Science in the Lap of Luxury

As anyone who has ever kept a female dog knows, at certain times of the year she becomes the focus of affection for any male canine within sniffing distance. It's because she is "on heat", which is another name for the mammalian oestrus, a time when animals advertise their fertility and attractiveness to the opposite sex.

So does this happen to us? Prevailing wisdom says not and that evolution has abandoned the process in humans. After all, we're far too civilised to be obsessed with womens' rear ends, aren't we? Apparently not, because thanks to a team of lap dancers in Albuquerque, it looks like the human oestrus is a myth no more.

Geoffrey Miller and his colleagues at the University of New Mexico hypothesised that if women do subconsciously advertise their peak fertility in some subtle way, then men ought to find them most attractive at this time. And if that's the case, then in a setting where men have to buy a lady's attention, such as in a lap-dancing club, then the woman's earnings from tips ought to peak in line with her fertility during her menstrual cycle.

So, to test out their theory, the New Mexico team recruited 18 local lap dancers and asked them to keep a daily tally of their earnings over a 60 day period. At the same time the women recorded the stage of their menstrual cycles and whether or not they were using the oral contraceptive pill. The pill works by fooling a woman's body into believing that she is pregnant, which prevents ovulation and the other hormone changes that accompany the process, so it could have an effect on how attractive men find women to be.

The results of the study were striking. The earnings of the normally-cycling (non pill-using) lap dancers nearly doubled to US$350 per shift around the times when they ovulated and were therefore at their most fertile. Then, as they approached menstruation and their fertility fell, their earnings declined to a baseline of about US$200 per shift.

The pill-users, by comparison, fared less well. They earned a flat average of US$200 per shift throughout their cycles - but why? Were the pill-using women just less attractive than their non contraceptively-compromised counterparts? "No," say the researchers, because both groups earned approximately the same amounts at the beginnings and ends of their cycles, indicating that the effect was not due to an overall difference in attractiveness.

Instead the results suggest that men can subconsciously detect when women are at their most fertile and judge them to be more attractive, valuable and, it would seem, worthy of more attention and larger tips at this time. The researchers don't yet know what triggers the effect. It could be down to altered behaviour on the part of the fertile woman, such as chatting engagingly or wearing more provocative clothing and make up, or it might be that chemical cues, like pheromones, are responsible.

Either way, as Miller points out "this is the first time that anyone has shown direct economic evidence for the existence and importance of oestrus in human females." But the bottom line would appear to be ladies, if you want that new car at a knock-down price, consider ditching the pill, timing your approach to coincide with day 14 and always head for the male sales assistant...