New York: Don't know why she is in love with you on some days while avoids coming close when you need her the most?
Ovulating women have evolved to prefer mates who display sexy traits - such as a masculine body type and facial features, dominant behaviour and certain scents, says fascinating research.
Desires for those masculine characteristics do not last all month - just the few days in a woman's cycle when she is most likely to pass on genes that might have increased the odds of her offspring surviving and reproducing.
"Women sometimes get a bad rap for being fickle but the changes they experience are not arbitrary,” said Martie Haselton, a professor of psychology at University of California, Los Angeles (UCLA).
"Women experience intricately patterned preference shifts even though they might not serve any function in the present."
Haselton and Kelly Gildersleeve, a UCLA doctoral candidate in psychology, spent three years attempting to resolve the mystery.
They solicited raw data from dozens of scholars who have conducted research on the topic and then translated the data from 50 studies into the same mathematical format so that the findings could be statistically analysed together.
The findings are less clear, however, about which male characteristics are most alluring to ovulating women.
But women's responses to male body scents could be capable of producing the strongest effects, Haselton said.
"If women notice suddenly that they're attracted to the guy in the next cubicle at work, it does not necessarily mean that they do not have a great long-term partner, they are just experiencing a fleeting echo from the past,” explained Haselton.
The findings were published in the journal Psychological Bulletin.