Kevin B. Smith, Ph.D.

Kevin B. Smith Ph.D.


Politics Makes Me Sweat

Conservatives sweat the scary stuff – liberals just don’t.

Posted Nov 14, 2013

An obvious reason for all this interest is the organ where sweat happens: the skin. Neuroscience might be the glamour field for investigating the biological basis of social attitudes and behavior but skin is also a sensory and processing organ, and a big one at that. Of the 78 organs in the human body, skin is by far the largest, accounting for 20 to 25 pounds of a person’s total body weight. By way of comparison, a typical brain weighs in at a comparative paltry 3 pounds or so. Importantly, skin is not just a prophylactic barrier to keep germs out of your body, nor is it just a nice soft sheath that wraps you in a socially presentable package. It is also an information processing organ that is responsive to a variety of signals originating within and outside our bodies. Those signals can be picked up by measuring changes in the electrical properties of skin, which have long been known to fluctuate based on internal psychological states (these fluctuations are generically known as electrodermal activity, or EDA). This is why EDA has been a central part of polygraph (lie detector) protocols for decades. Moreover, compared to electrical activity in the brain, measuring the skin’s electrical properties is easy, cheap and can be done with an extremely high degree of accuracy.

True, this accuracy has not provided a foolproof way to figure out if a given individual is speaking gospel or telling tall tales. Polygraphs, after all, can be beaten by the guilty and damn an innocent as a liar. Yet there is no doubt that EDA can tell us something important about general patterns of (autonomic) nervous system activity. We know this because, unlike some of the mysterious processes of the brain, scientists have a pretty good grasp on what makes us sweat. Sweating is the result of the skin responding to signals coming from the sympathetic nervous system (SNS), the part of nervous system that quickly and without conscious input    prepares the body for action. Part of this preparation entails opening sweat glands. When the SNS activates these glands, moisture is drawn to the surface of the skin, sort of like racks of teeny straws sucking up fluid.  A hot room or the thought of a hot date can both induce sweat, but only the former involves ambient temperature. The latter is an example of the SNS responding to an internal psychological rather than an external environmental state. It is responses to those internal signals that most interest us, and we can investigate the topic pretty effectively because one type of sweat gland, the eccrine gland, is particularly sensitive to SNS signals generated by internal psychological states. Eccrine glands are densely concentrated in the palms of our hands, and the key thing to remember is that when the SNS perks up because of an internal psychological state like fear or arousal, thousands of those little straws in and around our palms start sucking moisture toward the surface of the skin.

Bunny Rabbit

Non-threatening Image


Threatening Image

At this point you might be thinking thanks for reminding me to get some anti-perspirant, but what does this have to do with your politics?  Well, if political orientations are biologically based, stable individual-level differences in SNS activation seem like good place to look for them, and indeed a number of studies have found that SNS activation correlates with particular sets of political attitudes and behaviors. One of these studies was conducted by our lab back in 2008. We brought in about 50 adults and showed them several images on a computer screen—everything from babies and cute bunnies to animals of a more threatening nature. We were interested in the individual level differences in EDA response to threatening versus non-threatening images. What we found was that the pattern of EDA response to these images was systematically correlated with a particular set of policy positions. We termed these “socially protective policies” because that is exactly what they seemed to reflect: policies designed to protect the interest of the participant as well as the participant’s social group from threats. These issues included the death penalty, immigration, foreign aid, and gun control.

Graph of Results

Liberal vs. Conservative EDA Response to Threatening Images


Adapted from Predisposed: Liberals, Conservatives, and the Biology of Political Differences, Routledge Books, Sept 2013.