Want to know if your partner's cheating on you? Just listen to their voice
Picture Morgan Freeman, Donald Trump or Margaret Thatcher. Most likely you can hear their voices in your mind, and the characteristic inflections that they put on certain words, as well as their tone and pitch. Even without listening to the words, when you hear someone speak you can pick up important information about them from characteristics such as how loud or deep their voice is.
At the most basic level, voices convey biological characteristics such as whether someone is male or female, their body size and physical strength, age and sexual maturity. For example, Donald Trump's voice can signal to you that he is a man, and that he has passed middle age. But did you know that voices can also signal a person's attractiveness, fertility and even the likelihood of them being unfaithful?
A popular theory with evolutionary psychologists, known as "cads versus dads", suggests that more masculine, dominant men are not as paternal and generally invest less in their children and grandchildren than less masculine men. Yet research shows women generally prefer deeper voiced, more masculine-sounding men, especially when these women are near ovulation.
This may be because partnering with deeper-voiced men could lead to genetically healthier children. Deeper voices have been linked to having more surviving children and grandchildren, higher testosterone and lower stress hormones, and longer-term survival in men.
On the other hand, deeper-voiced men are also rated by women as more likely to cheat on a partner and as less trustworthy in general. Women who judge men with lower-pitched voices as more likely to cheat also prefer those men for short-term rather than long-term partners. Meanwhile, when women are breastfeeding and so currently taking care of a child, they are more likely to prefer men with higher-pitched voices than at other times.
This suggests women use something in men's voices to try to assess how likely to cheat they are, as well as their general trustworthiness. This in turn can affect their attractiveness as a partner, depending on whether the women are drawn towards the paternal care of a potential long-term mate or just good genes.
Spotting a cheater
But can our voices really indicate whether we are likely to cheat? A recent study suggests that they can. Participants were played recordings of people speaking and given no other background information about them, and successfully rated cheaters as "more likely to cheat" than non-cheaters. Interestingly, women were better at this task than men.
The recordings were taken from people with voices of similar pitch and attractiveness, who were of similar size and shape, and had similar sexual histories (aside from cheating). This means that none of these factors affected the results. So we currently don't know what cues the participants used to judge whether the voices came from cheaters.
It is not only women who can pick up on men's vocal cues of good genes and likelihood to cheat, and use it to their benefit. A woman's voice changes during her menstrual cycle when she is not using contraceptive pills. Perhaps unsurprisingly, men find women's voices most attractive when the women are near ovulation (most fertile), than at other times of the month. This information is important to pick up on, as women do not display very explicit signals that they are fertile (unlike baboon females whose bottoms turn red, or female deer who release scents to advertise their fertility).
Voices can also signal whether someone is interested in you. In one clever study, participants were asked to judge the voices of individuals who spoke in a different language to attractive or unattractive potential partners or competitors.
The researchers found that, when talking to attractive people, men's voices tend to reach a deeper pitch, and both men and women increase how varied their pitch is so their voices sound more dynamic than monotonous. Practically speaking, picking up on these types of cues could allow someone to decide whether a person they are talking to might be attracted to them or not.
In these ways, the non-verbal characteristics of voices can play a significant role in signalling health, fertility, attraction and potential infidelity, to name a few. Picking up on these cues, alongside the many other cues we receive when talking to someone, can help us make more informed and well-rounded choices about who to spend time with and who to avoid. But the next time you find yourself listening to and judging someone's voice for these subtle cues, remember that they are judging yours, too.