In early 2008, while Barack Obama and Hillary Clinton were seeking the Democratic presidential nomination, 85 college students participated in an experiment.
They looked at a person's written endorsement of Clinton, then answered questions about whether the endorser's position was surprising, and whether the endorser was likable, competent, persuasive and annoying.
One group of students read an endorsement with a photograph of a nice-looking white woman in her early 40s. The other group read the same endorsement with a photo of a pleasant-looking white man of similar age.
The results? The female students rated the male endorser as more competent and less annoying than the female endorser, and were more likely to agree with his opinion.
Meanwhile, the male students rated the male endorser as less competent and more annoying than the female one.
What's going on here?
Research suggests that by rating the women endorser lower, the female students were distancing themselves from Clinton, a candidate who, in some people's eyes, came across as cold and unfriendly. The students also may have transferred those negative impressions of Clinton to the women endorser.
And the male students may have rated the male endorser negatively because he was endorsing a female candidate, and thus a traitor to the idea that men should stick together.
Those are a few of several possible explanations from the world of social psychology, the study of how people's thoughts and behavior are influenced by their social context.
Alex Czopp, an associate professor of psychology at Western Washington University, oversaw the experiment while he teaching at the University of Toledo, in Ohio.
With political campaigns at fever pitch, Czopp will teach a public course on "Persuasion and Social Influence," about how the media, government, companies, family members and friends try to influence what people think and do.
If you think about how people make decisions, the golden end of the spectrum is when they gather and study facts and then use logic to decide. People are more likely to do that if they have the time, information and the motivation, such as when they choose a college or pick a computer.
"We like to think this is how we all make a lot of decisions," Czopp said.
Yet people often lack the time, information and impetus needed for well-researched decisions. Instead, they listen to friends and other people they trust, and go with their gut feelings: Is the source a man or a woman? Is the candidate handsome? Does the person seem likable?
Campaign ads play to those gut-level influences when they present warm, nostalgic and iconic images - the hard-working factory laborer, the farmer in a field - and present people from your own state, party or group who favor a candidate or issue.
Negative campaign ads also play to the emotions with edgy soundtracks, a staccato mix of black-and-white and frozen images, and unflattering photographs of the opposition.
How can voters make sense of it all? To start, Czopp said they should recognize the tools of persuaders, and balance the information they see, hear and read against any biases of the source.
And because people tend seek out information that supports their views - it's called "confirmation bias" - it doesn't hurt to broaden your mix of news sources.
Finally, people should ask themselves if they're satisfied with the basis for their vote. Are they well-informed? Have they put time and effort into it? Have their given the candidates a fair shake?
"We want instant gratification, instant knowledge," Czopp said. "People don't question, 'Why do I like this person?'"
What: "Persuasion and Social Influence," a public course taught by Alex Czopp.
When: 10:30 a.m. to 12:30 p.m. four Saturdays: Oct. 13 and 20, and Nov. 3 and 10.
Where: Library presentation room, Western Washington University.
Cost: $73 general, $58 for members of the Academy for Lifelong Learning.
Registration: Deadline is Oct. 6. Call 360-650-4970 or see wwu.edu/all.
Reach DEAN KAHN at email@example.com or call 715-2291.