Menstrual cycle can affect prejudice

A woman's menstrual cycle can have an effect on her bias against male strangers. This is according to new research from Michigan State University, which found that a female's attitude against a male is stronger when she is fertile.

Published in the online research journal Psychological Science and funded by the National Science Foundation - which is an independent federal agency set up by US Congress in 1950 - the investigation suggested such feelings could be somewhat fuelled by genetics.

The researchers discovered that menstruating women are more biased against those of the opposite sex who are from different races and social groups then men from their own.

Melissa McDonald, a doctoral student at the institution, said: "Our findings suggest that women's prejudice, at least in part, may be a by-product of their biology."

The study also revealed such increases only took place when women perceived the men as physically threatening.

Dr Marilyn Glenville, Chartered Psychologist, commented: "The innate drive is to reproduce and previous research by the same team has shown that during the fertile time of the menstrual cycle, women were more attracted to men who were physically imposing but were of the same racial and social group.

"But in this research these same traits were seen as being negative in men of a different racial or social group.

"This could be seen as an evolutionary system which could have protected women and their social and racial group from unwanted reproductive choices in the past when women may have been sexually forced by male strangers when they were most fertile."