Candidates with lower-pitched voices may get more votes in the 2012 election.

A new study by biologists and a political scientist shows that both men and women prefer political candidates with deeper voices. The results also suggest that biology — not just partisanship or ideology — can shape voters’ choices.

“We often make snap judgments about candidates without full knowledge of their policies or positions. These findings might help explain why,” said Duke University biologist Rindy Anderson.

“It’s clear that our voices carry more information than the words we speak. Knowing this can help us understand the factors that influence our social interactions and possibly why there are fewer women elected to high-level political positions,” she said.

To test voters’ preference on voice pitch, Anderson, Duke biologist Susan Peters and University of Miami political scientist Casey Klofstad recorded men and women saying, “I urge you to vote for me this November.” The scientists then edited each recording to create a higher- and lower-pitched version of the original.

The team played the recordings of the female voices to 37 men and 46 women at the University of Miami, and the male voices to 49 men and 40 women at Duke. They found that both men and women “elected” the candidates with the lower-pitched voices, regardless of the speaker’s gender. The results appear in the March 14 Proceedings of the Royal Society B.

This research is an “interesting first step toward understanding the psychological mechanisms that affect voters’ choices,” said Brad Verhulst, a researcher at Virginia Commonwealth University in Richmond. He was not involved in the study, but says the experiment is an “exciting application” of previous work on the way visual cues affect people’s perceptions of candidates and their competence.

Voice pitch can also affect how people perceive a speaker’s competence, honesty and strength, according to past research. But no one had applied that connection to voters’ preferences for the voices of both male and female candidates, Anderson said.

In a second experiment, Anderson and her colleagues played the same recordings to three groups of 35 men and 35 women and asked the subjects to select which candidate seemed stronger and more trustworthy and competent.

Both men and women tended to perceive lower-pitched female voices to have all three traits. But only male subjects perceived lower-pitched male voices to be stronger and more competent. They may have been tuned into pitch to gauge the speaker’s competitiveness and social aggressiveness, Anderson said.

Women, however, may not discriminate strength and competence in male voices because they are tuning into different cues, vocal or otherwise, to evaluate those traits, she said.

But the findings are based on hypothetical elections conducted in the lab, she said.

“We need to be very careful about interpreting these results in a broader context,” Anderson said. The findings raise the possibility that, since women tend to have higher-pitched voices than men, their voice could be one of many different factors that influence gender inequality in leadership roles, she said.

This was a carefully controlled study, Verhulst said. But “until the idea is more thoroughly fleshed out, the broader application to real-world politics is still a conjecture,” he said.

As a result, Anderson said she and her collaborators plan to test what they have learned in the laboratory in the 2012 elections.