Weird Science: It’s Friday!

For this Friday’s weird science I refer to a paper that we grad students were discussing a few months ago in a bar.  I find my weird science is always best when it comes from these places.   This week’s subject: Strippers. You know you wanna read now.

“Ovulatory cycle effects on tip earnings by lap dancers: economic evidence for human estus?” Miller et al, 2007, Evolution and Human Behavior

So as I’m sure most of you know, female mammals undergo estrus.  This is a phase just surrounding ovulation, when the female is more attractive to males and has increased sexual receptiveness.  In many mammalian species, estrus is advertised by enlargement of the genitalia or increased scent production, clueing the male into the fact that the female is hot to trot.  However, in humans, it appears that estrus became ‘hidden’ somewhere during our development (I keep mine in a special little box with hearts on it with all my other treasures).  It is thought that hidden estrus allows us to fool the male into sticking around and caring for us, influencing the formation of long term pair bonding (Strassman, 1981).  After all, if he doesn’t KNOW whether a girl’s in estrus, he has to stick around and keep trying. 

But estrus may not be as hidden as people think.  Apparently women who are in the most fertile period of their cycle smell more attractive to men (Singh and Bronstad, 2001), have a decreased waist to hip ratio, and ever exhibit more facial attractiveness (Roberts, 2004).  But the authors of this study point out that there have been very few studies that investigate the real-world effects of human estrus outside of the laboratory.  A couple of studies (Gangestad, 2002, and Haselton, 2006) show increased mate guarding behavior among males, but that’s about as far as they’ve gone.  So these researchers set out to see whether estrus in females changes their economic advantages by studying lap dancers.

Why lap dancers?  The authors rationalize that the girls are highly motivated to maximize their tip earnings during every shift, and so will be trying to appear more sexual attractive regardless of their estrus cycle point, as well as being equally flirtatious with their customers.  So they looked at two sets of lap dancers over a two month period.  What I really like about this article was the background of the lap dancing subculture “because academics may be unfamiliar with the gentlemen’s club subculture”.  Clearly, they don’t know some of the academics I know!

Basically, at the clubs they were looking at, women were required by law to wear underwear, bikinis, or thongs.   Dancers performed between 1 and 3 “stage dances” to advertise, with the rest of the time spent walking around asking if people want lap dances.  Lap dances are considered the most intimate form of legal sex work in most states, and cost between $10 and $20 at the clubs where the data was taken.  If you want to know what exactly occurs during a lap dance, I suggest you look it up yourself, though the article does a pretty good job of putting it in scientific terms. 

In this study, they recorded the tip earnings of two groups of dancers over a two month period, for a total of 296 work shifts resulting in 5300 lap dances (an average of 17.9 lap dances per shift).  One group was on oral contraceptives, which, though most allow women to ovulate, cause a flattening of the hormone curves associated with estrus, while the other group was on no oral contraceptive. 

So is estrus detectable in lap dancers?  They found that dancers who were on the pill exhibited fairly steady earnings throughout the month, with around $150/night earned in the menstrual phase, $200 in the fertile phase, and $190 in the luteal phase.  Fertile dancers, though they exhibited the same earnings in the menstrual and luteal phase, showed a spike in earnings at the fertile phase, earning around $300/night in comparison to the infertile dancers’ $200.  The net result was that, overall, the fertile dancers earned more money.

The authors conclude from their study that they have found economic evidence of estrus in contemporary human women.  Furthermore, they conclude that the men going to these clubs can tell the women are in estrus, and that is why they make more money.  They don’t explicitly state it in the paper, but it seems that they are pointing to the idea of phermones released by females during estrous which males are able to sense with compatible receptors.

A friend of mine who studies chemical sense systems (and who may or may not frequent gentleman’s clubs), had a couple of problems with this paper, and when I read it and talked to him about it, I see what he means.  Of course the phermones may be the case, there are lots of chemicals in the body we haven’t fuond yet, and lot of chemical receptors as well.  But wouldn’t the overwhelming (and usually nasty) smells found in a gentleman’s club (beer, smoke, perfume, sweat, etc) override the system?  Also, The tip earnings during the menstrual phase are low for both groups, but that could not be phermones so much as the fact that many women feel pretty crappy during “that time of the month”.  Some types of oral contraceptives can help with this, but often there are some symptoms anyway.  Finally, I understand their idea of using a strip club to do this, as a place where women are likely to try equally hard to be attractive on any given night.  But, given the evidence, there could still be differences during estrus.  Women in estrus are more self-confident, feel more attractive, and are rated as being more attractive to men, so it could be a female confidence factor, or a male visual factor (during estrus there are some changes in waist-to-hip ratio and facial attractiveness). 

I have two final thoughts on this:  1) we need to replicate this study!  I don’t think that I’d use strippers, though.  I think you’d have to find a profession where women are deliberately getting paid to be either standoffish or coldly professional, and see then if men rate them as being more attractive during certain times of the month.  I’m not really sure what profession would qualify.

2) Who came UP with this study?  I’m picturing a bunch of academics who may have been “more familiar with the gentleman’s club subculture” sittin’ around at the club one day saying “guys! guys!  we should WRITE THIS UP!!!”  Whoever came up with this study, especially if it was influenced by sometime other than a strict sense of academic curiosity, I salute you!

MILLER, G., TYBUR, J., JORDAN, B. (2007). Ovulatory cycle effects on tip earnings by lap dancers: economic evidence for human estrus?☆☆. Evolution and Human Behavior, 28(6), 375-381. DOI: 10.1016/j.evolhumbehav.2007.06.002