The science behind the siren's song

There’s a lot to love about the human voice, not the least of which is its ability to attract a mate.

At certain times of the month, women’s voices are especially well suited to the task. Prior research has shown that hormonal changes during a woman’s menstrual cycle alter her voice in ways that listeners instinctively find attractive. But according to a new study co-authored by Dr. Melanie Shoup-Knox, assistant professor of psychology at JMU, a woman is in full command of her vocal charms when she is at her most fertile.

Beginning in January 2013, Shoup-Knox and her colleague, Dr. R. Nathan Pipitone of Adams State University in Colorado, enlisted 40 men and women to listen to recordings of female voices counting from one to 10. Each speaker recorded two voice samples, one at high fertility and one at low fertility.

The study found that not only did both men and women prefer the most fertile voices, but there were also changes in listeners’ physiology within a few seconds of hearing them. Galvanic skin response — a measure of electrical activity in the skin — increased by 20 percent, while heart rates jumped about 5 percent.

“So your preferences are being driven by biological changes taking place that you’re unaware of,” Shoup-Knox concludes. “It’s likely that those changes are the product of many years of human evolution. Males who pay attention to the most fertile female voices may have a reproductive advantage when choosing between potential mates, whereas females may have a competitive advantage. As a woman, if you know who’s fertile, and your boyfriend is paying attention to her, that’s important information.”

"It’s likely that the physiological changes we studied are the product of many years of human evolution." — Dr. Melanie Shoup-Knox, assistant professor of psychology

The study’s results are relevant in this age of online dating, Shoup-Knox says, in which two people may have to rely on conversation before deciding to go on a date.

For women who track their own monthly cycles, there are practical applications as well. “If a female is interviewing for a job, for example, there may be times of the month when her voice might be more appealing to the individuals who are considering her for the position.”

As a behavioral neuroscientist, Shoup-Knox looks forward to continuing the study at JMU with the help of student researchers. “We have a group here that are going to analyze the voices for any detectable differences in the harmonics of each voice from her high fertility to her low fertility phase. We would also like to do more research where we track the menstrual cycle of female listeners to see if that would affect their ability to physiologically respond to the voices.”

In addition, the voice samples themselves could be amended to say something more meaningful, Shoup-Knox says. “Instead of counting to 10, you could have the woman say something like ‘Sure, I’d like to go out on a date with you’ or ‘No, I’m sorry, I don’t want to go out with you,’ and then measure listeners’ response.”

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Jim Heffernan ('96)

Feb. 12, 2015