In the days around ovulation, women are usually fertile. Do you behave differently at this stage than usual? Recent studies contradict the popular theory that women prefer a different type of man in the middle of the cycle, reports psychologist Lars Penke from the University of Göttingen. But he and his team were quite able to observe cyclical changes in the female psyche.
Professor Penke, could you explain briefly and briefly what happens in the body of a woman in the course of a menstrual cycle?
Lars Penke: A woman's menstrual cycle is controlled by sex hormones. The body releases the hormones in a certain sequence over about 28 days. This hormonal cycle ensures that an egg cell matures and women are fertile for a short time. If the egg cell is not fertilized, it is broken down again with the uterine mucosa and menstrual bleeding occurs.
Why are psychologists interested in it?
We research how experience and behavior changes over the menstrual cycle. The messenger substances that control the cycle gets into the brain via the blood into all parts of the body. There they bind to receptors and thus influence our experience and behavior. Above all, the level of estradiol and progesterone fluctuates, an estrogen and a progestogen. These are sex hormones that occur in significantly higher doses in women than in men. The special thing about this research is that with the hormones we have a physiological substrate that triggers the psychological effects and that we can measure.
How do you do that? How do you determine which phase of the cycle the women are in?
The most direct way is to measure the hormones in the blood. But this is quite time-consuming. That's why we work a lot with saliva samples. The values that are obtained there are delayed by a quarter of an hour, but for most studies this makes no difference. Of course, you can also ask the women to observe their cycle themselves, provided that they do not take hormones and have a regular cycle. The standard cycle is 28 days long and usually varies between 24 and 32 days, but there are also larger outliers. You then calculate the ovulation backwards starting from the following menstruation, because the phase after ovulation is more constant than the phase before. Nevertheless, this method is comparatively inaccurate. The gold standard would be to measure in the morning urine the luteinizing hormone that triggers ovulation. It rises rapidly about a day before and falls again just as quickly after that.
Can you also observe ovulation directly?
This would be possible by ultrasound, but this is too time-consuming and invasive for our research. Some women even perceive ovulation themselves. This is because the oocytes are the largest cells in the body, so the cellular processes may be noticeable under certain circumstances.
Can you see a woman from the outside whether she is fruitful?
In many species, the females are only fertile and sexually active in phases, so they clearly indicate this. In our closest relatives, for example, the chimpanzees and bonobos, there are clearly visible changes in this phase, such as rectal swelling. A whole branch of research has therefore searched for such hints in humans – in vain. For a long time it was believed that ovulation in women is hidden so that men can not know exactly which offspring are their own. Our babies need care for a very long time, and paternal support helps in this. But if men knew exactly when a woman is fertile, it would be easier to look for a fertile woman again and again. If you do not know this, it is tactically wiser for passing on one's own genes to focus on only one female and her offspring.
And there is actually no recognizable hint?
There may be minimal effects as far as the redness of the facial skin is concerned, but so weak that they are not visible to the human eye. Everything was examined: the appearance, the smell, the tone of voice, the behavior. For example, do women tend to wear red clothes in the middle of the cycle? There were initial indications, but the findings were not confirmed. A lot of things have been checked over the past seven years. According to them, the cycle psychologically does something with women, but not in the way it is supposed to.
The most discussed question was whether the preferences change in the choice of partner: Do women around ovulation find a masculine male type more attractive? There were also studies in well -known journals like "Nature". Pictures of men by computer have changed so that the facial features or the physique were more or less masculine, and the female test subjects should state which picture they liked better. Similarly, you were looking for preferences for deep voices or a dominant behavior. In 2014 there was a meta -analysis; She confirmed the idea of a "dual sexuality" of the woman.
What is meant by this?
According to this theory, the sexuality of the woman serves more of reproduction on the fertile days, then the woman prefers men with the "best genes". For the rest of the time, sexuality is increasingly designed for social function, i.e. the bond in the couple relationship. A woman with a caring partner would therefore find masculine men around ovulation more attractive. And men should be able to recognize these phases and then strive. These assumptions have checked various working groups, including our in recent years with extensive studies. Almost nothing could be confirmed. The idea of a double sexuality is refuted, the burden of proof is overwhelming.
But you have also found cyclical changes?
Yes. The most robust effect concerns sexual interest: women have more desire for sex. But her taste of men remains the same. We tested in a study whether your preferences change across the cycle. The result was: Women find all male bodies a little more attractive near ovulation. So it is about the sexual interest in general, according to Freud "libido" or "sex drive".
What about women's interest in women's bodies?
In general, heterosexual women can also find women attractive; They are not as much fixated on the other gender as heterosexual men. The effect described, the increasing attraction in the middle of the cycle, only applies to male bodies. Unfortunately, there is almost no psychological cycle research for homosexual women. On the one hand because the theories are about evolutionary advantages, on the other hand because it is difficult to recruit larger homosexual samples, especially for the rather complex cyclus studies.
What does it look like when women take the pill?
You will not find the changes in the middle of the cycle. The hormonal contraceptives roughly prevent ovulation by keeping the hormones more constant, and so the psychological changes do not go. However, there are effects that have to do with physical discomfort during menstruation: in this phase, the sexual interest tends to decrease in women who take the pill. Of course, psychological effects such as the premenstrual syndrome can also be found in them.
Back to the women who do not use hormonal contraception. Do the fertile days show up in any other way than in the increasing sexual interest?
The biggest effect is definitely that you are more interested in sex with your own partner as well as potentially with other men. In addition, women around ovulation also find themselves more attractive. According to new findings, this is also reflected in self -confidence, so that women can become more dominant and researchers. And another effect is quite robust: in the second half of the cycle, between ovulation and menstruation, the women report that they eat more. There is even evidence that the weight fluctuates by 200, 300 grams. This could also be due to increased water retention. But you can also find an increased appetite in other species, for example with rhesus monkeys. If you offer them cookies, eat more of it in the second half of the cycle.
Do the psychological changes also manifest themselves in social behavior, for example by more desire for parties?
Yes, but much weaker than the increase in sexual interest. And that's not enough except for the level of clothing. Regardless of whether you look at photos or whether you let women draw what kind of outfit they would like to wear if they would go out today: we have not found any differences between the cycle phases.
Is there nothing wrong with the myth that waitresses get more tips around ovulation?
I have already read about this in the press, but as far as I know, a scientific study does not exist. However, there was a similar investigation by Geoffrey Miller in New Mexico with lapdancers, i.e. women who earn their money to dance slightly dressed in front of individual men. In an online diary you noted how much tip you deserved in a layer and when your last menstrual period was. Women who did not hormonal were therefore given much more tip around the ovulation. The sample was not great, but the study caused a sensation. As far as I know, the result has not yet been replicated.
All these findings relate to women who can have children. What happens when you get older?
The findings described are limited to the reproductive lifespan to menopause, i.e. the last menstrual period. Then the hormone cycle stops and thus also the psychological effects. Incidentally, there are only a few other species that, like us, have an ovulation cycle and menopause, Belugas and Narwale, for example. In evolution, it prevailed that women cannot get children into old age. On the one hand, the risk that you can no longer raise your children increases, on the other hand it helps your grandchildren if you are available as a grandmother. The effects triggered by hormones are also expensive, only a healthy body can afford it. That is why the sick and malnourished women release fewer hormones. But even regardless of age and fitness, there are big differences between women. Some experience very clear psychological effects around ovulation, others none at all.
According to traditional ideas, the cycle is more a women's affair. Does it happen that other people find it strange that you, as a man, deal with it so thoroughly?
No, the topic interests many, and it is considered rather emancipated that I, as a man, am well versed in it. But I also deal not only with the cycle, but in general with hormones and their effect, for example with testosterone in men.
What fascinates you so much about hormones?
They look very wide on body and psyche. They put us in a kind of different mode, just like emotions. For example, if we feel fear, everything else becomes unimportant - even physiology works differently. It is similar with the hormones: if men have a high testosterone level, they usually behave more dominant, competition -oriented, less caring. Above all, I'm interested in what that is actually good for. We were optimized by evolution. It is no coincidence that our bodies are as they are.
