Original article
Ovulatory cycle effects on tip earnings by lap dancers: economic evidence for human estrus?

https://doi.org/10.1016/j.evolhumbehav.2007.06.002Get rights and content

Abstract

To see whether estrus was really “lost” during human evolution (as researchers often claim), we examined ovulatory cycle effects on tip earnings by professional lap dancers working in gentlemen's clubs. Eighteen dancers recorded their menstrual periods, work shifts, and tip earnings for 60 days on a study web site. A mixed-model analysis of 296 work shifts (representing about 5300 lap dances) showed an interaction between cycle phase and hormonal contraception use. Normally cycling participants earned about US$335 per 5-h shift during estrus, US$260 per shift during the luteal phase, and US$185 per shift during menstruation. By contrast, participants using contraceptive pills showed no estrous earnings peak. These results constitute the first direct economic evidence for the existence and importance of estrus in contemporary human females, in a real-world work setting. These results have clear implications for human evolution, sexuality, and economics.

Introduction

Estrus is a phase of increased female sexual receptivity, proceptivity, selectivity, and attractiveness. It is common across mammalian species (Lange et al., 2002, Lombardi, 1998), including primates (Dixson, 1998, Nelson, 2000), and seems functionally designed to obtain sires of superior genetic quality (Gangestad et al., 2005, Thornhill, 2006). However, the conventional wisdom holds that human female estrus became uniquely “lost” or “hidden” over evolutionary time (e.g., Burt, 1992), perhaps to promote male provisioning and paternal care in long-term pair-bonded relationships (Strassmann, 1981, Turke, 1984). Contrary to this “hidden-estrus” view, recent laboratory-based studies show that women near the most fertile point of their cycle (just before ovulation) are more attractive to males, as manifest through more attractive body scent (Havlíček et al., 2006, Kuukasiarvi et al., 2004, Singh & Bronstad, 2001), greater facial attractiveness (Roberts et al., 2004), increased soft-tissue body symmetry (Manning, Scutt, Whitehouse, Leinster, & Walton, 1996), decreased waist-to-hip ratio (Kirchengast & Gartner, 2002), and higher verbal creativity and fluency (Krug et al., 1999, Symonds et al., 2004).

While such laboratory-based findings are theoretically important, only four studies have, to our knowledge, investigated the real-world attractiveness effects of human estrus outside the laboratory.

Haselton, Mortezaie, Pillsworth, Bleske-Recheck, and Frederick (2007) photographed 30 young women—all in steady relationships and not using the pill—twice each, wearing their self-chosen clothing, once during estrus (as confirmed by hormonal assay) and once during a lower-fertility (luteal) cycle phase. Then, 42 mixed-sex raters made a forced-choice judgment (“In which photo is the person trying to look more attractive?”) between the two photos of each woman (with faces obscured, leaving only body and clothing cues). They chose the woman when she was in estrus about 60% of the time—modestly but significantly above chance. This result confirmed that both male and female observers are perceptually sensitive to women's choice of more conspicuous and fashionable clothes during estrus. (A related real-world study by Grammer, Renninger, & Fisher, 2004, found that mated women attending Vienna discotheques without their partners tended to dress more provocatively if they had higher estradiol levels; however, that study did not directly assess cycle phase.)

Gangestad, Thornhill, and Garver (2002) found convergent evidence that men's real-world behavior is sensitive to their female partners' estrous cues. (Note that estrous is the adjectival form of the noun estrus.) Among 31 mated women not using the pill, their sexual partners were reported as using more mate-guarding behaviors, including higher proprietariness, attentiveness, and vigilance (e.g., calling the women's cell phones at random times to see what they were doing) when the women were in estrus. This effect was especially strong when the relationship was not yet steady or exclusive—consistent with the theory that increased mate guarding of estrous women by male partners is functionally designed to deter extra-pair copulation.

Haselton and Gangestad (2006) replicated this mate-guarding result among 25 normally cycling women, using a stronger repeated-measures design based on daily reports. They further found that estrous mate guarding by male partners was mediated by both men's sexual attractiveness (less-attractive men mate guarded especially more during estrus) and women's own attractiveness (less-attractive women were especially mate guarded during estrus, whereas more-attractive women were mate guarded all the time). In a subsequent study, Pillsworth and Haselton (2006) found similar results on measures of male attentiveness and expressed love.

These four studies provide some evidence that men are sensitive to estrous cues in real-world situations. However, the photo-choice results were rather modest in strength (Haselton et al., 2007), and the mate-guarding results were rather indirect measures of estrous female attractiveness (Gangestad et al., 2002, Haselton & Gangestad, 2006, Pillsworth & Haselton, 2006). In this article, we build upon such research by presenting the first real-world economic evidence of male sensitivity to cyclic changes in female attractiveness. Specifically, we measured the tips earned by professional lap dancers in gentlemen's clubs over a 2-month span. These dancers are highly motivated to maximize tip earnings during every shift they work, which they do by appearing more sexually attractive than the other 5 to 30 rival dancers working the same shift and by doing the “emotional labor” of “counterfeiting intimacy” with male club patrons (Barton, 2006, Beasley, 2003, Deshotels & Forsyth, 2006, Pasko, 2002). Hence, if the hidden-estrus view is right, there should be no reliable cues of fertility available or expressed to patrons and no ovulatory cycle effects on dancer tip earnings. On the other hand, if women retain perceivable cues of estrus—if they become more attractive to male club patrons at midcycle, just before ovulation—then they might be in higher demand and earn higher tips.

Section snippets

Background

Because academics may be unfamiliar with the gentlemen's club subculture, some background may be helpful to understand why this is an ideal setting for investigating real-world attractiveness effects of human female estrus. The following information was gathered from interviews with local club managers and from the sociological and feminist literature on erotic dancing (Barton, 2006, Beasley, 2003, Brewster, 2003, Deshotels & Forsyth, 2006, Enck & Preston, 1988, Forsyth & Deshotels, 1997, Hall,

Methods

Participants were recruited through indirect e-mails (forwarded through local industry contacts), newspaper advertisements, and flyers posted near clubs. To minimize possible response biases through demand characteristics, we mentioned the ovulatory cycle only in recruitment and consent and we did not suggest that tip earnings would be examined specifically as a function of days since menstrual onset. We believe that this brief mention of possible cycle effects on tip earnings in the consent

Participant demographics and traits

The 14-page questionnaire completed by each participant gave extensive background information, only some of which is relevant to this study. All participants were exclusively or primarily heterosexual. All women reported regular cycles of 28–30 days; 7 were using the hormonal contraception pill, and 11 were not (and had not within the previous 3 months); none used any other form of hormonal contraception (e.g., the patch or the implant). On average, participants were 26.9 years old (S.D.=5) and

Discussion

We found strong ovulatory cycle effects on tip earnings, moderated by whether the participants were normally cycling. All women made less money during their menstrual periods, whether they were on the pill or not. However, the normally cycling women made much more money during estrus (about US$354 per shift)—about US$90 more than during the luteal phase and about US$170 more than during the menstrual phase. Estrous women made about US$70 per hour, luteal women made about US$50 per hour, and

Acknowledgments

We thank Rosalind Arden, Bernadette Barton, Juliana Beasley, Steve Gangestad, Vlad Griskevicius, Martie Haselton, Catherine Salmon, Ursina Teuscher, Randy Thornhill, Rhiannon West, and several anonymous reviewers for helpful feedback on this article.

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    Brent D. Jordan's contribution to this project was supported by a McNair/ROP Scholars Program Fellowship.

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