Study examines link between political differences and humans' built-in physiological traits

Conservatives, gay marriage opponents registered strong reactions to disgusting pictures

Most likely, you would be disgusted if confronted with a picture of a man eating a mouthful of writhing worms. Or a particularly bloody wound. Or a horribly emaciated but still living body. But just how much disgust you feel may lend important insight into your personal political proclivities.

In a new study, political scientists closely measured people's physiological reactions as they looked at a series of pleasant and unpleasant images. Participants who identified themselves as conservative -- and, in particular, those who said they were against gay marriage -- had strong physiological reactions when shown the gross pictures.

The study, the latest to examine the connection between political differences and humans' built-in physiological traits, was co-authored by University of Nebraska-Lincoln political science professors Kevin Smith and John Hibbing and was published this month in the Public Library of Science One.

"This is one more piece of evidence that we, quite literally, have gut feelings about politics," Smith said. "Our political attitudes and behaviors are reflected in our biology."

Researchers worked with 27 women and 23 men who were chosen from a larger pool of participants who also underwent thorough political questioning. The subjects were shown a series of disgusting and also relatively pleasant images while electrodes on their skin measured subtle skin conductance changes, which indicated an emotional response.

As predicted, conservatives responded to the pictures with much more intense disgust than did liberals. Attitudes in opposition to same-sex marriage were highly connected.

The results add to a growing area of research that suggests biology plays a larger role in influencing political orientation than many might think. Recent UNL work has produced findings in this area, including a 2008 study that found people who are highly responsive to threatening images were likely to support defense spending, capital punishment, patriotism and the Iraq War.

"The proper interpretation of the findings (in the current study) is not that biology causes politics or that politics causes biology," the authors write, "but that certain political orientations at some unspecified point become housed in our biology, with meaningful political consequences."

Acceptance of the role of involuntary physiological responses is not easy for many, however: "Most are proud of their political orientations, believe them to be rational responses to the world around them, and are reluctant to concede that subconscious predispositions play any role in shaping them," they write.

Still, the authors suggest that if recognition of the relevance of politics of involuntary physiology became more widespread, it could diminish frustration from the perceived illogical inflexibility of political opponents and reduce political hostility.

"After all, if political differences are traceable in part to the fact that people vary in the way they physically experience the world, certitude that any particular worldview is 'correct' may abate, lessening the hubris that fuels political conflict."