When it comes to politics, our stances may not just be a matter of opinion. They could be based in biology, too.

To find out, researcher Mike Dodd, a psychologist at the University of Nebraska, Lincoln, and his colleagues had 48 adults who were strongly conservative or strongly liberal look at a series of 33 pictures. Some were pleasant, like cute animals, while others, like maggot-infested wounds, were decidedly more cringe-inducing.

The researchers then repeated the procedure with images of polarizing politicians, including Bill Clinton and George W. Bush.

As the participants viewed the photos, scientists monitored their skin conductance, a measure of minute perspiration changes revealing how excited and emotional someone feels.

They found that, on the whole, conservatives responded more strongly to the negative images.

For example, while liberals had a stronger physiological reaction to politicians they agreed with than with those they disliked, conservatives had the opposite reaction — they responded more strongly to politicians they disagreed with, such as Clinton, than they did to the politicians they liked.

These differences are at the level of reflexes and rely on extremely basic brain processes such as attention. And while researchers can’t prove that biology influences political beliefs and not the other way around, Dodd said there’s good reason to believe that biology comes first.

“Based on your biology, you might be experiencing and processing something in a fundamentally different way from someone else,” Dodd told LiveScience.com, but added that basic brain processes certainly interact with experiences and culture to influence politics.

“What we’re showing here is that people just don’t see things the same, even if it’s the same thing,” Dodd said. “I do think there’s a nice potential here to move beyond stereotypes.”