The robustness of social endocrinology: Pre-registered studies on testosterone in male mate competition and female menstrual cycle shifts in mating strategies
Biological Personality Psychology, Institute of Psychology, Georg August University Göttingen
In evolutionary psychology, steroid hormones have emerged as central proximate mechanisms that mediate functional social strategies and life history trade-offs, especially in the domain of mating and intrasexual competition. At the same time, such social endocrinology studies are often small, which makes them vulnerable in a time where the field of psychology becomes increasingly concerned with replicability. I will present two recent, comparatively large, pre-registered studies from our lab that take a closer look on central findings from social endocrinology.
Testosterone (T) is assumed to regulate competitive vs. nurturing behaviour, especially in mating contexts for males. How T-reactivity, also under potential buffering effects of Cortisol (C), relates to personality state changes is unclear. In a preregistered study, we aimed to induce T-increases in young men (N=125 plus a control group of N=40) through exposure to a potential mate and dyadic intrasexual competitions (e.g. arm wrestling). We investigated self- and video-based observer-rated personality state changes, as captured by the Interpersonal Circumplex, in relation to hormonal levels. Results revealed increases in self-rated competitiveness, while ingenuousness decreased, moderated by significant T-reactivity and T/C-interactions. Observer-rated dominance and extraversion increased, but unrelated to T or C. Thus, male personality responses to a competitive mating context occurred more in competitiveness/dominance and less in nurturance.
Estrus, or hormone-mediated changes of female mating behaviour across the ovulatory cycle, is well-established in most mammalian species, but controversial in humans. Perspectives range from a loss of human estrus to vestigial remainder effects to adaptive explanations, most famously a shift of sexual desire during fertility from primary partners to genetically fitter men. Studies in this area have recently been criticized for lacking methodological standards. In a pre-registered study, over 340 naturally cycling women and a quasi-control group of over 530 hormonally contracepting women, all in romantic relationships, participated in an online diary study for up to 35 days. We extensively tested results for robustness. We find ovulatory increases in extra- and in-pair sexual desire and self-perceived attractiveness. However, we do not replicate previously reported effects on sexual behavior and dress style, and find only mixed support for moderators like partner sexual attractiveness.