Fierce individualists, Americans figure that we choose our own political beliefs, but actually it could come down to biology.

Individuals who are more easily startled by threats are more likely than others to support protective policies, such as military spending, the Iraq War and the death penalty, finds a new study.

Researchers over the years have put forth several factors to explain a person's political beliefs, including religion, culture, genetics and everyday experiences.

While the new study involved a relatively small number of participants and doesn't topple any of these ideas, it adds physiology as another driver of political leanings. It suggests, at least for those with strong political views, that some people are somehow built differently than others, either through genetics or life experiences or both.

Stress and politics

The study involved 46 Nebraska residents, chosen for having strong political beliefs from a larger population of randomly selected individuals. The participants answered survey questions on political beliefs, personality traits and demographics.

A couple of months later, the same participants underwent tests for their so-called startle reflexes. The researchers measured levels of skin moisture as indicators of stress and anxiety for each participant as he or she looked at threatening images, including a large spider on the face of a frightened person, a dazed individual with a bloody face, and an open wound with maggots in it. Similarly, participants also viewed three non-threatening images (a bunny, a bowl of fruit and a happy child) placed within a series of other images.

The researchers also measured the intensity of the participants' eye blinks in response to sudden, jarring noises. Harder blinks are linked with a heightened state of fear, the researchers say.

Participants who scored high on the skin and blinking stress tests also tended to support military spending, warrantless searches, death penalty, the Patriot Act, obedience, patriotism, the Iraq War, school prayer and the concept of Biblical truth. And they tended to oppose pacifism, immigration, gun control, foreign aid, compromise, premarital sex, gay marriage, abortion rights and pornography.

Those who were less startled by threatening images and noises were more likely to favor foreign aid, liberal immigration policies, pacifism and gun control.

The researchers found no significant differences in the stress tests of participants when viewing the non-threatening images.

They also didn't find any real difference between men and women regarding their jumpy responses, though females did tend to be a little less supportive of defense spending and more supportive of pacifism, said researcher John Hibbing, a political scientist at the University of Nebraska-Lincoln.

Unyielding political beliefs

The results, if supported by further research could have implications for the everyday hair-pulling discussions about politics, Hibbing said. Often, he said, individuals with strong, opposing views will become frazzled over why the other person can't "see the light."

"But if I realize that maybe you do experience the world somewhat differently than I do and you see threats where I don't or vice versa and you just feel it differently, that might increase our tolerance a little better," Hibbing told LiveScience.

He added, "It might make it a little easier to appreciate why political disputes are so difficult to get around. They're almost ubiquitous."

The results might also help to explain the seemingly unyielding beliefs of some individuals with strong political views. "There are a lot of people with strong political beliefs and they just won't change. They build the world around their existing beliefs," Hibbing said. "And we're trying to figure out where those existing beliefs came from."

The research, which will be detailed in the Sept. 19 issue of the journal Science, was financially supported by the National Science Foundation, ManTech Corporation, and University of Nebraska-Lincoln.