Estrus is a phase of increased female sexual receptivity, proceptivity, and attractiveness that is common amongst mammalian species ( [Lange et al., 2002] and [Lombardi, 1998] as cited in [Miller, Tybur, Jordan, 2007] ). Its purpose appears to be designed to obtain sires of superior genetic quality ( [Gangestad et al., 2005] and [Thornhill, 2006] as cited in [Miller, Tybur, Jordan, 2007] ). Today, estrus in female humans has been said to have disappeared or been hidden over evolutionary time ( [e.g. Burt, 1992] as cited in [Miller, Tybur, Jordan, 2007] ). Correlational research assessed whether women’s ovulation cycles affected the amount of tips that lap dancers earned at a gentlemen’s club in Albuquerque. Through the study they found implications for human evolution, economics and sexuality and that it appears to still be present in females (Miller, Tybur, Jordan, 2007). Miller, Tybur, and Jordan stated that if estrus is still present in women, men tend to subconsciously tip more during lap dances. In addition they predicted that normally cycling participants would demonstrate a larger increase in the fertile phase relative to the other phases for pill-using participants (2007). The argument for using lap dances as a measure for estrus is that at a gentlemen’s club, all of the dancers are already motivated to earn as much tips as possible. If estrus is present in woman, the researches stated the dancers would earn more during this phase of their cycle and that contraception users would not get as much tips as regular cycling women. These estrus cues are unconsciously detected by males and manifested in women through a more attractive scent ( [Havlicek et al., 2006] , [Kuukasiarvi et al., 2004] and [Singh & Bronstad, 2001] as cited in [Miller, Tybur, Jordan, 2007] ), softening of skin ( [Manning, Scutt, Whitehouse, Leinster, & Walton, 1996] as cited in [Miller, Tybur, Jordan, 2007] ) decreased weight-to-hip ratio ( [Kirchengast & Gartner, 2002] as cited in [Miller, Tybur, Jordan, 2007] ), higher verbal creativity and fluency ( [Krug et al., 1999] and [Symonds et al., 2004] as cited in [Miller, Tybur, Jordan, 2007] ) and increased facial attractiveness ( [Roberts et al., 2004] as cited in [Miller, Tybur, Jordan, 2007] ).
The information was collected through correlational research. The researchers did not control any of the situational or person confounds, however, all research was conducted within a strip club where the setting was the same. Eighteen female participants (of which seven were on the pill while eleven were not) were recruited through indirect emails and asked to log their mood, work hours, work location, and tip earnings and when they had begun/ceased menstruation in a self-report for 60 days. Due to the intimacy of lap dances, men were, theoretically, able to pick up more of the estrus cues from women rather than, for example, using photographs of women instead
( [Haselton, Mortezaie, Pillsworth, Bleske-Recheck, and Frederick, 2007] as cited in [Miller, Tybur, Jordan, 2007] ). There were two independent variables in this study: first was the use of a contraceptive by the dancers and, second, the phase of their ovulatory cycle. The dependent variable was the amount of tip earnings they generated over the 60-day period.
Explicit results showing increased tips during estrus were achieved. The extent of these earnings was moderated by whether the dances were on the pill or normally cycling. It was shown that all women had lower earnings during their menstrual cycle where signs of fatigue bloating, muscle pains, and irritability may have affected results. Although both pill uses and regular cycling females had higher earnings during the fertile estrous phase, the pill uses had no mid-cycle peak in tip earnings like the normally cycling women did. The normally cycling women earned $354 per shift during estrus, while the results also showed that pill users made just over $200. On average,
