Hey, candidates. Want to win an election? Simple. Just appear competent—even if you're not. A new report confirms what may be some politically inclined people's worst nightmare: looks matter.

Princeton University researchers asked student volunteers which of two candidates in gubernatorial races appeared more competent. Much to the scientists' surprise, their picks turned out to be the voters' choices.

Study participants were shown photos of the winners and losers in 89 political races that took place between 1996 and 2002. The subjects were given either 100 milliseconds, 250 milliseconds or an unlimited amount of time to choose candidate that they perceived as more competent; in all cases they were instructed to go with their gut. The students' selections were also the election winners in 64 percent of the cases.

In a second trial, the volunteers were given either 250 milliseconds or two seconds to mull over their decisions. When given longer time to ponder, the students' individual responses became 5 to 7 percent less predictive, but their overall success rate bumped up to an average 69.1 percent. In a third experiment, which involved yet-to-be-held gubernatorial races, the group did similarly well (68.6 percent) when asked to go with their first impulse, but take as much time as they needed to answer, allowing them to deliberate.

"All of the action goes on in the first 250 milliseconds of exposure, and then there's not much going on," says Alexander Todorov, an assistant professor of psychology and co-author of the study, which appeared in Proceedings of National Academy of Sciences USA, noting that these 250-millisecond trials yielded the greatest predictive success. "If they deliberate, they get slightly worse. [Though], they are still above chance in picking the winner."

Moshe Bar, principal investigator of Harvard Medical School's Visual Neurocognition Lab, says that extremely fast impressions are often more relevant to judgments that affect survival, such as whether something we are looking at poses a threat. "I think there is a repertoire of characteristics that could be inferred from facial features," he says. Although not critical to survival, we often make predictions—for example about a person's intelligence and ability to govern from the appearance of their face. "Just to protect ourselves, we often stick to these first impressions," he continues. "We tend to err on not changing our mind too quickly and then realizing that our first impression [was] correct."