During ovulatory cycle, women tend to become ambitious and nurture the urge to outshine other women, says a study.
"We found that ovulating women were much less willing to share when the other person was another woman. They became meaner to other women," said Kristina Durante, assistant professor of marketing at the University of Texas at San Antonio (UTSA) College of Business and lead study author.
Researchers also found that for around one week every month, there are also changes in women's economic behaviour.
As part of the study, researchers made the two categories of women play the "dictator game", where a fixed amount of money is given to a person and it is on her as to with whom she wants to share the money.
Non-ovulating women shared about 50 per cent of the money with another woman and for ovulating women the share was only half as much. They preferred to keep the money for themselves.
In another experiment, women were given two choices. In the first option, if the woman owned a $25,000 car, other women would get $40,000 cars. In the second option, if the woman got a $20,000 car, the other women would own $12,000 cars. Ovulating women went for the second option as this gave them a 'higher social standing' compared to the others.
"What's interesting about this finding is that ovulating women are so concerned about their relative position that they are willing to take less for themselves just so that they could outdo other women," said study co-author Vladas Griskevicius, associate professor of marketing at the University of Minnesota's Carlson School of Management.
Researchers say that during ovulation, women were nicer to men, compared to women and this could be a way to flirt with men.
The study, published in Journal of Marketing Research, could set a new path of study in consumer behaviour and marketing.