WASHINGTON Estrogen fuels feelings of power and competition in women in much the same way testosterone does in men, researchers said on Wednesday in a study that shows the need to win is every bit as feminine as it is masculine.
Estrogen levels shot up in power-motivated women when they won and plummeted when they lost, while the opposite was true in women who appeared not to be interested in power, the researchers found.
"The biology of dominance in women has been vastly under- researched. On top of that, it sets up very nice parallels with men and testosterone," said Steven Stanton of the University of Michigan, who conducted the study.
Earlier this month, British researchers reported that male financial traders made more money when their testosterone levels were high.
Stanton, working under the guidance of German researcher Oliver Schultheiss of Friedrich-Alexander University in Erlangen, wanted to see if estrogen or testosterone was affected when women competed.
"We put women in this study in a face-to-face contest where they competed on a computer task for 10 rounds," Stanton said in a telephone interview.
"Following each round, they were told whether they won or lost and they could watch each other's reaction to winning or losing."
Saliva samples were taken to measure their hormone levels.
"Even before the contest started, we have this measure of power motivation or dominance motivation that we use," he added.
Volunteers are shown a neutral picture and asked to write a short story about it. "We look for themes that are related to power. The more power themes that someone writes about, the more power-motivated that we consider them," said Stanton.
Estrogen was linked to personality type as well, Stanton said -- and the women, mostly in their 20s, were evenly divided.
"The higher the women were in estrogen, they higher they were in this measure of power motivation," he said.
"To sum up, we have found that estradiol (estrogen), but not testosterone, and a nonconscious need for dominance are positively related in women. This positive relationship is strongest in single women (and) women not taking oral contraceptives," they wrote in the journal Hormones and Behavior.
Women who seemed to have less of a need to dominate were affected differently, Stanton said.
"It was almost a flip-flop of the result. Those who were not power-motivated, if they won, their estrogen went down. If they lost, their estrogen went up a little bit," he said.
"Estrogen is very behaviorally potent and is actually a close hormonal relative to testosterone. In female mammals, estrogen has been tied to dominance, but there has been scant research examining the behavioral roles of estrogen in women," added Stanton.
He hopes also to test women past menopause, whose bodies produce less estrogen, and also to test men and women as they compete against one another.
(Editing by Sandra Maler)