Here's a fun trick: scare someone you don't know, then guess whether they favor the death penalty and the war in Iraq based on how freaked out they got.

People with stronger startle reactions are more likely to support ideologies associated with conservative American politics, including the Patriot Act, obedience and biblical truth — and less likely to favor gun control, foreign aid, abortion rights, gay marriage and pornography, according to research published in today's Science. Those who are slower to scare are more likely to harbor traditionally liberal politics.

The findings build on previous research showing that experiencing trauma can skew one's politics to the right.

But what comes first: biology or politics? "It could be working either way," says study author John Alford, an associate professor of political science at Rice University.

Your visceral reactions to situations could encourage your political leanings, or your ideology could shape how you respond to circumstances, his study notes. "This could be a fairly durable but still learned response, or a difference in underlying physiological systems themselves," Alford says.

The results are based on surveys of 46 Nebraskans who said either that they strongly identified with policies that protect the social order or with ideologies that do not. Scientists then measured how strong they blinked and how easily their skin conducted electricity when they looked at threatening, non-threatening and neutral images.

Having conservative leanings predicted stronger physiological reactions to the scary pictures, including a spider sitting on a person's face, a bloodied face and a maggot-infested wound. People who leaned more politically left didn’t respond any differently to those images than they did to pictures of a bowl of fruit, a rabbit or a happy child.

Political ads, then, are most likely to reinforce what we already believe than to change our minds. "If the content is not there, you may not alter their position at all," Alford says of campaign spots. "They're more likely to rally the troops and get the base to turn out than to persuade anybody."

(iStockphoto/Claudia Dewald)