Michael Dodd, a professor at the University of Nebraska, wanted to find out if people who consider themselves left-leaning have physiological differences from those who are right-leaning.

In his two recent studies, which were covered by The Economist, he tested 46 liberal and conservative Nebraskans by showing them 33 different, emotionally charged images. He then measured involuntary physiological responses like skin conductivity and eye movement. Some of the pictures showed images associated with negative emotions: a spider on a man’s face, a man being beaten by a mob, etc. Other pictures showed more positive images, like a smiling child or a small rabbit.

As one would expect, the negative pictures drew more of a physiological reaction from conservative subjects, and the positive pictures drew more of a reaction from liberal subjects. The more partisan the subject, the stronger the correlation.

This research, as Dr. Dodd points out, does not support any conclusions about whether liberalism or conservatism is based within DNA. It merely suggests that humans tend to respond physiologically to either negative or positive emotional stimuli, and that correlates strongly to political affiliation.

Our political system was conceived from the era of Enlightenment, when man took for granted that he could be the agent of reason alone. Our Founding Fathers worshiped at the alter of the Free Exchange of Ideas, believing that such freedom would result in the best ideas winning a well-reasoned argument. And yet there was, even in them, an irrational tendency towards either the avoidance of the fearful or the embrace of optimism that predetermined the side they would take in these arguments of supposed pure reason.

Over a year ago, I wrote a post called The Secret Triggers Behind the American Identity, where I talked about the nature of Tea Party populism. It’s rarer to see populist movements come from the right as opposed to the left, and so the Tea Party Angst makes an interesting study.

American history shows a unique connection between religion, existential angst, and wealth-building. This comes from the process of settling and cultivating hostile terrain. Many of the original American colonists were already a persecuted minority when they arrived here. They came to prosper and spread their unique rendition of the Word of God.

In hostile conditions, among hostile natives, Protestant colonists and settlers depended on guns and religion as a matter of survival (and eventual prosperity). And so the perspective of the ancestors of present-day conservatives is one of a huddled circle of outward-pointing rifles, staring into the darkness as the eyes of the wilderness stare back.

Our Manifest Destiny past might explain a unique physiological reaction to fear, but Dr. Dodd’s research adds something new: a disposition for left-leaning subjects to show a physiological response to images of endearment and optimism. That disposition is without historical or cultural explanation. It may indeed be that humans are naturally predisposed either to one side or the other.

It’s worth noting that this might be why political debates and discussions do not generally tend to convert people to the other side of the argument. Political agreement and persuasion may have very little to do with reason. This is ironic, because we consider ourselves to be intelligent and reasoning creatures.

Related articles

• Human Nature and the Neurobiology of Conflict (wired.com)
• Biology of politics: Liberals roll with the good, conservatives confront the bad (scienceblog.com)