A woman鈥檚 voice becomes more attractive when she is most fertile. That鈥檚 according to Nathan Pipitone and Gordon Gallup of the State University of New York at Albany.
The pair recorded women counting from 1 to 10 at four occasions during their menstrual cycle. They then replayed the recordings at random to male and female students and asked them to rate the attractiveness of the voices. Both males and females judged the women鈥檚 voices to be most attractive if they were recorded during the peak fertility period of the menstrual cycle, and less attractive if they were recorded during non-fertile periods (Evolution and Human Behavior, ).
The results are in line with evidence that the female voice box, or larynx, is under the influence of sex hormones, says Gallup. He says the changes in the female voice during peak fertility support the view that women are 鈥渄ifferent鈥� at that point in the menstrual cycle 鈥� in other words, that they experience oestrus.
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鈥淐hanges in the attractiveness of a woman鈥檚 voice during peak fertility support the view that women experience oestrus鈥�
The theory of human oestrus remains controversial because its effects are subtle; human females show none of the distinct genital swellings seen in other female mammals 鈥渋n heat鈥�. But there is increasing evidence of more subtle changes. 鈥淥ther differences include changes in sexual receptivity and odour sensitivity,鈥� Gallup says.
Martie Haselton and Greg Bryant at the University of California, Los Angeles, say that vocal pitch plays an important role in judging fertility. 鈥淲e have found that voices are higher in pitch on high-fertility days of the cycle,鈥� says Haselton.
The fact that men notice the differences in vocal attractiveness suggests that there is a subtle evolutionary battle of the sexes going on, says Gallup: as women evolve ever more efficient ways to conceal fertility 鈥� to avoid unwanted attention 鈥� men become increasingly sensitive to the tiny changes that do occur. Other women also pick up on the changes, perhaps to keep an eye on the competition, he suggests.
Geoffrey Miller at the University of New Mexico, Albuquerque, showed last year that women lap dancers earn more tips during their fertile days. 鈥淭he voice changes might explain some of the shift in lap dancer tip earnings,鈥� he says. 鈥淒ancers certainly chat with their customers.鈥� But Miller points out that there is also evidence that visual attractiveness changes during the menstrual cycle. 鈥淰oice quality is unlikely to be the whole story,鈥� he says.
