Women judge the attractiveness of other women more harshly when at their most fertile, suggests a new study. The phenomenon could be a strategy to devalue potential rivals, says the psychologist behind the work 鈥� being bitchy about others could help a woman win the attention of a desirable man.
Theories of sexual selection in most species usually concentrate on how males compete for females. But recent theories for humans suggest there is intrasexual competition among females as well, as males can vary markedly in their abilities as providers and protectors.
Maryanne Fisher, a psychologist at York University in Toronto, Canada, decided to try to find evidence for female competition by presenting heterosexual students with photos of faces. She found that when women were in the most fertile phase of their menstrual cycles, they rated the attractiveness of other women lower than when they were not.
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鈥淥ften women are characterised as being very co-operative, very kind-hearted and not competing directly,鈥� Fisher told New 杏吧原创. 鈥淏ut there鈥檚 been a fair bit of work on how women are indirectly aggressive.鈥�
For example, she says: 鈥淩ather than saying 鈥業鈥檓 going to beat that woman up because she looked at you鈥�, it鈥檚 鈥極h my goodness, look how fat her ankles are鈥�!鈥�
Caring or rugged
Being more combative during a fertile period backs the idea that women are competing for the best mate. 鈥淲hen you鈥檙e in a high fertility phase, you have to be more able to judge other women as potential rivals,鈥� says Fisher.
David Perrett, an expert on facial perception at St Andrew鈥檚 University, UK, says: 鈥淚t鈥檚 a very interesting finding. This is the first study I know of to find attitudes to female faces changing [with the menstrual cycle].鈥�
Perrett鈥檚 group previously found that women preferred more feminine, caring looking men for most of the month, but preferred more rugged, dominant looking types during the most fertile phase of their cycle.
In contrast, the women鈥檚 attitudes towards male faces did not appear to vary with the menstrual cycle in this new study.
Neutral expression
The 57 female students tested, along with male controls, were asked to look at colour photos of 35 female and 30 male faces. The models for the photos were asked to display a neutral facial expression, wear a black smock and remove any accessories to help standardise the experiment.
Women with high estrogen levels, in days 12 to 21 of their menstrual cycle, rated other women鈥檚 attractiveness significantly lower than women in a less fertile, low estrogen period of their cycle.
Fisher does not know exactly how women鈥檚 heightened sense of competition during ovulation may help them win a mate. 鈥淒oes putting someone down make you feel better about yourself? Or does saying it to a male make her less attractive to him?鈥� she asks.
She adds that this kind of intrasexual competition could also carry risks 鈥� being too bitchy could make a woman look 鈥� mean-spirited鈥� to a man. To answer these questions, Fisher is now investigating how men鈥檚 attitudes are affected by women using such derogatory tactics.
Ben Jones, a psychologist working with Perrett at St Andrew鈥檚, points out that Fisher鈥檚 results may not necessarily reflect simple derogatory tactics. Previous research has shown that women also rate their own attractiveness as higher when their fertility is high.
鈥淚ndeed, the fluctuations in women鈥檚 perception of their own attractiveness may reflect real physical changes caused by estrogen, for example lip colouration and fullness,鈥� he says. 鈥淪o the women may be objectively correct in seeing others as less attractive.鈥�
Journal reference: Biology Letters (DOI: 10.1098/rsbl.2004.0160)