You’re catching the most guilty feeling people at the very best. [chuckles] 

Christopher: Yeah, potentially. At the very least, it introduces a wrinkle. At the very least.

Zach: Sure. So when the anxiety-prone people had those higher responses to massage, would you expect to see them have higher responses to pretty much anything higher than the normal population? Is that what you would expect? Or do you think there’s something specific about the massage that would make it greater than usual?

Christopher: No, I think that first you would see greater autonomic responsivity in those persons in response to any changing conditions.

Zach: Gotcha. That makes sense. Would it be possible using EDA to verify that someone was experiencing pain? Because I know there can be insurance claim cases where, you know, is someone really experiencing pain? Would it be possible to do a study on people to show, “Oh, this person is showing responses when we do this and not when we do this, and they’re actually experiencing an abnormal amount of pain.” 

Christopher: In a word, no. Pain is really interesting. There’s a great deal of increased interest in pain for some of the reasons that you just mentioned and also for others. A lot of people in the massage therapy and manual therapy and physical therapy communities and also in medicine more broadly are coming to have a greater appreciation for the psychological nature of pain. Pain is something that one experiences perceptually. And it can be caused by damage to the body, but it doesn’t have to be caused by damage to the body. So a person’s experience of pain is something that is subjective. So trying to assess it physiologically and trying to capture it with EDA or trying to make a determination that if a person doesn’t have a visible injury then how can they have pain turns out not to be a good way at all of making a determination of whether a person has pain. In fact, it’s very much the opposite. It’s very much that if a person says they’re in pain, we almost certainly ought to believe them. And while there may be some cases where a person is malingering, those cases are probably pretty rare. And we don’t want to make the mistake of accusing someone of malingering if there’s any chance that they’re not. 

Zach: Right, kind of like the legal system. You’d rather let a hundred guilty men go free than say somebody’s faking pain when you can’t be sure. 

Christopher: Yeah, I think the only way that you can really uncover whether someone’s faking something like that is to catch them doing something that they ought not be doing if they had pain. But even that’s complicated. That’s not—

Zach: Because you can work through pain. Yeah, you can force yourself to.

Christopher: Exactly. Pain is variable and pain is private. So it’s not even the same as someone who claims to have a broken leg and then a private investigator captures them walking down the street. I can’t think of any valid and reliable method for assessing someone’s pain that does not involve them reporting on their pain.

Zach: There was something in one of your studies, and maybe this was a meta-study too, but it said, “Anxious people actually had higher arousal rates when receiving massage than if they just lay down without massage. Yet they still reported feeling less anxious after the treatment.” Can you talk a little bit about that?

Christopher: Yeah. That goes back to what I was saying about the laboratory study where people– actually two different laboratory studies– where all conditions were controlled. They were all the same except for whether the person was receiving a massage or not. 

Zach: Oh, right. That was the same. Yeah, that was the same thing you were talking about. Gotcha. I just was misinterpreting when I was reading it.
Christopher: And by the way, one little detail with that is not only was everything about the setting the same, but we even had them lay in the same position and we even had them roll over at the same point in time whether they were receiving massage or not. So it turns out that not that long ago, I don’t know, 10 years ago or 15 years ago, someone published a really nice study that showed that autonomic arousal varies according to whether a person is lying prone or supine. And that’s an interesting finding. Just as a basic scientific finding, things like that are interesting. But it turns out that that even has maybe some practical applications that if we are… For example, if all the MRI research that we do involves people lying on their backs, then laying on your back is having a direct influence on a person’s autonomic arousal. And so there might be certain kinds of studies where this needs to be factored in.

Zach: Which is prone and supine? 

Christopher: Dammit, I knew you were going to ask me that. And I always have to…

Zach: Google real quick. [chuckles]

Christopher: I’m sure I’ll get it wrong. I want to say prone is face down, but…

Zach: Yeah, prone is face down, supine is face up. Yeah. That’s kind of interesting. It makes me think of people reporting that when they’re lying on their back, you get more nightmares. 

Christopher: Oh, yeah? 

Zach: Yeah, that’s what I’ve read. I think it’s due to the discomfort of lying on your back, like the fact that you have to push your body up more for the breaths or something like that. Don’t quote me on that. I’m quoting something I learned like 20 years ago, so pretty fuzzy in my memory. But…

Christopher: Well, even if we were just speculating on it, it could… Assuming it’s true, which we don’t know if it’s true or not, it’s an interesting possibility. But then that’s really interesting. People do have trends in the way they sleep, right? I can never fall asleep on my back. It’s amazing to me that people do that. 

Zach: Yes, it’s uncomfortable to me too. Yeah.

Christopher: Yeah. And that’s probably related to other things, right? That’s probably loosely connected to personality traits and it’s probably something that’s heritable because your parents positioned you as a baby to sleep certain ways, and then those things become ingrained in your habits. So there’s probably all kinds of small but interesting effects that are nested in something like that.

Zach: Yeah. I know, for me and talking to other people, sleeping on your back makes sense because you perceive it as uncomfortable that it would find its way into your dreams. And I think that it was specifically dreams about not being able to breathe and things like that. But I have to look that up now that you’ve got me interested in looking that up again. So, yeah, there was a study a couple of years ago that looked at electrodermal activity in problem gamblers versus normal population. Can you talk a little bit about that study?

Christopher: Yeah. A couple of minutes ago, we talked about the theory that people with antisocial personality disorder are chronically under-aroused. This is a similar idea. Not the same thing, and not saying that chronic gamblers are the same as antisocial personality disorder. But there’s a theory that people who develop gambling problems develop that because they don’t experience rewards in the same way, and specifically that the way their body responds to very small versus very large rewards is not as differentiated as it would be for other people. And so that study that you tipped me to and that we looked at, they tested that and they used a laboratory procedure known as the Iowa gambling task, if I remember correctly, that’s been used in lots of other studies. And they had people who were known to have problem gambling and they also had a group of normal people. And their hypothesis was confirmed that the problem gamblers showed essentially less variable reactivity. They kind of had the same response whether a reward or win was small or very large, whereas the healthier people or the normal people had a response that was more flexible that they had a greater physiological response to greater reward. So the thinking is that the problem gamblers, one of the reasons they have a harder time having adaptive behavior is that the response of their body is not in line with what’s going on in the environment.

Zach: Yeah, it was interesting. And when I put up the blog post for this episode, I’ll include links to that study. It was really interesting, especially this graph they show of the average responses on the EDA for the problem gamblers for large wins, small wins, losses, and the same for the healthy control group. Just really interesting seeing the differences in the average responses. The problem gamblers’ responses are very muted for both the losses and the wins, versus the healthy control group, the win relay spikes big and the loss has a big effect too. So yeah, it’s just really interesting seeing how that plays out with the EDA. One interesting thing I noticed, which I didn’t really see and maybe I missed it in the write up was for the healthy control group, there was a big spike on the large win. You see an immediate spike up. But for the loss for the healthy control group, there was a more gradual uplift to the EDA. And it almost made me think it takes longer to process mentally the loss or something versus the immediate jolt of the win. Yeah, it makes me just think of my own experience. You know, gambling playing poker is like whenever I’ve gotten upset about a loss, it takes me a little while to process that and I’m probably at my peak upsetness a few seconds after it happens, versus the immediate jolt of winning, you realize you win immediately and that’s exciting. Yeah, I kind of related to seeing that effect in there. 

Christopher: It makes sense. 

Zach: Yeah. These kinds of studies are interesting because I think it shows some of the problems trying to interpret these results. Because even the people who wrote this up pointed out it’s hard to draw too many conclusions from this because for one example, maybe the problem gamblers are just so desensitized from gambling higher that it’s hard to get a response from them in general. They’re used to gambling much more money so the small stakes of the study which were like $50 total just is not enough to stimulate them. So they pointed that out at the end and I thought it was just interesting. It’s kind of a similar thing with a lot of psychological research where it’s often hard to get to the underlying interpretations.

Christopher: Right. Hypothetically, we can imagine studies that would be perfectly good at getting at that. But in an ethical sense, you can’t do them. This is another thing I talk through with my students and some of them get it and then there’s probably others who think that I’m insane when I talk about this stuff. If you could take a bunch of babies and randomly assign them to different conditions and raise some as gamblers and some not as gamblers and so on, you could control for all those variables. But of course, you can’t do that. And so a piece of research like this has to work with existing groups. But then that introduces the kind of compounds that you just mentioned. I mean, when there are existing groups, these groups have different histories. And the gamblers have an extensive gambling history and so their whole way of relating to this kind of thing has been altered. And so now if you see a difference between the two groups, you can’t be certain if it was a preexisting difference or if the difference is a result of their experience, or whether it’s a combination of those things. 

Zach: Right. Because whatever makes them particular to that group changes them in some way. 

Christopher: Yeah. And it’s also funny, as you’re saying, that the rewards weren’t that large for them. I mean, you’re a poker player and I’m a poker player and so you’ve undoubtedly had this experience where you’re maybe talking about a pretty small game you were in, but you’re talking to someone who doesn’t play poker. And the amount of money that a hand was worth comes up and they’re completely shocked. They’re like, “You’re playing a hand of poker for $850?” They can’t even imagine such a thing. 

Zach: They’re like, “Okay. Well, you’re a degenerate gambler.”

Christopher: Yeah, they think you’re a maniac. [chuckles]

Zach: Right. Different worlds for sure. Yeah, I should say also– I should have lead with this– the name of that study was called, or at least the paper title was called “An Examination of Problem Gamblers Skin Conductance Responses to Large And Small Magnitude Rewards.” That was by Lisa Lole and Craig Gonsalvez if anyone wants to look that up. Also, I want to mention too, I’m sure you’ve heard that the Scientology E-meter is basically just a galvanic skin response reader, right? 

Christopher: Yeah. And that also points, you know, I was thinking about that a couple of minutes ago in case it came up. That point’s sort of one of the themes that you and I are hitting on, which is it stands to reason that they would like something like that because it’s so ambiguous. You can interpret it however you like. Yeah, that’s all it is. 

Zach: Yeah, that’s pretty interesting. That’s pretty genius of them to take something– and I don’t know if they were the first people to do that because I’ve seen other wishy-washy, pseudo, really new age crap where they’re using electrodermal activity to tell you that we’re going to give you some sort of reading about such and such, like your energy or your aura or your sensitivity to foods or something. It’s just all this nonsense, you know? I don’t know where Scientology’s use of that fits into it. That’d be interesting to kind of see the history of other wacky groups using it for those kinds of deceitful purposes. But yeah, it’s just pretty interesting. Yeah. Like you said, it’s so subjective.

Christopher: Yeah, I don’t know what their exact protocol for that is but I can just imagine that you can take it in any direction you want.

Zach: It made me think too when we were talking about the ability to use some sort of biofeedback to alter it. That really plays into it too. Because you can imagine somebody in the Scientology world being like, “Oh, well, I’ve been able to change this over time and get less response so I’m more clear. I’ve gotten rid of whatever the aliens are attached too.” It really sets it up perfectly for this ambiguous measurement that you can have some effect on over time or have different… It’ll give you different responses in different states of being or in different situations. So it’s just a great [cult tool], you know?

Zach: And I’m not saying they do this, but it’s also something that you could very easily manipulate behind the scenes if you wanted to. 

Zach: Yeah, that’s true. Yeah, I didn’t think about that aspect of it. Yeah. I’m curious, can you easily get an E-meter? I assume it’s only the higher-up people who can administer the E-meter readings. 

Christopher: I’ve seen them doing it in the field. When I used to go to the farmers market in Urbana, Illinois, there would be a table set up there and a couple of Scientologists and they would do it right there. So it’s not something that they particularly keep hidden. And the technology involved is any amateur hobbyist could assemble such a device nowadays.

Zach: That’d be a good idea. I could think about taking my own homemade E-reader into the Scientology shops and comparing the responses. [laughs] Also one really interesting thing I read about EDA was saying that it was Carl Jung who popularized it in the first place. Do you know much about that? 

Christopher: I know a little bit about that. This is a technology that’s been around for a very long time. And I say that cautiously because the way that they did it back then was much more involved than the way we do it now. People have been measuring this parameter of the body since the 1800s, but back then involved tanks of saltwater and was a pretty complicated thing to do. Whereas nowadays, you can– using a couple of medical electrodes and a device that hooks up to a computer, it’s kind of all self-contained. You can do it much more easily. But Jung was one of the people who tried out that approach in combination with word association tasks and he found it really compelling. But frankly, I think Jung is one of the most embarrassing figures in the entire history of psychology. 

Zach: [chuckles] Yeah, I’m with you there. 

Christopher: Yeah. And I want to be cautious there. We’re all products of our own time and we’re all vulnerable to getting excited about technology. So I can just imagine Jung’s time if you connected with a physiologist and that physiologist said, “Hey, I’ve got a device here that will show you alterations in the person’s nervous system in response to whatever you tell them.” I mean, that would be pretty mind-blowing and pretty exciting. So I can see why they would be extremely excited about that. 

Zach: Yeah, this actually sounds like the… From what I know of Jung, this is the most legitimate-sounding thing he was ever involved in. It was kind of more on the scientific side, and it just sounded pretty cool. The name of the book was “Studies in Word Analysis” and it was published in 1906. That was the English-translated title. And I was actually looking for it because it sounded interesting but I couldn’t find an English translation. I guess it’s rare to be able to find it.

Christopher: It probably wouldn’t be interesting. But fast forward to today, and frankly, I think a lot of us are vulnerable to modern neuroscience in a similar way to the way Jung was vulnerable to that a hundred years ago. I think there are a lot of us who are conditioned to believe that we can look into a person’s brain and by seeing what portion lights up– to use the phrase that they love to use in research descriptions– that we now have this incredible insight into how the mind works. And yes, it’s interesting and exciting and it’s going to lead to discoveries, but are we peering into the minds of people? No. There’s so much complexity involved. That’s another thing I try to get across to my students. The balance is you have to not seem too jaded and you have to not crush their enthusiasm for discoveries, but at the same time you want to get across… There’s incredible limitations to this that discovering that on average, a portion of the brain is more active in response to a certain thing is a discovery in and of itself. But that’s a long, long, long way from being able to predict someone’s behavior or knowing what they’re thinking. 

Zach: Right. And just all these unknowns about the cause versus the effect. Like, if you can see something and pattern in someone’s brain that’s different from the normal population, is the difference in the brain causing their state or their symptoms? Or is their symptoms and state causing the effect on the brain? 

Christopher: Precisely. 

Zach: A lot of unknowns there. Yeah. 

Christopher: Yeah, and that’s a really important point that a lot of people fail to understand. That at a very basic level, all of this neuroscience research– well, there’s some exceptions– but the majority of this neuroscience research is correlational research. And that’s a major shortcoming.

Zach: Also, one thing Jung said that was interesting about EDA was he allegedly said, “Aha, a looking glass into the unconscious!” about it. So right, it’s kind of interesting.

Christopher: I mean, a little bit. In a sense, it is. That’s also why people are excited about the possibility that you could get a polygraph to detect someone’s efforts to deceive. Under the right conditions with the right people, you probably can. But that’s a lot different than expecting it’s going to work under all kinds of different conditions with all kinds of different people.

Zach: Right, exactly. Yeah, knowing it works for one person is much different than saying it applies to everyone. Yeah, that’s a good point. Though the Jung stuff, the word association stuff, really got me interested in getting my own EDA detector and playing around with it with me and my wife just seeing what words and stuff would have an effect. I think you and I talked about getting one too where when we were playing poker or something. I think that’d be pretty interesting.

Christopher: Since you and I talked about that, I was thinking about what a curious poker variant it could be if everyone you were playing with had a monitor over their head that showed their EDA. And then it got me thinking like, “Okay. Well, if you did that, how would you interpret it? Would it be useful?” And I don’t know… I think you would run into the same problems that you highlight in all your material on tells. And frankly, what makes your material on tells good is that you are constantly reminding people of the importance of context. So if you were playing against somebody and they made a big bet on the river and you saw their EDA go up, is their EDA going up because they’re bluffing or because they’re value betting? Are they an experienced player or inexperienced player? Or do they even know if they’re value betting or bluffing? [crosstalk] Right, there’s even things people can do. So it’s interesting as a possibility, I don’t know what would happen. But would it be a window into their unconscious? No. 

Zach: It would make for really good television, though. They have the heart rate, the EDA, they have everything. 

Christopher: It could be really unique. Yeah. If you had a TV show like the old PokerStars Big Game, except you had them wired up to EDA, that could be pretty interesting.

Zach: Yeah, I’m surprised they haven’t done that. I had that idea years ago. I was like, “That’d make for an awesome show.” I actually think there was some show where they did that, at least the heart rate or something. There was some short-lived program production, I kind of remember seeing that. Any other things come to mind? Any interesting EDA things spring to mind?

Christopher: Oh, I don’t know about EDA, specifically. But in the lead-up to recording this with you, I’ve just been doing more thinking about autonomic response and poker. And my semester just ended. I didn’t get to play much poker during the semester but the semester ended a few days ago and so I’ve played a few sessions since then. I’ve really been trying to pay attention to my own sort of feelings of arousal as certain things came up in the game. Again, just to reiterate what you sort of report in your information about tells, is it’s just so variable. Even paying attention to that and knowing what I know about psychophysiology, I can’t discern clear relationships. If you were to ask me which is more physiologically arousing—making a big value bet with a hand that I’m sure to win or making a big bluff—intuitively, I would think that the bluff would be more physiologically arousing. But in my recent experience, thinking about it, I don’t think that’s the case. I think I experience more physiological arousal when I’m going to win a big pot.

Zach: Yeah, it’s interesting. Also, it’s just these unknowns of your state at any given time. Because I know from my experiences, some days I’m just more anxious than others. I can be anxious, like winning a big pot or something or having a big hand and betting, and then other days, I’m just for whatever reason more calm and the stuff doesn’t really affect me. It’s just a lot of unknowns. Yeah. 

Christopher: Yeah. There’s also systematic things. I’m pretty sure that my reactivity probably decreases across a session. That those first couple hands, especially if they’re momentous hands, have a big physiological effect. But if you’ve been playing for a few hours, I think the reactivity probably goes way down just because you’re doing the same thing for a while.

Zach: And also just like blood sugar level kind of effects too. Like I know, for me, not eating for a while ramps up my anxiety and things like that.

Christopher: Could be. I mean, it would just be so complicated. So when you see a study like the one we were discussing where they’re doing that, they do that under completely artificial conditions. And sometimes students get upset with that. They’re like, “Well, okay, they found this under those conditions, but those conditions are totally artificial.” And that’s like, “Well, the artificial conditions are a strength and a weakness depending on how you look at it.” You know, it’s a weakness in that this is not how gambling works in the real world. On the other hand, it’s a strength because the only way you’re going to be able to detect certain effects is if you control for all the competing explanations. So yeah, this stuff gets more complicated than people realize. And when you’re starting to deal with the intersection between physiology and psychology, it gets really complicated really fast. 

Zach: Right. It’s usually when I read about psych studies in mainstream, they get picked up by mainstream news outlets so I’m always like, “Well, they’ve really made this sound really simple. But it’s much more complex when you actually think about it.” 

Christopher: Yeah, sometimes you get simple results or clear-cut results or unambiguous results, but sometimes the inferences that are made as a result of those. I’m thinking right now about the meditation study that I did with a team of students a few years ago. This was kind of a new direction for my research but I had a student who approached me and wanted to do research on meditation, which I had never done. But I was like, “Well, okay, what I’m doing research on now has a meditative aspect to it. So I think we could probably do something.” And just to get to the point, we ended up designing… We had very few resources so there was no way we were going to be able to study hundreds of people and there was no way we were going to be able to administer hundreds of hours of training and study. So, working with the limitations we had, we said, “Okay, is there any possibility we’ll see a neurological effect if the amount of training people get is very small?” And no one had done a study exactly like that before. So we did it. Using a very small number of people in a very small amount of training, we uncovered a huge neurological difference. It was really amazing. Where these people who meditated only about seven minutes a day, in comparison to people who were not meditating– and these groups were formed by random assignment so there was no difference in the groups to begin with– the people who meditated just seven minutes a day showed this remarkable shift in their alpha wave activity from the right to the left hemisphere, which is consistent with positive mood states. So on the one hand, the finding was completely unambiguous. Meditation caused this huge shift in brain activity that we were looking for. Now, what does that mean? Does that mean that it was good for their mental health? That it made them more resilient, that it helped their focus? I mean, we don’t know that. We didn’t assess that directly. So you can have a case where the effect is crystal clear and unambiguous, but what it means or what it extends to is maybe much less clear.

Zach: So wrapping up, this has been Dr. Christopher Moyer, Ph.D. His last name is M O Y E R, if you want to search for his work online. Do you want to mention any specific ways people can get in touch with you or any upcoming projects you have now?

Christopher: The project right now is I’m at a new school here at Augustana and I’m just getting settled in. I don’t even… You know, they’ve got a blank faculty page set up for me but I haven’t even filled it in. People who want to look for my papers can find my Google Scholar page by searching for ‘Christopher Moyer massage’, that will come up. If someone would want to email me about something, [email protected]. Other than that, I don’t have a webpage or anything like that. But that’s how people can reach me.

Zach: Can people take your psychology poker course on its own or is it just part of a curriculum?

Christopher: I’m only going to be teaching it for the first time here starting in about three weeks, so we stated that as I teach that course. But more accurately, I’m about to teach that course. And it’s going to be a special topics course here at Augustana. Presently, there’s no way to take that course if you’re not an Augustana student. However, once I have the syllabus finished, I would potentially be willing to share the syllabus. But for poker players, I don’t think there’s going to be any surprises in there. I’m going to assign some things that poker players are mostly already going to be familiar with. This is a class that endeavors to get students interested in psychology by using poker as sort of a lens for psychology to get us thinking about things like you and I’ve been talking about the relationship between arousal and decision-making. But it’s also going to introduce them to things like quantitative decision-making, risk assessment, all those types of things. 

Zach: Yeah, it makes sense. That’s pretty smart. I mean, use things that people are already interested in to get them interested in deeper topics. Yeah, that makes sense. 

Christopher: Yeah, hopefully. I’m excited about it. 

Zach: Cool. Well, thanks a lot, Dr. Moyer, for coming on. I appreciate it. 

Christopher: Hey, thank you very much. I appreciate it. 

Zach: All right, bye-bye. 

This has been the People Who Read People podcast hosted by Zach Elwood. If you enjoyed it, please consider leaving a rating or review on whatever platform you listen on. It’s much appreciated. My website is