There are ten manifestations of human sixth sense.

1: I had some dreams, and they really happened.

I have been to a new place and found the scenery there familiar, but I have never set foot here.

3. Before others want to speak, they often know what they want to say.

There is always a normal premonition.

Sometimes the body will feel strange, such as the tingling of skin or internal organs or the feeling of ants crawling.

6. Before the phone rings, it can be predicted that it will ring.

7: I once thought of someone I haven't seen for a long time and met within two days.

8. I once thought of some physiological reactions, such as suffocation and general weakness, and soon disaster happened.

9: I had some colorful dreams.

10: I once heard some unexplained sounds.

The sixth sense of human beings

In foreign countries, human mind or telepathy is called human sixth sense, also known as extrasensory ability (ESP in English). Let's look at the following example. Kiel Igurus, an employee of an advertising company in New Jersey, USA, asked others to cover his eyes with a leather blindfold. He walked15km by bike in the crowded street through telepathy, without encountering any obstacles. Afterwards, Agus said that the secret of his completion of the test was that he received a "decisive wave" from three people who followed. Swan (then 43 years old), an ESP person who was tested at Stanford Research Institute in the United States, is said to be able to see through all parts of the world with an accuracy rate of 90%. With his keen eyes, he drew the secret base of the United States on Diego Garcia Island in the Indian Ocean, which was more accurate than the photos taken by reconnaissance satellites. He also correctly judged the location of the Nike missile base in the United States, which made the military stunned.

Twins should have a strong sixth sense. The sixth sense is not what you feel on purpose, but what you feel inadvertently.

It is generally believed that the word "sixth sense" is roughly consistent with "intuition". But intuition is not only described by the word "thesixthsense", but also includes premonition, inspiration, epiphany, inner voice or premonition. Personally, I think "intuition" and "sixth sense" can better represent the explanation of this problem by modern psychology. Intuition refers to the feeling that does not use the five senses reflex, and the two words "sixth sense" and "subconscious" are the same in definition method, both of which are a set of definitions of exclusion.

Western psychologists believe that consciousness receives external stimuli through five senses: hearing, sight, taste, smell and touch, and then sorts out and analyzes them, and finally recognizes them. The subconscious will accept more things that are missing from the conscious level, which are not obtained through language or logical reasoning. This information has been stored in our brains for many years and we have never noticed it. When they emerge to the level of consciousness and become recognizable feelings, they are what we call "intuition" and "sixth sense"

In other words, the sixth sense is a floating object in the subconscious, which can be recognized by the consciousness.

The first five senses are sight, hearing, smell, taste and touch.

Looking for the sixth sense of human beings

As we all know, human senses are divided into five kinds in physiology: sight, hearing, smell, taste and touch. At the molecular level, this division is unreasonable. Our sense of external stimuli is realized through protein, which is called receptor. Vision is unique, it senses light stimulation through photoreceptors, but hearing and touch are actually the same, both of which sense mechanical stimulation through mechanical receptors. Smell and taste are the same kind. They have chemoreceptors and feel chemical molecules, but smell feels gas molecules and taste feels liquid molecules. So these five senses are actually three. In addition, our body has other senses, such as pain receptors, temperature receptors, osmotic pressure receptors and so on. These feelings do not form special sensory organs, which are not counted.

There is also a sixth sense in the animal kingdom: the feeling of foreign hormones. Exohormone is a chemical substance secreted by animals, which is used to influence the behavior of similar animals (usually only for one sex). From unicellular protozoa, insects to mammals, pheromones are used to communicate with each other. Moths use pheromones to find mates, ants use pheromones to regulate social behavior and mark food clues, and mammals use pheromones to mark territory, issue warnings and find mates. In mammals, pheromones are excreted together with urine, sweat and sexual secretions, and quickly evaporate and spread. The organ that feels pheromones is called vomeronasal organ, which is a cartilage structure located at the bottom of nasal septum. Although its receptor is located in the nasal cavity, it feels and smells different to pheromones. Olfactory receptors are located in the nasal mucosa, and about 1000 chemical receptors are connected with olfactory neurons. It senses gas chemical molecules, and the generated neural signals are transmitted to the olfactory bulb above the nasal cavity, and then to the olfactory region of the cerebral cortex for processing, causing complex physiological and psychological reactions, which are almost consciously felt and often evoke memories. The chemical receptors of pheromones are a special kind of cell surface receptors, which are much less than olfactory receptors. Unlike olfactory neurons, pheromone neurons have no flagella. They can't feel gas chemical molecules, only liquid molecules. Many pheromones in mammals are protein macromolecules, which are difficult to volatilize. Even if it is spread through the air, it exists in the form of liquid, and some pheromones reach the vomeronasal organ through the mouth (such as licking each other). The role of pheromones and receptors in the body is similar to that of hormones and receptors, and the transmission pathway of neural signals produced by pheromones is also different from that of smell. It first passes to the "accessory olfactory bulb" and then reaches the hypothalamus and pituitary gland, which control the secretion of hormones (especially sex hormones). The feeling of foreign hormones is completely subconscious. It has no taste, does not evoke memories, and its reaction has nothing to do with previous experiences. It leads to an evolutionary instinctive reaction.

Our understanding of the role of mammalian pheromones is mainly through experiments on mice. In one experiment, mice in cages were placed in a tense environment for several days, and then they were taken out and moved to another room. The original cage was not cleaned (in order to keep the residual pheromones), and the mice that had been leisurely in a quiet environment were put in. Half an hour later, these mice became as nervous as the previous mice. Blood tests showed that a lot of hormones were secreted in the blood to cope with the tense environment. Obviously, these hormones are secreted under the stimulation of pheromones left by old tenants.

Exohormone can not only be used for emotional communication, but more importantly, it can affect reproductive activities. Under normal circumstances, female rats will be in estrus once every five or six days, that is, ovulation, so that male rats can mate. If there are too many female rats in a cage, the estrus (ovulation) of female rats will be inhibited. However, if the vomeronasal organ of one female rat is removed, she will have a normal estrus cycle, which indicates that the inhibition of estrus is caused by pheromones secreted by other female rats. For those female rats whose estrus is inhibited, if they smell the urine excreted by male rats, the inhibition will be lifted. Those female rats in normal estrus will be in estrus ahead of schedule after smelling the urine of male rats or even protein extracted from urine, and those "virgin rats" who have never been in estrus will also be in estrus for the first time ahead of schedule. However, if the vomeronasal organ of the female rat is removed, the urine of the male rat can no longer play a role, indicating that this effect is also caused by pheromones. Similarly, the pheromone of female mice will also have an impact on male mice, stimulating male mice to secrete male hormones, leading to a series of reproductive behaviors. If the vomeronasal organ of male rats is removed, they are no longer interested in female rats and are unwilling to mate.

Can a similar experiment be done at the molecular level, that is, only one gene related to pheromone communication is removed without removing the whole vomeronasal organ? In the nose plough, there is a kind of protein called TRP2, which is considered to be related to the transmission of pheromone signals. Recently, researchers at Harvard University "knocked out" the gene that produces this protein from male mice. Such male mice no longer produce TRP2 protein and cannot accept the stimulation of foreign hormones, which is expected to make male mice lose interest in mating. However, the "knockout" mice can mate normally when they are put together with estrus females, which is beyond the expectation of the researchers and makes them very disappointed. They further studied whether there were other abnormalities in the behavior of these "knockout" male mice. After keeping a male mouse in a cage for a period of time, it takes this cage as its own territory. If it is put into other male mice, it will be attacked. This aggressive behavior is also caused by the stimulation of pheromones. However, when the male mouse was put into the cage where the male mouse was knocked out, the male mouse lost its aggressiveness. Strangely, it tried to mate with the new male mouse. If the female mouse and the male mouse are put in at the same time, the "knocked out" male mouse will try to mate with them indiscriminately. These male mice without TRP2 gene became docile and excited bisexual mice: making love instead of making war. (Published in American Science Journal on February 22, 2002)

The role of pheromones is also related to genetic differences. This involves a large class of genes called histocompatibility genes. It is named because it is found that immune rejection is not easy to occur when organ transplantation is performed between two individuals with the same or similar genes. There are many sets of mouse histocompatibility genes called H-2 genes. In one experiment, researchers bred a group of mice. They have exactly the same gene, only H-2 gene has two kinds. When mating them, the researchers found an unexpected strange phenomenon. Male mice tend to mate with female mice with different H-2 genes. A simple experiment can prove that this is related to pheromones. In the two rooms of the rat nest, the urine of two kinds of female rats (one with the same H-2 gene and the other with different H-2 gene) was sprinkled, and the male rats were put in. Nine times out of ten, they will go to the room where female rats with different H-2 genes pee. If the urine of two kinds of male rats is spilled in the room, the probability of male rats choosing the room is the same. On the contrary, if a female mouse is given a choice, she will also tend to choose a male mouse with different H-2 genes. Because the other genes of these mice are exactly the same, it shows that this preference for spouses is completely caused by the difference of H-2 genes. The histocompatibility gene is regarded as a symbol of an individual, and animals tend to mate with the opposite sex, which can be regarded as an instinctive behavior to prevent inbreeding.

Humans also have histocompatibility genes, called HLA genes. Like mice, HLA genes seem to be related to human mate selection. In an isolated community in South Dakota, the researchers investigated the HLA gene distribution of its members. The members of the community are basically descendants of early immigrants, and there are few immigrants, so there are relatively few HLA alleles. After taking blood samples to detect HLA genes, it is found that young people tend to marry people with different HLA genes and avoid people with the same HLA genes. 1994, several Swiss zoologists made a more direct experiment. They found a group of men and asked them to take a bath with tasteless soap on Sunday night, then put on their shirts for two consecutive nights and handed them in on Tuesday morning. The researchers put the shirts in a cardboard box and covered them with a small hole, so that women in the middle of their menstrual cycle (when they have the most sensitive sense of smell) could smell the shirts and record their feelings. Each woman has seven samples, one is a clean shirt, three are worn by men with similar HLA genes, and the other three are worn by men with very different HLA genes. The results show that women like or even revel in the body odor of men whose HLA genes are quite different from their own, but hate men whose HLA genes are similar to their own. Interestingly, for those women who take birth control pills (the hormone level in the body is similar to that of pregnant women), the result is just the opposite. In addition, the body odor of men with different HLA genes often reminds women of their current or former spouses. 1997, this research group did experiments on both men and women. They showed 12 1 men and women six shirts, two of which were worn by women and four by men. Then ask them to rate the taste of shirts. This experiment shows that the subjects dislike the body odor of people with similar HLA genes, but they only slightly dislike or care about the body odor of people with different HLA genes, which often reminds them of their spouses or ex-spouses. Interestingly, this preference is only related to HLA genes, but not to gender: one man scored the highest on the taste of the shirt worn by another man in this experiment.

Rats obviously use pheromones to convey the information of histocompatibility gene differences, while humans may use ordinary body odor. It is difficult to confirm whether pheromones also play a role in human mate selection. In fact, biologists have always denied that humans have pheromones. Until 197 1, psychologist Martha of Harvard University (now University of Chicago)? The research published by Martha McClintock makes the academic circles take human beings seriously for the first time, and they may unconsciously use pheromones to transmit signals.

There has always been a folk saying that the menstrual cycle of cohabiting women will become synchronous, but this statement has not been confirmed. Mcclintock made a serious study of this. She made a survey of 135 female college students in a university dormitory, and found that the menstrual cycles of people living in the same dormitory (physically close) and close friends (psychologically close) are synchronized, and those who are both roommates and friends have the best synchronization. Later, other researchers repeated similar surveys, and although exceptions were found (for example, the menstrual cycle of women taking birth control pills was determined by estrogen in birth control pills and would not be synchronized with others), most of them confirmed mcclintock's results. The menstrual cycle is influenced by environmental factors. These female college students all live in similar environments. Will this lead to menstrual synchronization? Mcclintock ruled out this possibility because those female college students who live in the same dormitory at the same time, but are neither roommates nor friends, have irregular menstruation. It is also possible that these roommates or friends keep the menstrual cycle synchronized through subtle social interaction. Roommates or friends generally know each other's menstruation, and it is possible to control menstruation subconsciously by obtaining this information. This possibility is hard to rule out. However, mcclintock advocates the third possibility, that is, these female college students influence their menstrual cycle through pheromones.

To prove this idea, mcclintock first experimented with mice. If the females are kept in the same cage, their estrus will be synchronized. Mcclintock kept two groups of female rats in two cages, and connected them with ventilation pipes to let the wind blow from one cage to the other. She found that if the female rats in the upper tuyere cage were raised before estrus, the estrus cycle of the female rats in the lower tuyere cage would be prolonged; If the female rats are kept in the upper draught cage after estrus, the estrus cycle of the female rats in the lower draught cage will be shortened. Therefore, mcclintock thinks that the synchronization of estrous cycle in female rats is coordinated by two pheromones with opposite effects. 1998, mcclintock conducted a similar experiment on people. Her research subjects are 29 young women between the ages of 20 and 35. These women can't take birth control pills, and 9 of them bathe with tasteless soap every day. After taking a bath, they put a cotton pad under their armpits to collect secretions. Mcclintock speculated that human armpits secrete pheromones, because those mammals who know that they can communicate with pheromones have glands secreting pheromones under their armpits. When women reach puberty, they will start to secrete obvious body odor, indicating that chemical changes related to reproduction have taken place. Put the cotton pad under your armpit for 8 hours, collect it and cut it into small pieces. Let the other 20 women wipe their noses with cotton pads in the morning, and don't wash the painted places for 6 hours. This experiment has been done for two months, and the results are the same as those found in the experiment of female mice: the axillary substances collected from women before ovulation (equivalent to the "pre-estrus" of female mice) will advance the ovulation date of all recipients and shorten the menstrual cycle, while the axillary substances collected from women who have just ovulated will delay the ovulation date and prolong the menstrual cycle. Because I just took a bath before collection, these underarm substances have no detectable taste, so the general body odor is unlikely to play a role, just some tasteless chemical components. Its function is similar to that of female mice, indicating that it may also be a pheromone.

In 2000, mcclintock announced that pheromones can not only regulate people's physiological state, but also affect people's psychological state. She tested two steroids secreted by the human body: androsterone secreted by men and estrine secreted by women. These two hormones are tasteless, but they are often added to perfume for women and cologne for men, which are considered to attract men and women respectively. Mcclintock's team asked 65,438+00 men and 65,438+00 women to dilute these two steroids with propylene glycol and apply them under their noses and necks. As a control, the same place was coated with propylene glycol without steroids. Then, the researchers conducted a series of psychological tests on the subjects to compare the effects of these chemicals on their thinking and psychological state. Subjects entered the laboratory to answer the questionnaire. After a period of time, after the excitement of participating in the experiment, they will be depressed and even angry. But for those women who have used steroids, whether they use androstenedione or estrone, they can maintain a good psychological state from beginning to end. Steroids have the opposite effect on men, and the mood becomes worse after painting. After six minutes of exposure to steroids, the psychological state of the subjects will change. 200 1 mcclintock Laboratory provides direct evidence that steroids affect human brain function. They found that after inhaling androstenedione, the utilization rate of blood sugar in subcortical and neocortical areas of the brain changed widely. These areas are not dedicated to the sense of smell, and their changing patterns are similar to those of chemicals that can affect the psychological state. This shows that chemicals can change the metabolism and function of the brain even if they are not consciously detected.

Before mcclintock recently announced this series of discoveries, many people announced the discovery and extraction of human sex pheromones, and put the extracts and compounds on the market. However, due to the strong commercial motives of these studies, their reliability has always been doubted. Mcclintock laboratory provided more direct and reliable evidence, but the controversy did not subside. Androstenedione and estrone can be detected in human blood, but we don't know whether they are distributed to the outside world, let alone whether they really play a role in daily life. Even if the human body is releasing pheromones, we can't be sure how they are accepted by others. Unlike other mammals, human vomeronasal organ is highly degraded. In fetuses and newborns, there is obviously a vomeronasal structure. Newborns, like the offspring of other mammals, seem to be able to find their breasts through pheromones from their mothers' nipples. But as the baby grows up, the vomeronasal organ gradually degenerates. The anatomy of 564 adults shows that 70% of them do not have the structure of vomeronasal organ, and the remaining 30% of vomeronasal organ is also highly degraded. No neurons were found in adult vomeronasal organ, and no vomeronasal nerve was found to transmit signals. Therefore, it is impossible for the adult vomeronasal organ to have a function. So, if pheromones can affect the behavior of adults, how do they enter the body and transmit nerve signals? Studies on rabbits and pigs show that pheromones can also transmit signals through olfactory tissues. In August 2000, researchers from Rockefeller University and Yale University jointly published a paper. According to this study, receptors for detecting human pheromones seem to exist in olfactory cells. It is known that there are 100 pheromone receptor genes in rats. Based on the sequences of these genes, the researchers searched the human genome sequence to see if there were gene sequences similar to pheromone receptors. They found eight similar human gene sequences, but seven of them are nonfunctional "pseudogenes" and only 1 is a true gene. The gene named V 1RL 1 codes for protein, which mainly exists in human nasal mucosa. The genes of 1 1 population of different nationalities were detected, and it was found that there were two V 1RL 1 genes with slightly different structures. There may be other genes similar to pheromone receptors in humans, but it is unlikely that there are many. Whether this receptor really plays a role in detecting pheromones in human body needs further study.

Of course, human behavior is not determined by any single factor. People's mate selection, courtship, sexual behavior and reproductive behavior are all influenced by countless physiological, psychological and social factors. Even if only physiological factors are considered, almost all senses are involved at the same time. The unparalleled human cerebral cortex enables us to process and synthesize information from multiple senses at the same time, rather than being manipulated by only one sense. Therefore, it is certain that even if pheromones can affect human behavior, they will never play a decisive role as they do in other mammals. The process of searching for human sixth sense just makes us further understand the complexity of human behavior, and some factors affecting it are as elusive as pheromones.

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Originally published in the fifth issue of Science Illustrated in 2002.