Hormonal contraceptive use lowers female intrasexual competition in pair-bonded women

a r t i c l e i n f o The purpose of this study was to test the influence of hormonal contraceptive use on levels of female intrasexual competition. Twenty-eight women completed a scale for intrasexual competition on three occasions: when using hormonal contraceptives and when regularly cycling at a fertile and a non-fertile cycle stage. When using hormonal contraception, pair-bonded, but not single women, reported significantly lower levels of intrasexual competition than when regularly cycling at either fertile or non-fertile cycle stages. This effect remained significant when controlling for age, length of relationship and relationship satisfaction. Neither pair-bonded nor single women reported shifts in intrasexual competition across the menstrual cycle when fertile as compared to non-fertile. This study benefited from a within-subjects design and a more rigorous assessment of fertility status (transvaginal ultrasonography) than which is typical in the field. Results are discussed in consideration of the evolutionary literature on the stability of romantic relationships and fitness advantages associated with intrasexual competition. Over 50 years have elapsed since the introduction of hormonal contraceptives (HCs). During this time a great deal of research targeting the study of physical risks associated with their use has been generated (e.g., Kiley & Hammond, 2007). A new but growing body of literature suggests that in addition to physical effects, HC use may also have various psychological effects. In particular, the use of HCs may alter female preferences for indicators of male genetic quality and compatibility (Alvergne & Lummaa, 2010; Roberts et al., 2008). For example, a study by Gangestad and Thornhill (1998) found that pill users do not show a preference for the scent of symmetrical men (an indicator believed to be associated with genetic quality), or changes in symmetry preference across the month when fertile. Moreover, studies investigating attractiveness ratings show that there is no variation in such ratings across the cycle in men rating contraceptive users or in contraceptive users' own preferences across the cycle (e. may potentially have evolutionary repercussions on relationship formation, long-term relationship satisfaction, and upon actual reproductive outcomes. In the present research, using a within-subjects design, we tested the influence of HC use on levels of female intrasexual competition. While studies investigating the impact of HC's typically compare between-subjects who are using HC and those who do not, using a within-subjects design is critical because women who use HC may differ on a number of dimensions …