Who will be the next prime minister of Canada, or the next president of the United States?

According to a study by Princeton University researchers, choosing a leader can all come down to voters' quick glances of the candidates.

Voters form snap judgments ofthe competency ofa candidate based on his or her facial features, Charles Ballew and Alexander Todorov wrote in the latest issue of the periodical Proceedings of the National Academy of Sciences of the United States of America.

'The effects of appearance on voting decisions may be subtle and not easily recognized by voters.' —Princeton University researchers

Theresearchers asked test subjects to judge competency after viewing each candidate's photo. Subjects were shown the photos for three durations: 100 milliseconds, 250 milliseconds and an unlimited amount of time.

"Predictions were as accurate after a 100-ms exposure to the faces of the winner and the runner-up as exposure after 250 ms and unlimited time exposure," the duo wrote. "The findings suggest that rapid, unreflective judgments of competence from faces can affect voting decisions."

Test subjects accurately predicted about 68 per cent of the 2006 gubernatorial races in the United States, and about 72 per cent of Senate elections.

Respondents were asked to look at photos of the winners and runners-up in 89 gubernatorial races. If the subject recognized any of the candidates, their responses for that particular race were not counted, the researchers wrote.

The predictions were improved when issues such as gender and ethnicity were factored out, the report said. Of the 55 gubernatorial races where the candidates were the same gender and ethnicity, the correct predictions improved slightly to 69 per cent.

Groups of between 64 and 120 students at Princeton, in New Jersey, were used in the studies.

The researchers said their study showed that while a competent face may not be the main reason a political candidate gets elected, it is a key factor.

"Competent-looking incumbents may deter undecided voters, who have a mild preference for challengers, from voting for the challenger," they wrote.

"Our findings suggest that, in many cases, the effects of appearance on voting decisions may be subtle and not easily recognized by voters."