By University of Aberdeen, [RxPG] The new study has revealed that when progesterone levels are raised during the second half of the menstrual cycle, women become more committed to their romantic partners.
Dr Ben Jones, Lecturer in the Psychology department at the University of Aberdeen, is first author of the new study published recently in the American journal Hormones and Behavior.
He said: Its well established that womens preferences for the faces, body odours, voices and behaviour of feminine men increase during the second half of the menstrual cycle when progesterone level is raised.
One interpretation of these effects is that women are particularly attracted to feminine caring and sharing men at times when raised progesterone level prepares the body for pregnancy.
This maternal self-protection instinct increases the amount of support women receive during pregnancy and helps women meet the physical and mental challenges of pregnancy more easily.
Increased commitment to their partner when the body prepares for pregnancy is important because women face many physical and mental challenges during pregnancy, such as stress and physical discomfort, and care and support probably makes coping with these challenges a little bit easier, said Dr Jones.
Professor Dave Perrett from the University of St Andrews, who lead this new study together with Dr Jones, said: Our new research shows direct links between changes in progesterone and attitudes to both relationships and male looks.
During the second week of the menstrual cycle, when the pregnancy hormone progesterone is low, women are drawn to masculinity and commitment to long-term partners falters, but for the last two weeks of the cycle when progesterone is high, women are drawn to the health and caring looks in a man and commitment to partners strengthens.
Dr Jones added: An interesting aspect of this new study is that changes in womens commitment to their romantic partners dont seem to threaten the stability of their long-term relationships.
We found that womens commitment to their romantic partners changes during the menstrual cycle but that this does not affect how happy women are with their current partner.
The group are continuing to explore the effects changes in hormone levels have on attraction and attitudes and are planning their most ambitious study yet.
Dr Jones said: We plan to recruit couples that are planning pregnancies and track their attitudes to relationships and face preferences from before conception, right through pregnancy and into the first few months of parenthood.
By using the internet to collect this data we hope to track these changes in men and women from all over the world.