When asked what makes a woman attractive, her voice probably isn't the first thing that most of us would list. But a woman's voice can indeed make her more seductive -- especially during the most fertile point of her cycle.
Researchers have long had a hypothesis that hormonal changes during times of peak fertility in a woman's menstrual cycle may exert a physiological effect on her vocal cords, which may in turn elicit an unconscious response from both male and female listeners. And now, thanks to a new study from James Madison University, researchers may better understand why.
The researchers played digital recordings of women, at points of high and low fertility during their menstrual cycles, for male and female subjects, who were then asked to rate the attractiveness of the voice. The researchers also tested electrical activity in the subjects' skin while they were listening to the recordings.
Both the men and the women rated the fertile voices as more attractive. For both genders, electrical activity in the skin increased by roughly 20 percent, and heart rates increased by roughly five percent.
“A man’s ability to identify and respond to a fertile woman confers him a potential reproductive advantage when choosing between potential mates,” the study's author, psychologist Dr. Melanie Shoup-Knox, told The Telegraph. “Women, on the other hand, may get a competitive advantage from detecting the fertility status of other females.”
Shoup-Knox explained that hormones can affect many types of tissue beyond the reproductive organs, which includes the larynx.
"These tissues have receptors for estrogens and progestins, which are hormones that fluctuate naturally across a woman’s menstrual cycle, as well as androgens," Shoup-Knox told the Huffington Post. "Variations in the amounts of these hormones can produce variations in the amount of blood flow, swelling, and water retention in the vocal chords, which can result in changes in vocal fluidity and hoarseness. These physical changes are similar to the effects of the same hormones on cervical tissue. Because of these changes in the voice across the menstrual cycle, many professional vocalists choose to use hormonal birth control to eliminate inconsistencies in vocal performance."
When it comes to men, on the other hand, research has found that women overwhelmingly display a preference for deeper voices. "Low-frequency harmonics were judged as being more attractive, older and heavier, more likely to have a hairy chest and of a more muscular body type," the authors of a 2000 study on the topic wrote.
The findings were published in the journal Physiology and Behavior.