Steven W. Gangestad - US grants

Recent research indicates that women's mating preferences change across the menstrual cycle. Women's preference for the scent of men who exhibit developmental instability, as revealed by low fluctuating asymmetry, is enhanced in the days leading to ovulation, as is women's preference for masculine male faces. A working interpretation of the findings is that women experience heightened attraction to indicators of benefits that could be heritably passed on to their offspring when they are fertile. Traits that indicate such benefits could be ones that may be generally associated with health (e.g., low fluctuating asymmetry), complement a female's set of genes (e.g., complementary major histocompatibility complex [MHC] alleles), or diversify offspring (e.g., diverse MHC alleles). The research is designed to test four hypotheses: 1) If women's preferences shift during the fertile period toward indicators of heritable benefits, which in-pair partners may not possess, women should experience greater attraction to men other than their primary partners during these days. Overall, women should not experience the same increase in attraction to their primary partners during this period. 2) Men may have evolved to be more attentive of their partners during these times. 3 & 4) Women's greater interest in men other than a primary partner and men's increased attention to their partners may be conditional; it may depend on whether a primary partner possesses heritable benefits (e.g., low fluctuating asymmetry, complementary MHC alleles, diverse MHC alleles). Six studies will assess these predictions in two cultures. One set of studies will assess changes in a sample of 200 romantically involved U.S. college students. The other set will examine the changes in a remote village on the Caribbean island of Dominica. The latter study will also examine whether female or male partner cortisol or the male partner's testosterone change across women's cycle. The aim of this program of research is to increase our understanding of the factors that affect partner choice, the dynamics and stability of relationships, and fertility.

In national and worldwide surveys, people regularly rate family and relationships as among the most important things in life and greatest sources of satisfaction and happiness. Yet romantic relationships are also great sources of personal distress. Their dissolution involves great costs to individuals and society (e.g., through loss of productivity, burdens on health services, negative impacts on children). An appreciation of what affects the well-being of relationships requires an understanding of relationship dynamics. Relationship dynamics, in turn, can be affected by women's hormonal status, as it changes through the cycle. A variety of evidence suggests women's social motivations are predicted by levels of ovarian hormones (notably, estrogen and progesterone), as they change across the cycle. During the non-conceptive phase following ovulation, progesterone levels increase. During this time, women may become more sensitive to the well-being of their relationship. Moreover, although oxytocin - a hormone that is thought to play key roles in maintaining close relationships, circulates through women's bodies throughout the cycle. This hormone may particularly affect their attention to partners when progesterone levels increase. Yet no research to date has explored specifically how ovarian hormones and oxytocin might affect relationship dynamics across cycles. This research aims to do so by examining how hormones influence changes in behaviors that strengthen relationships over time, which could enhance public well being.

A sample of 260 naturally ovulating women (ages 18-35) who have been involved in romantic relationships lasting at least 3 months will be recruited for the study. They will participate in 4 sessions, with sessions scheduled to be held at different points within women's cycles. A first session will assess women's own involvement in their relationships: their satisfaction with it, their commitment to it, their passions for it, and the ways they seek to nurture it. Women's views of their partner's involvement will also be assessed. In all 4 sessions, women will be asked about the frequency and intensity of events in their relationship: their particular interests in their partner and in men other than their partner, their concern for intimacy more generally in their relationship, and their efforts to seek intimacy with their partner. Women will also engage in a 10-minute thought-listing task about the relationship, which previous research has shown to produce an oxytocin response (assessed by measuring the hormone in saliva both before and after the task), contingent on relationship involvement. Hormone levels (estradiol [a form of estrogen], progesterone, testosterone, cortisol) will be measured in urine samples collected each session. Statistical analyses will examine how these hormone levels and oxytocin response, both by themselves and in combination, are associated with events key to understanding relationship dynamics, as they vary over time. These findings could provide insights into ways that relationships are strengthened or weakened, and affect public well being.