Fertile-Window Facial Cues and Women's Mate-Guarding in a Multi-Target Social Scene

The proposed study examines whether partnered women selectively guard their romantic partners from women photographed in their fertile window. Building on Krems et al. (2016), who presented a single target woman and manipulated fertility between subjects, this study introduces a more realistic three-woman social scene and a triadic ranking task. Participants will view natural photographs of real women taken at pre-fertile, fertile-window, and luteal phases, with cycle phase manipulated within woman across participants. By ranking which woman appears most threatening, least trustworthy, and most deserving of partner-distancing, we will test whether fertile-window facial cues reliably heighten perceived rival threat.