Which is perfectly correct.
Where the OP goes wrong in claiming that “With the pill there was no peak in earnings.”. With the pill the peak is relatively larger than without. It just doesn’t correlate with peak fertility.
This doesn’t surprise me. I’ve seen similar studies that just had men rate women’s attractiveness and realizing it correlates with estrous cycles. The offered explanation was that a woman who is fertile puts out more signals that she is available, which include dressing more provocatively.
Heck, that study or studies probably provoked this one.
they did. There appears to be several independent studies that show that the theory of hidden fertility in humans isn’t true. At least one (A paper by Haselton at UCLA to be published in “Current Directions in Psychological Science”, April Issue, 2011) refers to the study in the OP. Haselton’s study examines whether a human male can detect a human female’s fertility. A woman’s fertile time is observable and has consequences for both the woman herself (dress is more alluring according to one study) and to others observing her. It doesn’t seem too surprising.
I think it’s going way too far to attribute this to physiological changes. There are a number of much more simple explanations.
Think about it. What do you wear during your period? I feel gross and bloated, and usually wear my frumpiest clothes. If I were a stripper, I’d be wearing my thickest, sturdiest, darkest thong and not shake around too much. These are practical considerations that will affect my tips.
When your period ends, you feel a lot better and a lot more free, and you finally get to wear all the sexy clothes you didn’t want to ruin by bleeding all over. I usually do break out a cute dress when my period is over, and I think that has much more to do with me thinking “Man, I haven’t dressed up cute in a while. Let’s have fun getting dressed again.” LIkewise a stripper would enjoy her renewed freedom to wear filmy undies and move without worrying about dislodging anything. It’s kind of like how a prisoner out of jail might gorge on ice cream, take three hour showers, and buy all his friends drinks.
Of course, after a few days the excitement gets old and you fall into a “normal” routine, and things level out on a normal level. I get tired of tottering around in heels, but also dress up a notch from my “period pants.” The stripper falls into a routine and chooses from the middle range of her wardrobe. The released prisoner gets a job.
There are waaaaaaaaaaaaay too many factors to control for for the “women on birth control make less” finding to mean anything. Age, ethnicity, religious beliefs, attitudes towards sexuality, sexual orientation, health status…any number of these things can make a HUGE difference in both birth control and tips. A lesbian probably won’t be on birth control and probably won’t put her heart into dancing for men. A woman who was raised in a conservative family may not use birth control, but may have a psychological virgin-whore complex that puts some extra fire in her dancing. I’m absolutely certain ages and ethnicities are more likely to use the pill, and those might not correspond with the demographics that pull in the big tips.