Original Article Other women’s fertility moderates female resource distribution across the menstrual cycle Elizabeth A. Necka a, ⁎, David A. Puts b , Stephanie J. Dimitroff a , Greg J. Norman a a University of Chicago, Chicago, IL b Pennsylvania State University, University Park, PA abstract article info Article history: Initial receipt 6 July 2015 Final revision received 14 March 2016 Keywords: Fertility Menstrual cycle Intrasexual competition Ovulation Status competition among female mammals tends to intensify near ovulation. Females compete selectively, targeting females who most threaten their own likelihood of conception. The present study explored the extent to which regularly cycling women differentially compete with other women in a behavioral economic game as a function of both women’s fertility. We find evidence for an interaction between participant and target fertility, such that women withhold more resources from another woman, thereby keeping more for themselves, when both women are in the fertile (late follicular) phase of their menstrual cycle. Results expand research on women’s perceptions of fertility cues in other women by demonstrating a possible role for such cues in modulating female social behavior. © 2016 Elsevier Inc. All rights reserved. There are only approximately six days in the average premenopausal woman’s regular ovulatory cycle during which intercourse may result in conception (Wilcox, Dunson, Weinberg, Trussell, & Baird, 2001). During the late follicular (i.e., “fertile”) phase of a woman’s cycle, she is more likely to demonstrate mating-related psychology and behavior such as interest and engagement in, and potentially even initiation of, sexual behavior (Bullivant et al., 2014; Roney & Simmons, 2013). Near ovulation, women also tend to behave in ways that can increase their attractiveness to males, wearing revealing clothing (Durante, Li, & Haselton, 2008) and dancing and perhaps walking suggestively (Fink, Hugill, & Lange, 2012; but see Provost, Quinsey, & Troje, 2008). In addition to attracting potential mates directly, these behaviors may also divert male attention from other women. That is, these behaviors may be one way in which women compete with each other. Indeed, fertile women’s self-promoting behavior is elicited more by the presence of other women than of potential mates. For example, during their fertile phase, women preferred to purchase sexier clothing items when primed with images of attractive women, but not when primed with images of unattractive women or of attractive or unattractive men (Durante, Griskevicius, Hill, Perilloux, & Li, 2011). Other behaviors associated with aspects of competition have also been observed in women near ovulation (although see Cobey, Klipping, & Buunk, 2013), such as dehumanizing other women (Piccoli, Foroni, & Carnaghi, 2013) and giving other women fewer resources (Durante, Griskevicius, Cantú, & Simpson, 2014). 1 Furthermore, fluctuations in competitive behavior throughout the estrous cycle can be observed across species, with competition tending to be highest among female mammals near estrous (Stockley & Bro- Jørgensen, 2011). In yellow baboons (Papio cynocephalus), for example, ovulating and pre-ovulating estrous females are more likely to form attack coalitions against other females (Wasser, 1983). Moreover, pre- ovulating (but not ovulating) estrous females are more likely to be the targets of such attacks (Rowell, 1972; Wasser, 1983), the effect of which is an increase in the number of cycles before conception (Wasser & Starling, 1988). A negative association between adult sex ratio (females/males) and birth rate in this species suggests that some attacks may reflect female competition for mating opportunities (Dunbar & Sharman, 1983). Yellow baboons live in multi-male, multi- female societies in which females mate promiscuously with multiple males. By contrast, humans tend to exhibit mildly polygynous mating with a high degree of social monogamy. Within socially monogamous relationships, women may exhibit mixed mating strategies, seeking out extra-pair copulations with mates of higher genetic quality than their long-term partner during peak fertility (Gangestad & Haselton, 2015). To the extent that mating opportunities with males of high genetic quality are limited, women may therefore confront increased mating competition when they are near peak fertility. Successful intrasexual competition can increase opportunities to conceive and chances of offspring survival (Clutton-Brock & Huchard, 2013; Stockley & Bro-Jørgensen, 2011). However, intrasexual Evolution and Human Behavior 37 (2016) 387–391 ⁎ Corresponding author. Department of Psychology, University of Chicago, Chicago, IL 60637. E-mail address: enecka@uchicago.edu (E.A. Necka). 1 Because research in this area is often underpowered, extant findings should be taken as suggestive of a relationship between fertility and competition, but not as definitive. http://dx.doi.org/10.1016/j.evolhumbehav.2016.03.003 1090-5138/© 2016 Elsevier Inc. All rights reserved. Contents lists available at ScienceDirect Evolution and Human Behavior journal homepage: www.ehbonline.org