Kate of Anterior Commissure wrote about a study showing that lapdancers earn more money when they're in the fertile part of their menstrual cycle. Moreover, women with stable hormones thanks to birth control pills earn less than normally cycling women.
The study put this down to "cues" somehow "leaking" out in the interaction between the man and the woman writhing around all over his airspace. Katie, on the other hand, thinks another study may provide a clue.
Could it be that these females (albeit, uh, provocatively dressed during all dances) were dressed any differently or made themselves up more for the dances performed around estrus, without realizing it? [Update: Or, per deepstructure's suggestion, perhaps fertile females are a bit more "enthusiastic"dancers?]
I think it's the smell. Or, to be more exact, the transfer of molecules between the two people, and their brains' on-the-fly chemical analysis.
Most mammals have a special area in the nose called the vomeronasal organ. This sensitive tissue, located in the nasal passages, sends molecules that the animal inhales directly to the brain, where they can influence behavior. This organ reacts to pheromones, the chemical signaling substances put out by animals from insects to apes. It's the organ that draws a female elephant to the musth secreted by a bull in his prime.
Human fetuses have a vomeronasal organ, and for a long time biologists thought that it was a vestigial structure that disappeared by birth. But recently, researchers have found evidence that the human response to pheromones is alive and well in adults.[i - I am going to let y'all look up these studies yourself.] This is the organ that seems to be responsible, for example, for the tendency of women living together to synchronize their menstrual cycles.
More sex and bonding chemicals may be exchanged via lovers' sweat and saliva, according to preliminary research by Cameron Muir of Brock University.[ii] How we react to the chemicals coming off another person's skin seems to be related to our sexual orientation.
Another study found that the brains of gay men and heterosexual women reacted the same way when they inhaled a testosterone-related compound found in male sweat. A part of the hypothalamus that's different in men and women became activated when these two groups got a whiff of that manly odor, piquing the hypothalamus.[iii] The brains of straight men, straight women, and homosexual men all reacted the same way to lavender oil and cedar oil, the control odors.
Lesbian women, on the other hand, were like heterosexual men in their response to inhaling an estrogen-like compound. Their hypothalami didn't light up at all when they got a whiff of the male scent.[iv]
In another 2005 study, neuroscientists Charles Wysocki and Yolanda Martins of the Monell Chemical Senses Center asked 82 men and women, heterosexual and homosexual, to sniff samples of underarm sweat collected from 24 donors. Like the subjects, the odor donors were male and female, gay and straight.
The gays and lesbians had patterns of body odor preferences that were different from those of the straight men and women. The gay men had the strongest partiality, preferring the B.O. of other gay men and heterosexual women. [v]
Given all this, it's not a stretch to think that the gentleman's club could be a hothouse for hormone-swapping.
[i] Smith, Timothy D. and Bhatnagar, Kunwar P., The human vomeronasal organ. Part II: prenatal development Journal of Anatomy (2000), 197: 421-436
[ii] Holland, Giles, Hot Sweaty Sex: Investigating the ins and outs of human chemical communication (Research Reporter No. 27, March 2006)
[iii] Savic, Ivanka; Berglund, Hans;and Lindström, Per, Brain response to putative pheromones in homosexual men (Neuroscience May 9, 2005, 10.1073/PNAS.0407998102)
[iv] Berglund, Hans; Lindström, Per; and Savic, Ivanka, Brain response to putative pheromones in lesbian women (PNAS, May 23, 2006, Vol. 103, No. 21, pp. 8269–8274)
[v] Wysocki, Charles, Gender and Sexual Orientation Influence Preference for Human Body Odors, Monell Chemical Senses Center press release, May 9 2005