When choosing a partner, women believe the lower the man's voice, the more likely he's going to cheat. Conversely, men think a woman with a higher voice is more likely to be unfaithful, researchers have found.

The study, published in the latest edition of the online journal Evolutionary Psychology is the first to examine the link between voice pitch and perceived infidelity and offers insight into the evolution of the human voice and how we choose our mates.

"In terms of sexual strategy, we found that men and women will use voice pitch as a warning sign of future betrayal. So the more attractive the voice—a higher pitch for women and lower pitch for men—the more likely the chances he or she will cheat," says Jillian O'Connor, a graduate student in the Department of Psychology, Neuroscience & Behaviour at McMaster University and lead author of the study.

"Infidelity is costly with the emotional impact, financial costs and potential loss of the family unit. But this suggests that through the evolutionary process, we have learned ways to avoid partners who may be unfaithful as a protection mechanism," she says.

Participants in the study were asked to listen to two versions of recorded clips from a male voice and a female voice, which were electronically manipulated to be both higher and lower in pitch. They were then asked which one, from each pair, was more likely to cheat sexually on their romantic partner.

"The reason voice pitch influences perceptions of cheating is likely due to the relationship between pitch, hormones and infidelity," explains David Feinberg, an assistant professor in the Department of Psychology, Neuroscience & Behaviour and advisor on the study. "Men with higher testosterone levels have lower pitched voices, and women with higher estrogen levels have higher pitched voices. High levels of these hormones are associated with adulterous behaviour and our findings indicate individuals are somewhat aware of the link and may use this in their search for a romantic partner."