In his , McAleer recorded 64 people, men and women, from Glasgow, reading a paragraph that included the word “hello.” He then extracted all the hellos and got 320 participants to listen to the different voices and rate them on 10 different personality traits, such as trustworthiness, aggressiveness, confidence, dominance and warmth.

What he found was that the participants largely agreed on which voice matched which personality trait. One male voice was overwhelmingly voted the least trustworthy, “the sort of guy you’d want to avoid,” McAleer says. The pitch of the untrustworthy voice was much lower than the male deemed most trustworthy. McAleer says this is probably because a higher pitched male voice is closer to the natural pitch of a female, making the men sound less aggressive and friendlier than the lower male voices.

What makes females sound more trustworthy is whether their voices rise or fall at the end of the word, says McAleer. “Probably the trustworthy female, when she drops her voice at the end, is showing a degree of certainty and so can be trusted.”