Thursday, February 19, 2009

perhaps a shift in soft tissue body symmetry?

Ovulatory cycle effects on tip earnings by lap dancers: economic evidence for human estrus?
Geoffrey Miller, a, , Joshua M. Tybura and Brent D. Jordana

Evolution and Human BehaviorVolume 28, Issue 6, November 2007, Pages 375-381

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.

very interesting stuff, plus I learned a lot about the world of gentleman's clubs.

from background:
Club patrons will often “sample” several different dancers with one lap dance each before picking one for a more expensive multisong bout of dancing. Thus, patrons can assess the relative attractiveness of different women through intimate verbal, visual, tactile, and olfactory interaction, and those attractiveness judgments can directly influence women's tip earnings, through the number of 3-min dances that patrons request from each dancer. In these ways, estrous attractiveness effects on lap-dancer earnings in gentlemen's clubs may be stronger than in other kinds of psychology research that use photo ratings (e.g., Haselton et al., 2007) or other kinds of sex work (e.g., visual pornography, phone sex) that give fewer fertility cues across fewer modalities.

from 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 menstruating women made about US$35 per hour. By contrast, the pill users had no midcycle peak in tip earnings. As in other previous research, the pill eliminates peak-fertility effects on the female body and behavior by putting the body in a state of hormonal pseudopregnancy (e.g., [Gangestad et al., 2004], [Gangestad et al., 2005] and [Macrae et al., 2002]). This also results in pill users making only US$193 per shift compared to normally cycling women making US$276 per shift—a loss of more than US$80 per shift.

This is the first direct economic evidence for the existence of estrus in contemporary human females.

A final limitation is that our study did not identify the precise proximal mechanisms that influence tip earnings. These might include the previously documented shifts in body scent, facial attractiveness, soft-tissue body symmetry, waist-to-hip ratio, and verbal creativity and fluency—or they might include shifts in other phenotypic cues that have not yet been studied. We can, however, exclude some possible mediators based on previous exotic dancer research. Tip earnings are unlikely to be influenced by cycle shifts in stage-dance moves, clothing, or initial conversational content because these cues just do not vary much for professional dancers ([Barton, 2006] and Beasley, 2003 J. Beasley, Lapdancer, PowerHouse Books, New York (2003).[Beasley, 2003]). The tip earnings pattern in Fig. 1 is similar to the pattern of estradiol levels across the cycle (with a main estrous peak and a secondary midluteal peak); hence, it is plausible that estradiol levels might mediate the tip-earning effects.

Perhaps, most importantly, from an evolutionary viewpoint, further research could clarify whether women have evolved special adaptations to signal estrus through such cues—or whether the cues are “leaking” to sexually discriminating men as unselected side effects of cycle physiology. Distinguishing between estrous “signals” and “leaked cues” may be difficult in practice because estrous females (seeking extra-pair copulations with good-gene males) and extra-pair males (offering good genes) may have shared interests in female fertility signals being “conspiratorial whispers” that are accurate but inconspicuous (Pagel, 1994). In serially monogamous species such as ours, women's estrous signals may have evolved an extra degree of plausible deniability and tactical flexibility to maximize women's ability to attract high-quality extra-pair partners just before ovulation, while minimizing the primary partner's mate guarding and sexual jealousy. For these reasons, we suspect that human estrous cues are likely to be very flexible and stealthy—subtle behavioral signals that fly below the radar of conscious intention or perception, adaptively hugging the cost–benefit contours of opportunistic infidelity.

When Chess Bitch came out, Rowson's NIC review of it made a point something like 'feminists shouldn't shy away from a discussion of the effects of menstruation on chess because people do talk/think about it, and better to have a reasonable discussion*.' It seems like this should be pretty easy to look at, if you have a dozen female players who have regular cycles and are willing to tell you about them and let you compare to their rating history. (I tried looking at my own before writing this, but despite playing ten reasonably long tournaments this year, it seems like I didn't have my period at any of them. what a shame. )

Let me just add, I think you might see no effect at all on performance, i.e. I'm not suggesting it's a terribly important study, just a relatively easy one to do, at least non-rigorously. (Certainly one should expect to see far far less of an effect than you would see in a stripclub.)


prosephina said...

I read that study when it just came out, but didn't relate it with chess at all. Maybe menstruation it self does not have much to do with playing strength per se, but PMS'ing or ovulating might! Do you play better when you're mad? Or so PO'ed that you tell yourself "oh there's no way that guy's getting out of this game alive!" before you even start playing the game...

Or eh, could just be me. :)

ATH2044 said...

It seems to me that you'd need an awful lot more data to come to any credible conclusions. The reality may be that things like PMS have more effect on whether someone would choose to participate in a tournament. That would skew the pool of contestants. Also, I'd expect (hypothesis here) these effects to be less pronounced when women compete against each other rather than against men. Now that I think about it, depending on what your personal metaphor for chess competition is, that could be the exact opposite. Do women prefer losing to other women rather than to men more so during certain parts of their cycle? Are there times when they show an increased preference for winning regardless of their opponent's gender?
How many conscious decisions do women make based on their menstrual cycles that would distort or obscure any hormonally driven ones? Perhaps there are times when their emotional responses to winning or losing a game may affect their ability to perform well in the next round; this may vary with hormones more for some women (people) than others.
The relatively few times I've been paired with female opponents, it never occurred to me that the outcome or potential difficulty of the game depended on her menstrual cycle. I guess we need more data there too.

Elizabeth Vicary said...

I definitely hope that the next time you play me, that you give that some thought.

Elizabeth Vicary said...

during the game, of course

Anonymous said...

Probably not a simple causal relationship: competing in a chess tournament may itself affect the timing of the menstrual cycle.

Funny that a silly little board game can trigger the fight-or-flight mechanism....

Anonymous said...

Actually chess would be an ideal of testing this theory - one could compare OTB performance versus games played over a computer - The internet games would be blinded for sex, age, and pheromones, estrus or whatever witchcraft could be at work. I'm sure someone somewhere will be applying for a grant to study this effect

Elizabeth Vicary said...

ok, two points on which I would disagree with the last two commenters:

1. playing in a chess tournament is highly unlikely to affect a woman's menstrual cycle. It can be affected by extreme stress (but playing a board game doesn't count below the professional level, I'm talking about sustained severe anxiety), lack of calories, or (urban legend from childhood, don't know if it's true) close proximity to other menstruating women.

2. I would guess if you see a cyclical effect on the performance women chess players, it's likely to be fairly independant of the sex of their opponent (since over the chess board there is not overly sexual interaction, as there are in strip clubs).

Elizabeth Vicary said...

overtly, not overly

Anonymous said...

No overtly sexual behavior?? Are you kidding?! At my very last tournament I was paired against this twentysomething hottie. She looked quite a bit like Buffy the Vampire Slayer, only better. Dressed like her, too. And she had the white pieces.
1.e4 Nf6
Actually, I intended to play 1...e5, but I was momentarily distracted by a certain someone brushing her long, silky hair, which smelled like flowers, and mistakenly grabbed the horsie. No problem: let her build her center and I'll tear it down.
2.e5 Nd5
3.Nf3 ...
Well, what's the book move here? Did she forget d4? Our eyes meet briefly, and she flashes an awkward smile, puckering her lips for an instant before tossing her head back with a little giggle. Damn her!
4.Bc4 ...
Sunflowers. No, Eternity? Or maybe it's Liz Claiborne. Hard to tell unless you're right up close. Huh? Defend or retreat the knight? Oh dear God, she's stretching...
5.Bxf7+ ...
As she reaches over to capture on f7, I catch a serious eyeful. What is it about cleavage that draws me in like a moth to a flame? I clasp my hands over my forehead to focus on the board. Hey, I'm in check. And what's that? A partially exposed nipple?! Gasp!
Okay, must concentrate. Where do I go with my king? Well, e8 looks like then there's g6 or g8.... Suddenly I'm aware of five delicate little toes running down my shin. Chest pains...shortness of left side is numb... Aaaugh!
7.Qf3 Kxg5
8.h4+ Kh6
9.Qf4+ Kg6
"Thanks for the game," she chirped as she extended her hand toward my smoldering corpse. Just as I thought - Sunflowers!

Anonymous said...

That was brilliant! Even the game! The whole piece belongs in Chess Life. (Unfortunately, they won't be able to print it. The kid readers, you know...)

I recall once getting distracted watching Martha Fierro make faces at the board, but nothing like that!

As for Liz - I really don't mean to be a bastard, but....I must confess to some surprise at hearing she has periods at all. My wife once told me that during her own late-20s, workout-obsessed phase, she got so thin her periods stopped altogether.

Anonymous said...

Seeing the string brush across your leg can lower the tip you want to give as well...

ATH2044 said...

Most likely I'd give it very little thought unless I were getting a lap dance during the game, but I think we need more data there too. One way to accomplish this would be to have next year's amateur teams consist of four chess players (with an average rating below 2200 of course) & one stripper. While the players compete, the stripper would give lap dances to the opposing team during the game.
A refinement might be that the lap dances could only happen when that person's clock was not running, so a lower rated team with an extra agile stripper could possibly out compete a tougher team by creating more average distraction. The idea of a stacked team would also take on a new dimension.

Anonymous said...

Re trying to play chess while getting a lap dance: There is an analogous scene in the great John Travolta film, "Swordfish."

Both sides of the analogy involve a different activity - each similar in content to competitive chess and lap dancing respectively, but raised to the Nth power.

And the stakes were a bit higher than the clock-prizes that go to winning Amateur Team members. As I recall, if the guy in "Swordfish" failed to solve his assigned task while being "lap danced" he would be immediately killed.

Elizabeth Vicary said...

wow, that would be like an adult tournament.