Do aunts really infect each other
4hw.org: I believe that many female friends are confronted with the problem of "infection" from their aunts. The menstrual cycle of women who are close to each other will gradually approach, or even synchronize. This sentence has become a secret thing for women. However, will aunts really infect? Will aunts infect science?
Intimacy keeps aunts in sync?
In 1971, McClintock, a psychologist, published his research in the famous scientific journal Nature, saying that women living in the same house tend to have menstrual cycle convergence. She selected 135 resident students from a women's University and divided them into roommate group, close friend group and random group. After six months of intimacy, McClintock made group statistics on their menstrual tide days (the first day of menstruation), and found that the tide days interval between the roommate group and the close friend group changed from 7-10 days to 3-7 days, with the cycle approaching. As a control group, the diurnal interval of incoming tide was 6-14 days and 5-15 days, basically unchanged. Based on similar phenomena in other mammals, such as the 'Whitten effect' in mice (pheromone released by male mice can synchronize the estrus of female mice), McClintock believes that the most likely cause of this phenomenon is pheromone.
The results of this study have led to a large-scale discussion, which is also known as the 'McClintock effect'. In the following decades, many scientists have studied this phenomenon, many of them have got the results consistent with the 'McClintock effect', the research scope covers sisters, colleagues and even homosexual couples. The methods used in these studies also basically refer to McClintock's practice in that year, that is, to make statistics on the difference of women's coming days in a period of time.
Although there are many research results that show the correctness of 'McClintock effect', there are also some studies that show that there is no obvious phenomenon of menstrual synchronization. In addition, the cause of its formation has not been confirmed for many years, the subsequent criticism of research methods, and the unknown evolutionary significance have all put a question mark on the correctness of 'McClintock effect'.
Question 1: the magic and mysterious pheromone, what can I take to 'smell' you?
In various studies of menstrual synchronization, we can easily catch a key word -- pheromone, which is considered to be the main cause of 'McClintock effect'.
Pheromone is actually a transliteration of pheromone, also known as pheromone. In 1959, German biochemist Peter Karlson and Swiss entomologist Martin lusher coined the term and defined it as' substances secreted by one individual into the body, received by other individuals of the same species and affecting their physiology or behavior '.
There are many kinds of pheromones, among which the most familiar one is the number pheromone. Many insects release sex pheromones to attract the opposite sex, and some orchids mimic the sex pheromones of female wasps to attract males to pollinate them. At present, many researches think that the recognition of sex pheromones is mainly related to vomeronasal organ (VNO), not through olfactory epithelium. Many mammals have vomeronasal organs, such as elephants and mice, whose behavior has also been shown to be influenced by pheromones - but humans do not have vomeronasal organs.
So the mysterious pheromone is covered with a mysterious veil in front of human beings. Although it is generally believed that human sweat glands (especially armpit) can secrete sexual pheromones, such as androsterenone and androsterol, whether we can receive this signal or not has been a controversial topic for a long time. The complexity of human behavior and physiological system makes it more difficult to study. Up to now, no pheromone has been confirmed to have an effect on human body. Such disputes make it more uncertain to speculate that pheromone is playing a role in menstrual synchronization.
To prove that the physiological cycle is related to pheromone, McClintock published a study in 1998. She collected sweat extracts from the armpits of nine women during the follicular (before ovulation) and luteal (after ovulation), and then applied them to the upper lips of 20 women (it is estimated that the 20 girls won a lot of subsidies to come & hellip; & hellip;). The participants were not allowed to wash their faces for six hours, and all other life was the same. Results the sweat in follicular phase made the participants come to the tide ahead of time, while the sweat in luteal phase made the participants delay coming to the tide. Combined with the hormone in follicular phase to promote ovulation and the hormone in luteal phase to inhibit ovulation, McClintock thought that this result proved that the pheromone released in different periods could affect the physiological status of others. However, this conclusion is a little weak. The number of days to advance and postpone the tide (about 2 days) is a little less, even similar to the fluctuation of the length of menstruation - which McClintock himself has to admit.
Question 2: there are many problems in research methods
In 1992, a scientist named h. Wilson published an article, which systematically and detailedly analyzed the problems existing in the research methods of menstrual synchronous research over the years, suggesting that these problems have brought huge errors to the research results and may mislead our recognition of 'McClintock effect' [6].
First of all, he pointed out that previous studies of menstrual synchronization were based on a vague and plausible assumption that the difference was randomly distributed when two women were randomly compared for their diurnal interval. But Wilson calculated that even if you don't do anything, find out the interval between the coming days of menstruation for several women who can't fight with eight poles. Because each person's cycle length is different, about half of them will tend to be synchronized, especially when the number of experimental people is less and the statistical time is shorter. Most studies of menstrual synchronization have the characteristics of small sample size and short duration.
Secondly, when comparing the diurnal interval of incoming tide, how to choose the date will also make the results very different. Suppose that the menstrual cycle length of female a is 28 days, and she comes on the 1st, 29th and 57th day; while the menstrual cycle length of female B is 30 days, and she comes on the 15th, 45th and 75th day. How to judge whether their menstrual cycle tends to be synchronized or separated? If we compare the first and second menstrual periods of female a with that of female B, we will find that the difference between them is 14 days in the first time, and 16 days in the second time, which tends to be separated; if we compare the second and third menstrual periods of female a with that of female B, it will become: the difference between the former one is 14 days, and the latter one is 12 days, Tends to be synchronized. The same data leads to the opposite conclusion, falling into a mathematical trap accidentally.
Moreover, Wilson found that many experiments exclude participants or data that do not conform to the experimental design. Some of the participants in the experiment had irregular menstruation (about 25% according to the statistics), and the number of incoming tides was different from that of others, so the researchers would remove these data during the statistics, which undoubtedly damaged the objectivity of the research.
According to his own analysis of research errors, Wilson analyzed and calculated several representative studies that came to the conclusion of menstrual synchronization one by one, and found that after considering the errors, these research results basically became 'no obvious menstrual synchronization phenomenon'. Wilson also proposed some optimization experiments, such as extending the experiment time and increasing the number of samples.
After Wilson's article was published, the research on the conclusion of menstrual synchronization was greatly reduced, which also showed that his analysis did find out the problem from one side, and provided more careful and rigorous ideas and methods for the later research. After him, there are other problems that may exist in the study of menstrual synchronization. For example, when collecting data, there may be deviation in the way that participants recall the date of coming tide every other period of time; McClintock's 1998 study failed to achieve single blind or double blind when applying sweat extract.
Question 3: what is the meaning of evolution?
The "Whitten effect" of mice was mentioned earlier. Pheromone released by male mice can synchronize the estrus of female mice, which has positive significance for mouse reproduction: when female mice are fully prepared, male mice can "sow widely" at one time, reducing the cost of reproduction. So some people think that the evolutionary significance of menstrual synchronization is similar to this, which provides an explanation for this phenomenon, that is, under the polygamous lifestyle in ancient times, women's menstrual synchronization helps to improve the reproductive efficiency and avoid men 'looking for the wrong person' wasting their physical strength in vain.
But there are also different views. Some researchers think that if there is menstrual synchronization, it is not good for reproduction, because it will cause competition among women, waste part of their fertility, and reduce the reproductive efficiency; and the variety of women's ovulation period can make women more difficult to be controlled by men, so that they have more choice when choosing men, and are more likely to have better offspring [8].
McClintock, who proposed the "McClintock effect", thinks that menstrual synchronization has no effect, but is only an occasional "by-product" in evolution, which is a coincidence. Discussion in the evolutionary sense can promote people's thinking from multiple perspectives, but it can never provide direct evidence for the phenomenon of menstrual synchronization.
There are many controversies about the study of menstrual synchronization, but up to now there is no conclusion. Scientists from both sides have no exact evidence to prove whether there is menstrual synchronization and whether it is related to pheromone. But they all agree that pheromone's research is of great significance to human beings, and this magical thing may open up new senses that human beings have never realized, and open up new areas that we have never explored. It's the right attitude to make a bold guess and then to seek the truth in the cycle of hypothesis building, pushing down and re building.