Hormones associated with the menstrual cycle appear to drive sexual attraction more than we know.
By Bridget Murray Law
March 2011, Vol 42, No. 3
Print version: page 44
Most animals aren’t shy about showing their interest in mating. The male frigate bird puffs out his throat into a gigantic red balloon. Female cats yowl and spray urine during estrus, their time of ovulation and sexual receptivity. And in female chimps, estrus swellings of the external sex organs can get as large as a cantaloupe — not something a male could easily miss.
In humans, signs of sexual interest aren’t nearly so obvious. The male of the species generally doesn’t broadcast his constant readiness for sex, and during her window of fertility at ovulation, the female doesn’t display any outward signs. Some biologists and anthropologists have theorized that this “loss of estrus” in people makes us less driven by sex hormones than other animals.
But according to a steady stream of new studies by evolutionary and biological psychologists, that may not be the case. This research indicates that the hormonal changes of a woman’s monthly cycle may be more powerful than we’ve ever conceived — compelling women to advertise when they’re ovulating, and men to notice. Although women aren’t showing off swellings, yowling or spraying, studies suggest they may dress more provocatively, flirt more, and possibly become more sexually excitable, for roughly six days mid-cycle, before and after ovulation. They even show minuscule shifts in voice pitch, scent and skin tone, some studies suggest.
These changes are not lost on men, whose own hormones and mating behavior respond to a woman’s cues, as well as how the woman treats them, says Jon Maner, PhD, a hormones researcher and associate professor of psychology at Florida State University. To illustrate: In one of his studies, men actually inched closer to a woman — and mimicked her gestures more — when she was ovulating.
There are, of course, critics of this line of research, who believe that it’s overly focused on ovulation-related behavior, and that it doesn’t necessarily translate into what happens in real-world relationships. “These lab studies have never, to my knowledge, been extended into actual partner choice,” says hormones researcher Sari van Anders, PhD, an assistant professor of psychology and women’s studies at the University of Michigan, Ann Arbor. “If ovulation affects real-life mate choice so strongly outside the lab, why haven’t we seen these results?”
There is also research to suggest that women aren’t the only ones with hormonal cycles that affect behavior: Men’s testosterone appears to cycle throughout the day, month, and possibly even the seasons, affecting their moods and sexual desire. Also, drops in testosterone with age may trigger something of a male menopause, or “andropause.” Yet another source of debate is the degree to which hormones may respond to people’s sexual behavior, versus directly influencing it.
This much, however, is not debatable: Both men and women have little to no awareness of just how much these hormonal machinations in their bodies affect what they do.
“The vast majority of all this occurs outside of our conscious awareness,” says Maner. “It’s kind of like chemistry between two people. You know when you have it, but you’re not sure what it is.”