The "one-sex/two-sex" theory claims that the switch from the one-sex model to the two-sex model created the foundations of gender as we know them today. [ 14 ]  The explanations for this shift are both epistemological and political. [ 15 ]  In terms of the epistemological, in the beginning of the eighteenth century, experts with authority were determining what was natural and what was not. [ 15 ]   Michel de Montaigne , a writer during the French Renaissance, writes in his  Travel Journal , about a group of young girls who dressed up like males and led their lives as males. For him, this was seen as perfectly normal and that "there is no ontological sex, only organs assigned legal and social status". [ 16 ]  In the two-sex model though, these experts wanted to create a link between biological sex and theoretical gender and anything transgressing these boundaries was seen as being abnormal. [ 15 ]  Although it was thought in the one-sex model that  feminine men  may lactate and that "almost all the men have a great quantity of milk in their breasts", [ 17 ]  the notion of interconvertibility of fluids among men and women was thrown out the window in the two-sex model. Sex became related to physical facts and the uterus became a justification for the status of women. [ 18 ]  Gender roles became institutionalized and what was meant to be male or female was based on what the experts thought was natural. [ 18 ]  Philosophers like  Rousseau  supported this view and he saw women as being relegated to the private sphere as wives and mothers while men dominated the public sphere. [ 19 ]


The "one-sex/two-sex" theory also sees politics as helping to bring about the dominance of the two-sex model. There were endless struggles for power and position occurring between and among men and women. [ 18 ]  In order to have power over women, men would use sexual anatomy and sexual differences to support their superiority. [ 18 ]  The subordination of women by men began with the hierarchical ordering of their bodies and ended with their firmly defined gender roles. Thus, "women's protected and conservative role in the household and society was justified by arguments preordained function." [ 20 ]  Sex was seen as being a major battleground during the French Revolution and "the creation of a bourgeois public sphere...raised with a vengeance the question of which sex(es) ought legitimately to occupy it." [ 21 ]  Articulate men were the ones who brought about biological evidence to support the notion that women were "unfit for the chimerical spaces that the revolution had inadvertently opened" [ 21 ]  and thus propagated the notion that women were inferior to men.


Renaissance anatomical illustrations depicted a woman as a man turned inside out. Male and female organs were often depicted side by side to demonstrate their correspondence to one another. Anatomist and physician  Andreas Vesalius , represented women's organs as versions of man's in all three of his influential works. [ 22 ]  The vagina was often depicted as long, phallic and almost indistinguishable from a penis. Representation of the anatomical difference between men and women were independent of the actual structures of these organs and "ideology, not accuracy of observation, determined how they were seen and which differences would matter." [ 23 ]  Often, the only way to distinguish a female set of organs from a male set of organs would be if the illustrator were to cut away the front of what appears to be a womb in his drawing to reveal a child inside. This is because "the more Renaissance anatomists dissected, looked into and visually represented the female body, the more powerfully and convincingly they saw it to be a version of the males" [ 24 ]


Physiologically, the one-sex model explains that "in the blood, semen, milk and other fluids of the one-sex body, there is no female and no sharp boundary between the sexes". [ 25 ]  Different levels of each of the fluids are what would determine gender. The body was also seen as composed of four humours: cold, hot, moist, and dry. Just as with fluid composition, individuals varied in the humoral composition as well. "Though women were always dominated by cold and moist humours, and men by hot and dry humours, difference in sex were seen as differences of degree." [ 26 ]  In terms of reproduction in the one-sex model, the sex of the child produced by a couple was based on the intermixing of the fluid of a couple. Laqueur discusses the interconvertibility of bodily fluids as a feature of the one-sex model. [ 27 ]  In particular, he considers various early theories of reproductive fluids by Aristotle, Hippocrates, Galen, and  Avicenna .


Aristotle claims the existence of one seed, such that both male and female reproductive fluids originate from blood. [ 28 ]  However, male sperm is more refined and powerful than its female counterpart. [ 28 ]  The only distinction between reproductive fluids in this one-seed model is their hierarchy. [ 28 ]  Hence “the male and female seed cannot be imagined as sexually specific, morphologically distinct, entities”. [ 28 ]  In Aristotle's more metaphysical conception, male ejaculate carries the “efficient cause” that acts on the female generative material to bring about conception. [ 29 ]


According to Laqueur, the Hippocratic model of sperm interaction is not strictly hierarchized on sex like in Aristotle's explanation. [ 30 ]  In this model, sometimes women may produce stronger seed, and men may produce weaker seed. [ 30 ]  Both quantity and strength of sperm matters: male offspring is generated by strong sperm from both parents, while female offspring is generated by weak sperm from both parents, but in the case that strong and weak sperm are both involved, the offspring's sex depends on the sperm of greater quantity. [ 30 ]


Galen's model of sperm interaction ranks male seed above female seed in quality. [ 31 ]  Laqueur explains that Galen considered women's seed to be true semen of inferior quality to male semen because women have less internal heat than men and are thus are less “perfect”. [ 31 ]  The same perfect vs. lesser relationship is present between male and female reproductive fluids as in Galen's model as male and female genitalia. [ 31 ]  Laqueur expands this discussion through Avicenna's argument that female seed and menstrual blood are less refined forms of blood, while male seed is a more refined form of blood. [ 32 ]


The idea of a woman having to have an  orgasm  in order to conceive was prevalent in the one-sex model, especially as it aligns with the interconvertibility of bodily fluids in the one-sex model. [ 33 ]  It was thought by people such as Galen that in order for a woman to get pregnant, she must have an orgasm. [ 34 ]  When a woman would reach an orgasm, the mouth of her womb would open and suck up the male ejaculate like a sponge. [ 35 ]  It was thought that both males and females experience an orgasm during intercourse and that both released some sort of fluid, which would mix together and the two emissions would result in conception. [ 36 ]  Galen and Aristotle point out similarities between male and female genitalia in relation to orgasm: both the penis and the neck of the uterus are areas filled with nerves, and both male and female emissions stimulate the sexual organs. [ 37 ]  Laqueur also references Avicenna's similar comparison that the flesh of both sexes is brought to arousal by the emission of fluids. [ 35 ]  Under the economy of bodily fluids, the presence of both male and female seed and orgasms points to a sexless conception of libido that fits in a one-sex model. [ 37 ]


The observation that women have organs that resemble those of men and experience orgasms as men do would seem to assign them an equally active role in conception as men. [ 38 ]  Women needed to orgasm to produce fluids during intercourse that would stir with the male ejaculate to conceive a child. [ 36 ]  Laqueur notes that "the fact that women had gonads like men, that they had sexual desires, that they generally produced fluid during intercourse and presumably showed signs of 'delight and concussion', all confirmed the orgasm/conception link." [ 33 ]  In Laqueur's one-sex model, the exception to this orgasm-conception link is Aristotle, who sought to separate orgasm from conception to preserve his asymmetrical view of men as providing the "efficient cause" and women the "material cause" during generation. [ 39 ]


As opposed to the one-sex model, the two-sex model held that a woman could conceive without an orgasm. [ 40 ]  At the beginning of  Making Sex , Laqueur relates the anecdote of a beautiful young woman who was in a deathlike coma. She was raped by a young monk and conceived a child. [ 41 ]  This story challenges the one-sex notion that a woman needs to experience an orgasm in order to conceive. [ 40 ]  By saying that conception was not related to orgasm, sexual pleasure for women seemed to lose importance. [ 42 ]  Further, Laqueur claims that this newfound absence of the female orgasm during conception motivated a new relationship between male and female bodies. [ 43 ]  When in the eighteenth century it became a possibility that "the majority of women are not much troubled with sexual feelings, the presence of or absence of orgasm became a biological signpost of sexual difference." [ 42 ]  Whereas orgasm was seen as a shared phenomenon between sexes under Laqueur's one-sex model, he proposes that the irrelevance of the female orgasm after the eighteenth century became a determinant of female anatomical and sexual difference. [ 40 ]  Women were to be seen as passionless and not enjoying sex. [ 40 ]


It was also thought prior to the eighteenth century that ovulation corresponded to sexual intercourse. [ 44 ]  Biologists at this time had very little knowledge of what actually governed the production of an egg. [ 45 ]  However, Laqueur claims that scientific advances in the eighteenth century had little to do with the declining importance of the female orgasm to conception, or more generally, with the shift to the two-sex model. [ 46 ]  Because sexual difference is already laden with cultural constructs, Laqueur writes that "the nature of sexual difference is not susceptible to empirical testing." [ 47 ]  Rather, he proposes that political and social changes ignited the interest in searching for anatomical differences between men and women. [ 48 ]


According to Laqueur, the declining importance of the female orgasm during conception cannot be attributed to a lack of knowledge about female genitalia either. [ 49 ]  There was biological evidence around the nineteenth century that parts of the female anatomy, specifically the clitoris "contributes "a large share, and perhaps the greater part, of the gratification which the female derives from sexual intercourse."" [ 49 ]  However, one 1836 handbook that Laqueur references also claims that women could experience orgasms without physically feeling them. [ 49 ]  Laqueur uses this example to explain that female anatomy and sexuality are defined according to "the demands of culture." [ 49 ]  He concludes that it was "culture and not biology that was the basis for claims bearing on the role and even the existence of female pleasure. The body shifted easily in the eighteenth century from its supposedly foundational role to become not the cause but the sign of gender." [ 50 ]


The change from the one-sex model to the two-sex model helped to create a new understanding of gender in the meaning of human history. There is an "increasing differentiation of male and female social roles; conversely, a greater differentiation of roles and a greater female 'delicacy and sensibility' are [seen as] signs of moral progress." [ 51 ]  If men and women are seen as being physically different, then they must be treated differently as well.


In the two-sex model, since there are physical differences between men and women, there must be differences in how they receive pleasure.  Sigmund Freud  tries to explain the functions of the clitoris by challenging the preconceived notions about it. Freud feels that "if we are to understand how a little girl turns into a woman, we must further follow the vicissitudes of [the] excitability of the clitoris." [ 52 ]  He sees the clitoris as being "the organ through which excitement is transmitted to the 'adjacent female sexual parts' to its permanent home, the true locus of a woman's erotic life, the vagina." [ 53 ]  For Freud he uses the analogy of the clitoris as "pine shavings [used to] set a log of harder wood on fire". [ 53 ]  For Freud, there is no real female interior if pleasure can transfer from the clitoris to the vagina. Freud tries to provide evidence for a vaginal orgasm and he makes it so a clitoral orgasm is seen to be adolescence. By downplaying the role of the clitoris, he makes women's sexual needs seen as being inferior and secondary to those of men. He says that "whenever a woman is incapable of achieving an orgasm via coitus, provided the husband is an adequate partner, and prefers clitoral stimulation to any other form of sexual activity, she can be regarded as suffering from frigidity and requires psychiatric assistance." [ 54 ]  In the two-sex model, it is seen that Freud "must be regarded as a narrative of culture in anatomical disguise. The tale of the clitoris is a parable of culture, of how the body is forged into a shape valuable to civilization despite, not because of itself". [ 55 ]  Freud changed the meaning of the clitoris and contributes to the notion of the passionless woman.


Laqueur says that there was obvious evidence around in Freud's time that the clitoris was in fact the source of pleasure in women.  François Mauriceau  notes that the clitoris is "where the author of Nature has placed the seat of voluptuousness – as he has in the glans of the penis – where the most exquisite sensibility is located, and where he placed the origins of lasciviousness in women." [ 56 ]  The vagina on the other hand was seen as "a far duller organ" and "only the glands near its outer end are relevant to sexual pleasure because they pour out great quantities of a saline liquor during coitus, which increases the heat and enjoyment of women". [ 57 ]  By changing the meaning of the clitoral orgasm, Freud seems to be putting women in opposition to men and further assigning women to socially assigned roles. To say that a woman is supposed to orgasm through her vagina as opposed to her clitoris "works against the organic structures of the body." [ 58 ]  In Laqueur's "one-sex/two-sex" theory, he sees Freud as being instrumental in the sexual socialization of women. He feels that "the cultural myth of vaginal orgasm is told in the language of science. And thus, not thanks to but in spite of neurology, a girl becomes the Viennese bourgeois ideal of a woman." [ 58 ]


Scholars such as  Katharine Park , Robert Nye,  Helen King ,  Joan Cadden , and Michael Stolberg have criticized Laqueur's theory on the grounds that his described shift from one-sex to two-sex does not reflect a thorough reading of historical sources.


According to Park and Nye, Laqueur synthesizes conflicting accounts of sex and anatomy by Aristotle and Galen in order to craft the impression of a uniformly accepted one-sex model prior to the eighteenth century. [ 59 ]  In Park and Nye's account, Laqueur mistakenly takes early anatomists' comparisons between male and female genitalia as evidence that, in their view, “the vagina really is a penis, and the uterus is a scrotum.” [ 60 ] [ 61 ]  Park and Nye also remark that Laqueur does not locate the historical evidence he uses within culturally and historically specific definitions of sex; instead, he uses it out of context to fit a modern understanding of sex and gender. [ 62 ]  In particular, Laqueur reduces the metaphysical distinctions Renaissance philosophers made between men and women to sociological categories of gender, while still maintaining that there must have only been one anatomical sex. [ 62 ]


King echoes Park and Nye in the claim that the one-sex and two-sex models seem to have coexisted throughout history, and were not segregated by era as Laqueur suggests. [ 63 ]  King argues that the one-sex and two-sex models, on paper, could be a useful tool of historical enquiry but they have not been read that way. She writes that the theories in  Making Sex  are appealing because Laqueur conceptualizes a simple chronological narrative of his one-sex and two-sex models, even at the cost of historical context and nuance. [ 64 ]  For instance, Laqueur omits sections of his pre-eighteenth century sources that portray men and woman in a balanced one-sex model due to their reciprocal anatomy, instead proposing a one-sex model that centers male anatomy and defines female anatomy as the inverse. [ 64 ]  The use of these models creates a static perception of the period, damaged by arbitrary divisions of 'before' and 'after' that were not relevant to people at the time. [ 65 ] : ix–xi


Stolberg provides evidence to suggest that significant two-sex understandings of anatomy existed before Laqueur claims, arguing that sexual dimorphism was accepted as early as the sixteenth century. [ 66 ] : 276   He discusses the influence of the uterus on medical discussion as proof that understandings of the body were noticeably 'sexed' in the 1600s. He also argues that differences between the sexes were accepted in the early modern period under the proviso that woman's biology was fit for purpose, i.e., motherhood. [ 66 ] : 298   Further, Stolberg contests Laqueur's claim that sexual dimorphism arose merely in response to Enlightenment ideals of equality, as a means of keeping women insubordinate. [ 67 ]  He cites a complex network of other reasons for the shift to sexual dimorphism. These include a renewed emphasis on empirical observation during the sixteenth and seventeenth centuries as well as a shift away from  humorism . [ 67 ]


Joan Cadden has pointed out that 'one-sex' models of the body were already treated with scepticism in the ancient and medieval periods, and that Laqueur's periodisation of the shift from one-sex to two-sex was not as clear-cut as he made it out to be. [ 68 ]


Orgasm  (from  Greek   ὀργασμός ,  orgasmos ; "excitement, swelling") or  sexual climax  (or simply  climax ) is the sudden release of accumulated  sexual excitement  during the  sexual response cycle , characterized by intense sexual  pleasure  resulting in rhythmic, involuntary  muscular contractions  in the  pelvic  region. [ 1 ] [ 2 ]  Orgasms are controlled by the involuntary or  autonomic nervous system  and experienced by both males and females; the body's response includes muscular  spasms  (in multiple areas), a general  euphoric  sensation, and, frequently, body movements and vocalizations. [ 2 ]  The period after orgasm (known as the  resolution phase ) is typically a  relaxing experience  after the release of the  neurohormones   oxytocin  and  prolactin , as well as  endorphins  (or "endogenous  morphine "). [ 3 ]


Human orgasms usually result from physical  sexual stimulation  of the  penis  in males (typically accompanied by  ejaculation ) and of the  clitoris  (and  vagina ) in females. [ 2 ] [ 4 ] [ 5 ]  Sexual stimulation can be by  masturbation  or with a  sexual partner  ( penetrative sex ,  non-penetrative sex , or other  sexual activity ). Physical stimulation is not requisite though, as possibilities exist to reach orgasm through psychological means alone. [ 6 ]  And getting to orgasm may be difficult without a suitable  psychological state . During sleep, a  sex dream  can trigger an orgasm and the release of sexual fluids.


The health effects surrounding the human orgasm are diverse. There are many physiological responses during sexual activity, including a relaxed state, as well as changes in the  central nervous system , such as a temporary decrease in the  metabolic  activity of large parts of the  cerebral cortex  while there is no change or increased metabolic activity in the  limbic  (i.e., "bordering") areas of the brain. [ 7 ]  These effects affect cultural views of orgasm, such as the beliefs that orgasm (and the frequency or consistency of it) is either important or irrelevant for satisfaction in a  sexual relationship , [ 8 ]  and theories about the biological and evolutionary functions of orgasm. [ 9 ] [ 10 ]  There are also  sexual dysfunctions  involving orgasm, such as  anorgasmia .


In a clinical context, orgasm is usually defined strictly by the  muscular contractions  involved during  sexual activity , along with the characteristic patterns of change in  heart rate ,  blood pressure , and often  respiration rate  and depth. [ 11 ]  This is categorized as the sudden discharge of accumulated sexual tension during the  sexual response cycle , resulting in rhythmic muscular contractions in the  pelvic  region. [ 1 ] [ 2 ]  Definitions of orgasm vary, [ 12 ]  and at least 26 definitions of orgasm are listed in the 2001 journal  Clinical Psychology Review . [ 13 ]


There is some debate about whether certain types of sexual sensations should be accurately classified as orgasms, including female orgasms caused by  G-spot  stimulation alone, and the demonstration of extended or continuous orgasms lasting several minutes or even an hour. [ 14 ]  The question centers around the clinical definition of orgasm, but this way of viewing orgasm is merely physiological, while there are also psychological, endocrinological, and neurological definitions of orgasm. [ 12 ] [ 13 ] [ 15 ]  In these and similar cases, the sensations experienced are subjective and do not necessarily involve the involuntary contractions characteristic of orgasm. In both sexes, they are extremely pleasurable and often felt throughout the body, causing a mental state that is often described as transcendental, and with  vasocongestion  and associated pleasure comparable to that of a full-contractionary orgasm. For example, modern findings support the distinction between ejaculation and male orgasm. [ 2 ] [ 13 ]  For this reason, there are views on both sides as to whether these can be accurately defined as orgasms. [ 15 ]


Orgasms can be achieved during a variety of activities, including  vaginal ,  anal ,  oral ,  manual ,  non-penetrative sex , or  masturbation . They may also be achieved by the use of a  sex toy  or an  erotic electrostimulation . Achieving orgasm by stimulation of the  nipples  or other  erogenous zones  is rarer. [ 16 ] [ 17 ]  Multiple orgasms are also possible, especially in women, but they are also uncommon. [ 2 ] [ 18 ]  Multiple orgasms are orgasms that occur within a short period of one another. [ 18 ]


In addition to physical stimulation, orgasm can be achieved from psychological arousal alone, such as during dreaming ( nocturnal emission  for males or females) [ 13 ] [ 15 ] [ 19 ]  or by  forced orgasm . Orgasm by psychological stimulation alone was first reported among people who had  spinal cord injury . [ 19 ]  Although sexual function and  sexuality after spinal cord injury  are very often impacted, this injury does not deprive one of the sexual feelings such as  sexual arousal  and erotic desires. [ 19 ]


Scientific literature focuses on the psychology of female orgasm significantly more than it does on the psychology of male orgasm, which "appears to reflect the assumption that female orgasm is psychologically more complex than male orgasm," but "the limited empirical evidence available suggests that male and female orgasm may bear more similarities than differences. In one controlled study by Vance and Wagner (1976), independent raters could not differentiate written descriptions of male versus female orgasm experiences". [ 15 ]


In women, the most common way to achieve orgasm is by direct sexual stimulation of the  clitoris  (meaning consistent  digital ,  oral , or other concentrated friction against the external parts of the clitoris). General statistics indicate that 70–80 percent of women require direct clitoral stimulation to achieve orgasm, [ 2 ] [ 20 ] [ 21 ]  although indirect clitoral stimulation (for example, via  vaginal  penetration) may also be sufficient. [ 5 ] [ 22 ]  The  Mayo Clinic  states, "Orgasms vary in intensity, and women vary in the frequency of their orgasms and the amount of stimulation necessary to trigger an orgasm." [ 23 ]  Clitoral orgasms are easier to achieve because the  glans of the clitoris , or clitoris as a whole, has more than 8,000 sensory  nerve  endings, which is as many (or more in some cases) nerve endings as are present in the human penis or  glans penis . [ 24 ] [ 25 ] [ 26 ]  As the clitoris is  homologous  to the penis, it is the equivalent in its capacity to receive sexual stimulation. [ 27 ] [ 28 ]


One misconception, particularly in older research publications, is that the vagina is completely insensitive. [ 29 ]  In reality, there are areas in the anterior vaginal wall and between the top junction of the  labia minora  and the  urethra  that are especially sensitive. [ 30 ]  With regard to specific density of nerve endings, while the area commonly described as the  G-spot  may produce an orgasm, [ 2 ] [ 31 ]  and the  urethral sponge  (area in which the G-spot may be found) runs along the "roof" of the vagina and can create pleasurable sensations when stimulated, intense sexual pleasure (including orgasm) from vaginal stimulation is occasional or otherwise absent because the vagina has significantly fewer nerve endings than the clitoris. [ 4 ] [ 32 ] [ 33 ]  The greatest concentration of vaginal nerve endings are at the lower third (near the entrance) of the vagina. [ 2 ] [ 4 ] [ 34 ] [ 35 ]


Sex educator  Rebecca Chalker states that only one part of the clitoris, the urethral sponge, is in contact with the penis, fingers, or a  dildo  in the vagina. [ 36 ]  Hite and Chalker state that the tip of the clitoris and the inner lips, which are also very sensitive, are not receiving direct stimulation during penetrative intercourse. [ 36 ] [ 37 ]  Because of this, some couples may engage in the  woman on top position  or the  coital alignment technique  to maximize clitoral stimulation. [ 38 ] [ 39 ]  For some women, the clitoris is very sensitive after climax, making additional stimulation initially painful. [ 40 ]


Masters and Johnson  argue that all women are potentially multiply orgasmic, but that multiply orgasmic men are rare, and stated that "the female is capable of rapid return to orgasm immediately following an orgasmic experience, if re-stimulated before tensions have dropped below plateau phase response levels". [ 41 ]  Though generally reported that women do not experience a  refractory period  and thus can experience an additional orgasm, or multiple orgasms, soon after the first one, [ 2 ] [ 42 ]  some sources state that both men and women experience a refractory period because women may also experience a period after orgasm in which further sexual stimulation does not produce excitement. [ 43 ] [ 44 ]  After the initial orgasm, subsequent orgasms for women may be stronger or more pleasurable as the stimulation accumulates. [ 40 ]


Discussions of female orgasm are complicated by orgasms in women typically being divided into two categories: clitoral orgasm and vaginal (or G-spot) orgasm. [ 15 ] [ 35 ]  In 1973,  Irving Singer  theorized that there are three types of female orgasms; he categorized these as  vulval , uterine, and blended, but because he was a philosopher, "these categories were generated from descriptions of orgasm in literature rather than laboratory studies." [ 2 ]  In 1982, Ladas,  Whipple  and Perry also proposed three categories: the tenting type (derived from clitoral stimulation), the A-frame type (derived from G-spot stimulation), and the blended type (derived from clitoral and G-spot stimulation). [ 45 ]  In 1999, Whipple and Komisaruk proposed  cervix  stimulation as being able to cause a fourth type of female orgasm. [ 45 ]


Female orgasms by means other than clitoral or vaginal/G-spot stimulation are less prevalent in scientific literature, [ 15 ]  and most scientists contend that no distinction should be made between "types" of female orgasm. [ 35 ]  This distinction began with  Sigmund Freud , who postulated the concept of "vaginal orgasm" as separate from clitoral orgasm. In 1905, Freud stated that clitoral orgasms are purely an adolescent phenomenon and that upon reaching puberty, the proper response of mature women is a change-over to vaginal orgasms, meaning orgasms without any clitoral stimulation. While Freud provided no evidence for this basic assumption, the consequences of this theory were considerable. Many women felt inadequate when they could not achieve orgasm via vaginal intercourse alone, involving little or no clitoral stimulation, as Freud's theory made penile–vaginal intercourse the central component to women's sexual satisfaction. [ 46 ] [ 47 ] [ 48 ] [ 49 ]


The first major national surveys of sexual behavior in the U.S. were the  Kinsey Reports . [ 50 ]   Alfred Kinsey  was the first researcher to harshly criticize Freud's ideas about female sexuality and orgasm when, through his interviews with thousands of women, [ 50 ]  Kinsey found that most of the women he surveyed could not have vaginal orgasms. [ 47 ]  He "criticized Freud and other theorists for projecting male constructs of sexuality onto women" and "viewed the clitoris as the main center of sexual response" and the vagina as "relatively unimportant" for sexual satisfaction, relaying that "few women inserted fingers or objects into their vaginas when they masturbated." He "concluded that satisfaction from penile penetration [is] mainly psychological or perhaps the result of referred sensation". [ 47 ]


Masters and Johnson's research into the female  sexual response cycle , as well as  Shere Hite 's, generally supported Kinsey's findings about female orgasm. [ 37 ] [ 47 ] [ 51 ] [ 52 ]  Masters and Johnson's research on the topic came at the time of the  second-wave feminist movement  and inspired feminists such as  Anne Koedt , author of  The Myth of the Vaginal Orgasm , to speak about the "false distinction" made between clitoral and vaginal orgasms and women's biology not being properly analyzed. [ 53 ]


Accounts that the vagina is capable of producing orgasms continue to be subject to debate because, in addition to the vagina's low concentration of nerve endings, reports of the G-spot's location are inconsistent—it appears to be nonexistent in some women and may be an extension of another structure, such as the  Skene's gland  or the clitoris, which is a part of the Skene's gland. [ 5 ] [ 29 ] [ 33 ] [ 54 ]  In a January 2012  The Journal of Sexual Medicine  review examining years of research into the existence of the G-spot, scholars state that "[r]eports in the public media would lead one to believe the G-spot is a well-characterized entity capable of providing extreme sexual stimulation, yet this is far from the truth". [ 33 ]


Possible explanations for the G-spot were examined by Masters and Johnson, who were the first researchers to determine that the clitoral structures surround and extend along and within the labia. In addition to observing that the majority of their female subjects could only have clitoral orgasms, they found that both clitoral and vaginal orgasms had the same stages of physical response. On this basis, they argue that clitoral stimulation is the source of both kinds of orgasms, [ 51 ] [ 52 ]  reasoning that the clitoris is stimulated during penetration by friction against its hood; their notion that this provides the clitoris with sufficient sexual stimulation has been criticized by researchers such as  Elisabeth Lloyd . [ 22 ]


Australian  urologist  Helen O'Connell's 2005 research additionally indicates a connection between orgasms experienced vaginally and the clitoris, suggesting that clitoral tissue extends into the anterior wall of the vagina and that therefore clitoral and vaginal orgasms are of the same origin. [ 5 ]  Some studies, using  medical ultrasound , have found physiological evidence of the G-spot in women who report having orgasms during vaginal intercourse, [ 31 ] [ 55 ]  but O'Connell suggests that the clitoris's interconnected relationship with the vagina is the physiological explanation for the conjectured G-spot. Having used  MRI  technology which enabled her to note a direct relationship between the legs or roots of the clitoris and the erectile tissue of the "clitoral bulbs" and corpora, and the distal  urethra  and vagina, she stated that the vaginal wall is the clitoris; that lifting the skin off the vagina on the side walls reveals the bulbs of the clitoris—triangular, crescental masses of erectile tissue. [ 5 ]  O'Connell et al., who performed dissections on the female genitals of  cadavers  and used photography to map the structure of nerves in the clitoris, were already aware that the clitoris is more than just its glans and asserted in 1998 that there is more erectile tissue associated with the clitoris than is generally described in anatomical textbooks. [ 32 ] [ 51 ]  They concluded that some females have more extensive clitoral tissues and nerves than others, especially having observed this in young cadavers as compared to elderly ones, [ 32 ] [ 51 ]  and therefore whereas the majority of females can only achieve orgasm by direct stimulation of the external parts of the clitoris, the stimulation of the more generalized tissues of the clitoris via intercourse may be sufficient for others. [ 5 ]


French researchers Odile Buisson and Pierre Foldès report similar findings to that of O'Connell's. In 2008, they published the first complete 3D sonogram via medical  ultrasound  of the stimulated clitoris, and republished it in 2009 with new research, demonstrating the ways in which erectile tissue of the clitoris engorges and surrounds the vagina, arguing that women may be able to achieve vaginal orgasm via stimulation of the G-spot because the highly innervated clitoris is pulled closely to the anterior wall of the vagina when the woman is sexually aroused and during vaginal penetration. They assert that since the front wall of the vagina is inextricably linked with the internal parts of the clitoris, stimulating the vagina without activating the clitoris may be next to impossible. [ 29 ] [ 31 ] [ 56 ] [ 57 ]  In their 2009 published study, the "coronal planes during  perineal  contraction and finger penetration demonstrated a close relationship between the root of the clitoris and the anterior vaginal wall". Buisson and Foldès suggest "the special sensitivity of the lower anterior vaginal wall could be explained by pressure and movement of clitoris's root during a vaginal penetration and subsequent perineal contraction". [ 31 ] [ 57 ]


Supporting a distinct G-spot is a study by  Rutgers University , published 2011, which was the first to map the female genitals onto the sensory portion of the brain; [ 58 ]  brain scans showed that the brain registered distinct feelings between stimulating the clitoris, the cervix and the vaginal wall – where the G-spot is reported to be – when several women stimulated themselves in a  functional magnetic resonance  (fMRI) machine. [ 58 ] [ 29 ]  "I think that the bulk of the evidence shows that the G-spot is not a particular thing," stated  Barry Komisaruk , head of the research findings. "It's not like saying, 'What is the thyroid gland?' The G-spot is more of a thing like New York City is a thing. It's a region, it's a convergence of many different structures." [ 33 ]  Commenting on Komisaruk's research and other findings,  Emmanuele A. Jannini , a professor of endocrinology at the University of Aquila in Italy, acknowledges a series of essays published in March 2012 in  The Journal of Sexual Medicine , which document evidence that vaginal and clitoral orgasms are separate phenomena that activate different areas of the brain and possibly suggest key psychological differences between women. [ 29 ]


Regular difficulty reaching orgasm after ample sexual stimulation, known as  anorgasmia , is significantly more common in women than in men ( see below ). [ 23 ]  In addition to sexual dysfunction being a cause for women's inability to reach orgasm, or the amount of time for sexual arousal needed to reach orgasm being variable and longer in women than in men, other factors include a lack of communication between sexual partners about what is needed for the woman to reach orgasm, feelings of sexual inadequacy in either partner, a focus on only penetration (vaginal or otherwise), and men generalizing women's trigger for orgasm based on their own sexual experiences with other women. [ 4 ] [ 10 ] [ 20 ]


Scholars state "many couples are locked into the idea that orgasms should be achieved only through intercourse [vaginal sex]" and that "[e]ven the word  foreplay  suggests that any other form of sexual stimulation is merely preparation for the 'main event.'...Because women reach orgasm through intercourse less consistently than men, they are more likely than men to have  faked an orgasm ". [ 4 ]  Sex counselor  Ian Kerner  states, "It's a myth that using the penis is the main way to pleasure a woman." He cites research concluding that women reach orgasm about 25 percent of the time with intercourse, compared with 81 percent of the time during oral sex ( cunnilingus ). [ 59 ]


In the first large-scale empirical study worldwide to link specific practices with orgasm, reported in the  Journal of Sex Research  in 2006, demographic and sexual history variables were comparatively weakly associated with orgasm. Data was analyzed from the Australian Study of Health and Relationships, a national telephone survey of sexual behavior and attitudes and sexual health knowledge carried out in 2001–02, with a representative sample of 19,307 Australians aged 16 to 59. Practices included "vaginal intercourse alone (12%), vaginal + manual stimulation of the man's and/or woman's genitals (49%), and vaginal intercourse + manual + oral (32%)" and the "[e]ncounters may also have included other practices. Men had an orgasm in 95 percent of encounters and women in 69 percent. Generally, the more practices engaged in, the higher a woman's chance of having an orgasm. Women were more likely to reach orgasm in encounters including cunnilingus". [ 60 ]  Other studies suggest that women exposed to lower levels of prenatal  androgens  are more likely to experience orgasm during vaginal intercourse than other women. [ 10 ]


Kinsey, in his 1953 book  Sexual Behavior in the Human Female , states that exercise could bring about sexual pleasure, including orgasm. [ 61 ]  A review in 1990 on the sexual response as exercise states that the field was poorly researched and that  aerobic  or  isotonic  exercise that resembles sexual activity or sexual positions can induce sexual pleasure, including orgasm. [ 61 ]  A 2007 review of the relationship between  pelvic floor  dysfunction and sexual problems in men and women finds that they are commonly linked and suggests that  physical therapy  strengthening the pelvic floor could help address the sexual problems but that it was not well studied enough to recommend. [ 62 ]  Starting in at least 2007, the term, "coregasm" was used in popular media to refer to exercise-induced orgasm [ 63 ] [ 64 ]  or in academic parlance termed  exercise-induced sexual pleasure , [ 65 ]  and an extensive discussion of the "yogasm" occurred in a 2011  Daily Beast  posting. [ 63 ] [ 66 ]  A paper published in 2012 presents results of an online survey of women who had experienced an orgasm or other sexual pleasure during exercise. [ 63 ] [ 67 ]  The paper was widely discussed in popular media when it was published. [ 68 ] [ 69 ] [ 70 ] [ 71 ]  The authors of the paper said that research on the relationship between exercise and sexual response was still lacking. [ 63 ]


In men, the most common way of achieving orgasm is by physical sexual stimulation of the  penis . [ 2 ]  This is usually accompanied by  ejaculation , but it is possible, though rare, for men to orgasm without ejaculation (known as a "dry orgasm"). [ 18 ]   Prepubescent  boys have dry orgasms. [ 72 ]  Dry orgasms can also occur as a result of  retrograde ejaculation , [ 73 ]  or  hypogonadism . [ 74 ]  Men may also ejaculate without reaching orgasm, [ 74 ] [ 75 ]  which is known as  anorgasmic ejaculation . [ 75 ]  They may also achieve orgasm by stimulation of the  prostate  ( see below ). [ 2 ] [ 76 ]


The traditional view of male orgasm is that there are two stages: emission accompanying orgasm, almost instantly followed by a refractory period. The refractory period is the recovery phase after orgasm during which it is physiologically impossible for a man to have additional orgasms. [ 77 ] [ 78 ]  In 1966, Masters and Johnson published pivotal research about the phases of sexual stimulation. [ 11 ] [ 79 ]  Their work included women and men and—unlike Kinsey in 1948 and 1953 [ 50 ] —tried to determine the physiological stages before and after orgasm.


Masters and Johnson state in the first stage, "accessory organs contract and the male can feel the ejaculation coming; two to three seconds later the ejaculation occurs, which the man cannot constrain, delay, or in any way control" and in the second stage, "the male feels pleasurable contractions during ejaculation, reporting greater pleasure tied to a greater volume of ejaculate". [ 41 ]  They report "for the man the resolution phase includes a superimposed refractory period" and "many males below the age of 30, but relatively few thereafter, have the ability to ejaculate frequently and are subject to only very short refractory periods during the resolution phase". Masters and Johnson equate male orgasm and ejaculation and maintain the necessity for a refractory period between orgasms. [ 41 ]


There has been little scientific study of multiple orgasms in men. [ 76 ]  Dunn and Trost define multiple male orgasms as "two or more orgasms with or without ejaculation and without, or with only very limited, de-tumescence (loss of erection) during one and the same sexual encounter". [ 18 ]  Although it is rare for men to achieve multiple orgasms, [ 2 ] [ 80 ]  some men have reported having multiple consecutive orgasms, particularly without ejaculation. [ 18 ]  There may not be an obvious refractory period, and the final orgasm may cause a refractory period. [ 76 ]  Multiple orgasms are more commonly reported in very young men than in older men. [ 18 ]  In younger men, the refractory period may only last a few minutes but last more than an hour in older men. [ 73 ]


An increased infusion of  oxytocin  during ejaculation is believed to be chiefly responsible for the refractory period, and the amount by which oxytocin is increased may affect the length of each refractory period. [ 81 ]  A scientific study to successfully document natural, fully ejaculatory, multiple orgasms in an adult man was conducted at Rutgers University in 1995. During the study, six fully ejaculatory orgasms were experienced in 36 minutes, with no apparent refractory period. [ 2 ]


In both sexes, pleasure can be derived from the nerve endings around the anus and the anus itself, such as during  anal sex . Men can achieve orgasms through  prostate  stimulation alone. [ 2 ] [ 16 ]  The prostate is the male homologue (variation) to the Skene's glands (which are believed to be connected to the female G-spot), [ 84 ]  and can be sexually stimulated through anal sex, perineum massage or a vibrator. [ 85 ]  Much of the available information about prostate-induced orgasms comes from anecdotal reports by individuals, and the exact mechanisms by which such orgasms are produced are unclear; some sources suggest this occurs via stimulation of nerves in the  prostatic plexus  surrounding the organ, others suggest it is via nerves within the prostate itself, and others say changes in the brain ( neuroplasticity ) are required to derive pleasure from prostate stimulation. Regardless, prostate-induced orgasms are often reported to be intensely pleasurable. [ 86 ]  Prostate stimulation can produce a deeper orgasm, described by some men as more widespread and intense, longer-lasting, and allowing for greater feelings of ecstasy than orgasm elicited by penile stimulation only. [ 2 ] [ 86 ] [ 16 ]  The practice of  pegging  (consisting of a woman penetrating a man's anus with a  strap-on dildo ) stimulates the prostate. It is typical for a man to not reach orgasm as a receptive partner solely from anal sex. [ 87 ] [ 88 ]


For women, penile-anal penetration may also indirectly stimulate the clitoris by the shared sensory nerves, especially the  pudendal nerve , which gives off the  inferior anal nerves  and divides into the  perineal nerve  and the  dorsal nerve of the clitoris . [ 16 ]  The G-spot area, which is considered to be interconnected with the clitoris, [ 5 ] [ 16 ] [ 33 ]  may also be indirectly stimulated during anal sex. [ 89 ] [ 90 ]  Although the anus has many nerve endings, their purpose is not specifically for inducing orgasm, and so a woman achieving orgasm solely by anal stimulation is rare. [ 91 ] [ 92 ]  Direct stimulation of the clitoris, a G-spot area, or both, while engaging in anal sex can help some women enjoy the activity and reach orgasm during it. [ 25 ] [ 90 ]


The aforementioned orgasms are sometimes referred to as  anal orgasms , [ 92 ] [ 93 ]  but sexologists and sex educators generally believe that orgasms derived from anal penetration are the result of the relationship between the nerves of the anus, rectum, clitoris or G-spot area in women, and the anus's proximity to the prostate and relationship between the anal and rectal nerves in men, rather than orgasms originating from the anus itself. [ 16 ] [ 90 ] [ 92 ]


For women, stimulation of the  breast  area during sexual intercourse or foreplay, or solely having the breasts  fondled , can create mild to intense orgasms, sometimes referred to as a  breast orgasm  or  nipple orgasm . [ 58 ]  Few women report experiencing orgasm from nipple stimulation. [ 17 ] [ 94 ]  Before Komisaruk et al.'s fMRI research on nipple stimulation in 2011, reports of women achieving orgasm from nipple stimulation relied solely on  anecdotal evidence . [ 95 ]  Komisaruk's study was the first to map the female genitals onto the sensory portion of the brain; it indicates that sensation from the nipples travels to the same part of the brain as sensations from the vagina, clitoris and cervix, and that these reported orgasms are genital orgasms caused by nipple stimulation and may be directly linked to the genital sensory cortex ("the genital area of the brain"). [ 95 ] [ 96 ] [ 58 ]


An orgasm is believed to occur in part because of oxytocin, which is produced in the body during sexual excitement and arousal, and labor. It has also been shown that oxytocin is produced when a man or woman's nipples are stimulated and become erect. [ 58 ] [ 97 ]  Komisaruk also relays that preliminary data suggests that nipple nerves may directly link up with the relevant parts of the brain without uterine mediation, acknowledging the men in his study who showed the same pattern of nipple stimulation activating genital brain regions. [ 58 ]


Masters and Johnson were some of the first researchers to study the sexual response cycle in the early 1960s, based on the observation of 382 women and 312 men. They describe a cycle that begins with excitement as blood rushes into the genitals, then reaches a plateau during which they are fully aroused, which leads to orgasm, and finally resolution, in which the blood leaves the genitals. [ 11 ]


In the 1970s, Kaplan added the category of desire to the cycle, which she argues precedes sexual excitation. She states that emotions of anxiety, defensiveness, and the failure of communication can interfere with desire and orgasm. [ 98 ]  In the late 1980s and after, Rosemary Basson proposed a more cyclical alternative to what had largely been viewed as a linear progression. [ 99 ]  In her model, desire feeds arousal and orgasm and is in turn fueled by the rest of the orgasmic cycle. Rather than orgasm being the peak of the sexual experience, she suggests that it is just one point in the circle and that people could feel sexually satisfied at any stage, reducing the focus on climax as an end goal of all sexual activity. [ 100 ]


A woman's orgasm may, in some cases, last a little longer than a man's. [ 40 ] [ 42 ] [ 101 ]  Women's orgasms have been estimated to last on average approximately 20 seconds and to consist of a series of muscular contractions in the pelvic area that includes the vagina, the uterus, and the anus. [ 102 ]  For some women, on some occasions, these contractions begin soon after the woman reports that the orgasm has started and continue at intervals of about one second with initially increasing and then reducing intensity. In some instances, the series of regular contractions is followed by a few additional contractions or shudders at irregular intervals. [ 102 ]  In other cases, the woman reports having an orgasm, but no pelvic contractions are measured at all. [ 103 ]


Women's orgasms are preceded by the erection of the clitoris and moistening of the opening of the vagina. Some women exhibit a  sex flush , a reddening of the skin over much of the body due to increased blood flow to the skin. As a woman nears orgasm, the clitoral glans retracts under the clitoral hood, and the  labia minora  (inner lips) become darker. As orgasm becomes imminent, the outer third of the vagina tightens and narrows, while overall the vagina lengthens and dilates and also becomes congested from engorged soft tissue. [ 104 ]


Elsewhere in the body,  myofibroblasts  of the nipple- areolar  complex contract, causing erection of the nipples and contraction of the areolar diameter, reaching their maximum at the start of orgasm. [ 105 ]  A woman experiences full orgasm when her uterus, vagina, anus, and pelvic muscles undergo a series of rhythmic contractions. Most women find these contractions very pleasurable.


Researchers from the  University Medical Center of Groningen  in the  Netherlands  correlated the sensation of orgasm with muscular contractions occurring at a frequency of 8–13 Hz centered in the pelvis and measured in the anus. They argue that the presence of this particular frequency of contractions can distinguish between voluntary contraction of these muscles and spontaneous involuntary contractions, and appears to more accurately correlate with orgasm as opposed to other metrics like heart rate that only measure excitation. They assert that they have identified "[t]he first objective and quantitative measure that has a strong correspondence with the subjective experience that orgasm ultimately is" and state that the measure of contractions that occur at a frequency of 8–13 Hz is specific to orgasm. They found that using this metric they could distinguish between rest, voluntary muscular contractions, and even unsuccessful orgasm attempts. [ 106 ]


Since ancient times in Western Europe, women could be  medically diagnosed  with a disorder called  female hysteria , the symptoms of which included faintness, nervousness, insomnia, fluid retention, heaviness in abdomen, muscle spasm, shortness of breath, irritability, loss of appetite for food or sex, and "a tendency to cause trouble". [ 107 ]  Women considered to have the condition would sometimes undergo "pelvic massage:" stimulation of the genitals by the doctor until the woman experienced "hysterical paroxysm" (i.e., orgasm). Paroxysm was regarded as a medical treatment and not a sexual release. [ 107 ]  The disorder has ceased to be recognized as a medical condition since the 1920s.


As a man nears orgasm during stimulation of the penis, he feels an intense and highly pleasurable pulsating sensation of  neuromuscular   euphoria . These pulsating sensations originate from the contractions of pelvic floor muscles that begin in the anal sphincter and travel to the tip of the penis, commonly described as a "throbbing" or "tingling" sensation. They eventually increase in speed and intensity as the orgasm approaches, until a final "plateau" (the orgasmic) pleasure is sustained for several seconds. [ 41 ]


During orgasm a male experiences rapid, rhythmic contractions of the  anal sphincter , the prostate, and the  bulbospongiosus muscles  of the penis. The  sperm  are transmitted up the  vasa deferentia  from the  testicles , into the prostate gland as well as through the  seminal vesicles  to produce what is known as  semen . [ 41 ]  The prostate produces a secretion that forms one of the components of ejaculate. Except for in cases of a dry orgasm, contraction of the sphincter and prostate force stored semen to be expelled through  the penis's urethral opening . The process takes from three to ten seconds and produces a pleasurable feeling. [ 15 ] [ 41 ]  Ejaculation may continue for a few seconds after the euphoric sensation gradually tapers off. It is believed that the feeling of "orgasm" varies from one man to another. [ 15 ]   After ejaculation, a refractory period usually occurs, during which a man cannot achieve another orgasm. This can last anywhere from less than a minute to several hours or days, depending on age and other individual factors. [ 42 ] [ 43 ] [ 44 ]


There have been very few studies correlating orgasm and brain activity in real time. One study examined 12 healthy women using a  positron emission tomography  (PET) scanner while they were being stimulated by their partners. Brain changes were observed and compared between states of rest, sexual stimulation, faked orgasm, and actual orgasm. Differences were reported in the brains of men and women during stimulation. Changes in brain activity were observed in both sexes, as regions associated with behavioral control, fear, and anxiety shut down. Regarding these,  Gert Holstege  said in an interview with  The Times , "What this means is that deactivation, letting go of all fear and anxiety, might be the most important thing, even necessary, to have an orgasm." [ 108 ]


While stroking the clitoris, the parts of the female brain responsible for processing fear, anxiety, and behavioral control start to diminish in activity. This reaches a peak at orgasm when the female brain's emotion centers are effectively closed down to produce an almost trance-like state. Holstege is quoted as saying, at the 2005 meeting of the European Society for Human Reproduction and Development: "At the moment of orgasm, women do not have any emotional feelings." [ 109 ]  A subsequent report by Rudie Kortekaas, et al. states, "Gender commonalities were most evident during orgasm... From these results, we conclude that during the sexual act, differential brain responses across genders are principally related to the stimulatory (plateau) phase and not to the orgasmic phase itself." [ 7 ]  Research has shown that as in women, the emotional centers of a man's brain also become deactivated during orgasm but to a lesser extent than in women. Brain scans of both sexes have shown that the  pleasure centers  of a man's brain show more intense activity than in women during orgasm. [ 110 ]  Male and female brains demonstrate similar changes during orgasm, with brain activity scans showing a temporary decrease in the  metabolic  activity of large parts of the  cerebral cortex  with normal or increased metabolic activity in the limbic areas of the brain. [ 7 ]


EEG  tracings from volunteers during orgasm were first obtained by Mosovich and Tallaferro in 1954, [ 111 ]  who recorded EEG changes resembling  petit mal  or the clonic phase of a  grand mal  seizure. Further studies in this direction were carried out by Sem-Jacobsen (1968), Heath (1972), Cohen et al. (1976), [ 112 ]  and others. [ 113 ] [ 114 ]  Sarrel et al. reported a similar observation in 1977. These reports continue to be cited. [ 115 ]  Unlike them, Craber et al. (1985) failed to find any distinctive EEG changes in four men during masturbation and ejaculation; the authors concluded that the case for the existence of EEG changes specifically related to sexual arousal and orgasm remained unproven. [ 116 ]  So disagreement arises as to whether the experiment conducted by Mosovich and Tallaferro casts a new light on the nature of orgasm. In some recent studies, authors tend to adopt the opposite point of view that there are no remarkable EEG changes during ejaculation in humans. [ 117 ]


Orgasm, and sexual activity as a whole, are physical activities that can require exertion of many major bodily systems. A 1997 study in the  BMJ  based upon 918 men aged 45–59 found that after a ten-year follow-up, men who had fewer orgasms were twice as likely to die of any cause as those having two or more orgasms per week. [ 118 ]  A follow-up in 2001 which focused more specifically on  cardiovascular  health found that having sex three or more times per week was associated with a 50 percent reduction in the risk of heart attack or stroke. There is some research suggesting that greater resting heart rate variability is associated with orgasms through penile-vaginal intercourse without additional simultaneous clitoral stimulation. [ 29 ]


A small percentage of men have a disease called  postorgasmic illness syndrome  (POIS), which causes severe muscle pain throughout the body and other symptoms immediately following ejaculation. The symptoms last for up to a week. [ 119 ] [ 120 ] [ 121 ]  Some doctors speculate that the frequency of POIS "in the population may be greater than has been reported in the academic literature", [ 122 ]  and that many people with POIS are undiagnosed. [ 123 ]


The inability to have an orgasm, or regular difficulty reaching orgasm after ample sexual stimulation, is called anorgasmia or inorgasmia. [ 124 ]  If a male experiences erection and ejaculation but no orgasm, he is said to have  sexual anhedonia  (a condition in which an individual cannot feel pleasure from an orgasm) or ejaculatory  anhedonia . Anorgasmia is significantly more common in women than in men, [ 125 ] [ 126 ]  which has been attributed to the lack of  sex education  about women's bodies, especially in  sex-negative  cultures, such as clitoral stimulation usually being key for women to orgasm. [ 126 ]


Approximately 25 percent of women report difficulties with orgasm, [ 127 ]  10% of women have never had an orgasm, [ 128 ]  and 40 percent or 40–50 percent have either complained about sexual dissatisfaction or experienced difficulty becoming sexually aroused at some point in their lives. [ 129 ]  A 1994 study by Laumann et al. found that 75 percent of men and 29 percent of women always had orgasms with their spouse, while 40 percent of men and 80 percent of women thought their spouse always orgasmed during sex. [ 130 ]  These rates were different in non-marital straight relationships (cohabitational, long-term and short-term heterosexual relationships), with rates increasing to 81 percent for men and 43 percent for women orgasming during sex with their short-term partners, and 69 percent for men and 83 percent for women thinking their short-term partners always orgasmed. [ 130 ]  Women are much more likely to be nearly always or always orgasmic when alone than with a partner. [ 8 ]  In a 1996 study by Davis et   al., 62 percent of women in a partnered relationship said they were satisfied with the frequency/consistency of their orgasms. [ 8 ]  Additionally, some women express that their most satisfying sexual experiences entail being connected to someone, rather than solely basing satisfaction on orgasm. [ 131 ] [ 132 ]


Kinsey's 1953  Sexual Behavior in the Human Female  shows that over the previous five years of sexual activity, 78 percent of women had orgasms in 60–100 percent of  sexual encounters with other women , compared with 55 percent for heterosexual sex. [ 133 ]  Kinsey attributed this difference to female partners knowing more about women's sexuality and how to optimize women's sexual satisfaction than male partners do. [ 4 ]  Like Kinsey, scholars such as Peplau, Fingerhut, and Beals (2004) and Diamond (2006) found that lesbians have orgasms more often and more easily in sexual interactions than heterosexual women do, [ 4 ]  and that female partners are more likely to emphasize the emotional aspects of lovemaking. [ 4 ]  In contrast, research by Diane Holmberg and Karen L. Blair (2009), published in the  Journal of Sex Research , found that women in same-sex relationships enjoyed identical sexual desire, sexual communication, sexual satisfaction, and satisfaction with orgasm as their heterosexual counterparts. [ 134 ]


If orgasm is desired, anorgasmia may be attributed to an inability to relax. It may be associated with performance pressure and an unwillingness to pursue pleasure, as separate from the other person's satisfaction; often, women worry so much about the pleasure of their partner that they become anxious, which manifests as impatience with the delay of orgasm for them. This delay can lead to frustration of not reaching orgasmic sexual satisfaction. [ 127 ]  Psychoanalyst  Wilhelm Reich , in his 1927 book  Die Funktion des Orgasmus  (published in English in 1980 as  Genitality in the Theory and Therapy of Neurosis ) was the first to make orgasm central to the concept of mental health, and he defined  neurosis  in terms of blocks to having  orgastic potency . Although orgasm dysfunction can have psychological components, physiological factors often play a role. For instance, delayed orgasm or the inability to achieve orgasm is a common side effect of many medications.


Specifically, with simultaneous orgasm and similar practices, many sexologists claim that the problem of  premature ejaculation [ 135 ]  is closely related to the idea encouraged by a scientific approach in the early 20th century when mutual orgasm was overly emphasized as an objective and a sign of true sexual satisfaction in intimate relationships. Menopause  may involve loss of hormones supporting sexuality and genital functionality. Vaginal and clitoral atrophy and dryness affect up to 50–60 percent of postmenopausal women. [ 136 ]  Testosterone levels in men fall as they age. Sexual dysfunction overall becomes more likely with poor physical and emotional health. "Negative experiences in sexual relationships and overall well-being" are associated with sexual dysfunction. [ 137 ] [ 138 ]


The function or functions of the human female orgasm have been debated among researchers. [ 139 ]  Researchers have several hypotheses about the role if any, of the female orgasm in the reproductive and therefore evolutionary process. [ 9 ] [ 10 ] [ 22 ] [ 49 ]  The literature started with the argument that female orgasm is a byproduct of shared early male  ontogeny , where male orgasm is an  adaptation . [ 140 ]  Research has shifted to investigate and also support the sire-choice hypothesis, which proposes that female orgasm has been shaped by  natural selection  to function in the selection of high-quality sires (male parents) for offspring. Therefore, orgasm increases the chances of conceiving with males of high genetic quality. [ 141 ] [ 142 ]  Research by  Randy Thornhill  et al. (1995) suggests that female orgasm is more frequent during intercourse with a male partner with low  fluctuating asymmetry . [ 143 ]


Wallen K and Lloyd EA state, "In men, orgasms are under strong selective pressure as orgasms are coupled with ejaculation and thus contribute to male reproductive success. By contrast, women's orgasms in intercourse are highly variable and are under little selective pressure as they are not a reproductive necessity." [ 10 ]


Desmond Morris  suggests in his 1967 popular science book  The Naked Ape  that the female orgasm evolved to encourage physical intimacy with a male partner and help reinforce the  pair bond . Morris suggested that the relative difficulty in achieving female orgasm, in comparison to the male's, might be favorable in  Darwinian  evolution by leading the female to select  mates  who bear qualities like patience, care, imagination, and intelligence, as opposed to qualities like size and aggression, which pertain to mate selection in other primates. Such advantageous qualities thereby become accentuated within the species, driven by the differences between male and female orgasms. If males were motivated by and taken to the point of, orgasm in the same way as females, those advantageous qualities would not be needed, since self-interest would be enough.


There are theories that the female orgasm might increase fertility. [ 9 ] [ 22 ] [ 49 ]  For example, it has been suggested that the 30 percent reduction in the size of the vagina could help clench the penis (much like, or perhaps caused by, the  pubococcygeus muscles ), which would make it more stimulating for the male (thus ensuring faster or more voluminous ejaculation). The British biologists Baker and Bellis have suggested that the female orgasm may have a  peristalsis  or "upsuck" action (similar to the  esophagus ' ability to swallow when upside down), resulting in the retaining of favorable sperm and making conception more likely. [ 144 ]  They posited a role of female orgasm in  sperm competition .


The observation that women tend to reach orgasm more easily when they are ovulating also has led to the suggestion that it is tied to increasing fertility. [ 145 ]  Evolutionary biologist Robin Baker argues in  Sperm Wars  that occurrence and timing of orgasms are all a part of the female body's unconscious strategy to collect and retain sperm from more evolutionary fit men. [ 146 ]  This theory suggests that an orgasm during intercourse functions as a bypass button to a woman's natural cervical filter against sperm and pathogens, and that an orgasm before functions to strengthen the filter.


Desmond Morris proposed that orgasm might facilitate conception by exhausting the female and keeping her horizontal, thus preventing the sperm from leaking out. This possibility sometimes called the "Poleaxe Hypothesis" or the "Knockout Hypothesis",  is now considered unlikely. A 1994  Learning Channel  documentary on sex had fiber optic cameras inside the vagina of a woman while she had sexual intercourse. During her orgasm, her pelvic muscles contracted and her  cervix  repeatedly dipped into a pool of semen in the  vaginal fornix , which might ensure that sperm would proceed by the  external orifice of the uterus , making conception more likely. [ 147 ]


Evolutionary psychologists Christopher Ryan and Cacilda Jethá, in their discussion of the female orgasm, address how long it takes for females to achieve orgasm compared to males, and females' ability to have multiple orgasms, hypothesizing how especially well suited to multiple partners and  insemination  this is. They quote  primate sexuality  specialist Alan Dixson in saying that the monogamy-maintenance explanation for female orgasm "seems far-fetched" because "females of other primate species, and particularly those with multimale-multifemale [promiscuous] mating systems such as macaques and chimpanzees, exhibit orgasmic responses in the absence of such bonding or the formation of stable family units." On the other hand, Dixson states that "Gibbons, which are primarily monogamous, do not exhibit obvious signs of female orgasm." [ 148 ]


The  female promiscuity  explanation of female sexuality was echoed at least 12 years earlier by other evolutionary biologists, and there is increasing scientific awareness of the female  proceptive phase . [ 149 ]  Though Dixson classifies humans as mildly polygynous in his survey of primate sexuality, he appears to have doubts, when he writes, "One might argue that ... the female's orgasm is rewarding, increases her willingness to copulate with a variety of males rather than one partner, and thus promotes sperm competition." Ryan and Jethá use this as evidence for their theory that  partible paternity  and promiscuity was common for early modern humans. [ 148 ]


The clitoris is  homologous  to the penis; that is, they both develop from the same embryonic structure. [ 27 ] [ 28 ]  While researchers such as  Geoffrey Miller ,  Helen Fisher ,  Meredith Small  and  Sarah Blaffer Hrdy  "have viewed the clitoral orgasm as a legitimate adaptation in its own right, with major implications for female sexual behavior and sexual evolution," [ 9 ]  others, such as  Donald Symons  and  Stephen Jay Gould , have asserted that the clitoris is  vestigial  or nonadaptive and that the female orgasm serves no particular evolutionary function. [ 9 ] [ 49 ]  Gould acknowledged that "most female orgasms emanate from a clitoral, rather than vaginal (or some other), site" and stated that his nonadaptive belief "has been widely misunderstood as a denial of either the adaptive value of female orgasm in general or even as a claim that female orgasms lack significance in some broader sense". He explained that although he accepts that "clitoral orgasm plays a pleasurable and central role in female sexuality and its joys," "[a]ll these favorable attributes, however, emerge just as clearly and just as easily, whether the clitoral site of orgasm arose as a  spandrel  or an adaptation". He said that the "male biologists who fretted over [the adaptionist questions] simply assumed that a deeply vaginal site, nearer the region of fertilization, would offer greater selective benefit" due to their Darwinian,  summum bonum  beliefs about enhanced reproductive success. [ 49 ]


Proponents of the nonadaptive hypothesis, such as Elisabeth Lloyd, refer to the relative difficulty of achieving female orgasm through vaginal sex, the limited evidence for increased fertility after orgasm, and the lack of statistical correlation between the capacity of a woman to orgasm and the likelihood that she will engage in intercourse. [ 22 ] [ 150 ]  "Lloyd is by no means against evolutionary psychology. Quite the opposite; in her methods and in her writing, she advocates and demonstrates a commitment to the careful application of evolutionary theory to the study of human behavior," stated  Meredith L. Chivers . She added that Lloyd "meticulously considers the theoretical and empirical bases for each account and ultimately concludes that there is little evidence to support an adaptionist account of female orgasm" and that Lloyd instead "views female orgasm as an ontogenetic leftover; women have orgasms because the urogenital neurophysiology for orgasm is so strongly selected for in males that this developmental blueprint gets expressed in females without affecting fitness, just as males have nipples that serve no fitness-related function". [ 150 ]


A 2005  twin study  found that one in three women reported never or seldom achieving orgasm during sexual intercourse, and only one in ten always orgasmed. This variation in the ability to orgasm, generally thought to be psychosocial, was found to be 34 percent to 45 percent genetic. The study, examining 4000 women, was published in  Biology Letters , a  Royal Society  journal. [ 151 ] [ 152 ]  Elisabeth Lloyd has cited this as evidence for the notion that female orgasm is not adaptive. [ 22 ] [ 153 ]


Miller, Hrdy, Helen O'Connell, and  Natalie Angier  have criticized the "female orgasm is vestigial" hypothesis as understating and devaluing the psychosocial value of the female orgasm. [ 9 ]  Hrdy stated that the hypothesis smacks of  sexism . [ 154 ]  O'Connell said, "It boils down to rivalry between the sexes: the idea that one sex is sexual and the other reproductive. The truth is that both are sexual and both are reproductive." [ 5 ]  O'Connell used  MRI  technology to define the true size and shape of the clitoris, suggesting that it extends into the anterior wall of the vagina ( see above ).


O'Connell describes typical textbook descriptions of the clitoris as lacking detail and including inaccuracies, saying that the work of  Georg Ludwig Kobelt  in the early 19th century provides a most comprehensive and accurate description of clitoral anatomy. She argues that the bulbs appear to be part of the clitoris and that the distal urethra and vagina are intimately related structures, although they are not erectile in character, forming a tissue cluster with the clitoris that appears to be the center of female sexual function and orgasm. [ 5 ]  By contrast, Nancy Tuana, at the 2002 conference for  Canadian Society of Women in Philosophy , argues that the clitoris is unnecessary in reproduction, but that this is why it has been "historically ignored", mainly because of "a fear of pleasure. It is pleasure separated from reproduction. That's the fear". She reasoned that this fear is the cause of the ignorance that veils female sexuality. [ 155 ]


Brody Costa et al. suggest that women's vaginal orgasm consistency is associated with being told in childhood or adolescence that the vagina is the important zone for inducing female orgasms. Other proposed factors include how well women focus mentally on vaginal sensations during penile-vaginal intercourse, the greater duration of intercourse, and their preference for above-average penis length. [ 156 ]  Costa theorizes that vaginal orgasm is more prevalent among women with a prominent  tubercle of the upper lip . [ 157 ]  His research indicates that "[a] prominent and sharply raised lip tubercle has been associated with greater odds ( odds ratio  = 12.3) of ever having a vaginal orgasm, and also with greater past month vaginal orgasm consistency (an effect driven by the women who never had a vaginal orgasm), than less prominent lip tubercle categories." Lip tubercle was not associated with social desirability responding, or with orgasm triggered by masturbation during penile-vaginal sex, solitary or partner clitoral or vaginal masturbation, vibrator, or cunnilingus. [ 157 ]


An empirical study carried out in 2008 provides evidence for Freud's implied link between the inability to have a vaginal orgasm and psychosexual  immaturity . In the study, women reported their past month's frequency of different sexual behaviors and corresponding orgasm rates and completed the Defense Style Questionnaire (DSQ-40), which is associated with various  psychopathologies . The study concluded that a "vaginal orgasm was associated with less somatization, dissociation, displacement, autistic fantasy, devaluation, and isolation of affect." Moreover, "vaginally anorgasmic women had immature defenses scores comparable to those of established (depression, social anxiety disorder, panic disorder, and obsessive–compulsive disorder) outpatient psychiatric groups." In the study, a vaginal orgasm (as opposed to a clitoral orgasm) was defined as being triggered solely by penile–vaginal intercourse. [ 158 ]  According to  Wilhelm Reich , the lack of women's capacity to have a vaginal orgasm is due to a lack of  orgastic potency , which he believed to be the result of culture's suppression of genital sexuality. [ 159 ]


Medical research shows that the genital reflex is also regulated by the spinal cord and not necessarily under conscious control. [ 160 ] [ 161 ] [ 162 ]  An involuntary orgasm may occur as the result of  sexual assault  or  rape , which may result in feelings of  shame  caused by internalization of  victim-blaming  attitudes. [ 163 ] [ 164 ]  The incidence of those who experience unsolicited sexual contact and experience orgasm is very low, though possibly under-reported due to shame or embarrassment of the victim. Such orgasms may happen to either sex. [ 164 ]


An unwanted orgasm may arise from a  persistent genital arousal disorder . In consensual  BDSM  play,  forced orgasm  may be practiced to exercise orgasm control.


Tantric sex , which is not the same as  Buddhist tantra (Vajrayana) , is the ancient Indian spiritual tradition of sexual practices. It attributes a different value to orgasm than traditional cultural approaches to sexuality. Some practitioners of  tantric  sex aim to eliminate orgasm from sexual intercourse by remaining for a long time in the pre-orgasmic and non-emission state. Advocates of this, such as  Rajneesh , claim that it eventually causes orgasmic feelings to spread out to all of one's conscious experience. [ 165 ] [ 166 ]


Advocates of tantric and neo-tantric sex who claim that Western culture focuses too much on the goal of climactic orgasm, which reduces the ability to have intense pleasure during other moments of the sexual experience, suggest that eliminating this enables a richer, fuller, and more intense connection. [ 167 ]


Orgasm has been widely described in literature over the centuries. In antiquity,  Latin literature  addressed the subject as much as  Greek literature : Book III of  Ovid 's  Metamorphoses  retells a discussion between  Jove  and  Juno , in which the former states: "The sense of pleasure in the male is far / More dull and dead than what you females share." [ 168 ]  Juno rejects this thought; they agree to ask the opinion of  Tiresias  ("who had known  Venus /Love in both ways," having lived seven years as a female). [ 169 ]  Tiresias offends Juno by agreeing with Jove, and she strikes him blind on the spot (Jove lessens the blow by giving Tiresias the gift of foresight, and long life). [ 170 ]  Earlier, in the  Ars Amatoria , Ovid states that he abhors sexual intercourse that fails to complete both partners. [ 171 ]


The theme of orgasm survived during  Romanticism  and is incorporated in many  homoerotic  works. In  FRAGMENT: Supposed to be an Epithalamium of Francis Ravaillac and Charlotte Cordé ,  Percy Bysshe Shelley , "a translator of extraordinary range and versatility", [ 172 ]  wrote the phrase "No life can equal such a death." That phrase has been seen as a metaphor for orgasm, [ 173 ]  and it was preceded by the rhythmic urgency of the previous lines "Suck on, suck on, I glow, I glow!", which has been seen as alluding to  fellatio . [ 173 ]  For Shelley, orgasm was "the almost involuntary consequences of a state of abandonment in the society of a person of surpassing attractions". [ 174 ]   Edward Ellerker Williams , the last love of Shelley's life, was remembered by the poet in "The Boat on the Serchio", which has been considered as possibly "the grandest portrayal of orgasm in literature": [ 173 ]  Shelley, in this poem, associates orgasm with death when he writes "the death which lovers love". [ 173 ]  In  French literature , the term  la petite mort  (the little death) is a famous  euphemism  for orgasm; [ 175 ]  it is the representation of the man who forgets himself and the world during orgasm.  Jorge Luis Borges , in the same vision, wrote in one of the several  footnotes  of " Tlön, Uqbar, Orbis Tertius " that one of the churches of  Tlön  claims  Platonically  that "All men, in the vertiginous moment of coitus, are the same man. All men who repeat a line from  Shakespeare   are  William Shakespeare." [ 176 ]  Shakespeare himself was knowledgeable of this idea: lines "I will live in thy heart, die in thy lap, and be buried in thy eyes" and "I will die bravely, like a smug bridegroom", said respectively by  Benedick  in  Much Ado About Nothing  and by King Lear in  the play of that ilk , [ 177 ]  is interpreted as "to die in a woman's lap" = "to experience a sexual orgasm". [ 178 ]


Freud with his psychoanalytic projects, in  The Ego and the Id  (1923), speculates that sexual satisfaction by orgasm make  Eros  ("life instinct") exhausted and leaves the field open to  Thanatos  ("death instinct"), in other words, with orgasm Eros fulfills its mission and gives way to Thanatos. [ 179 ]  Other modern authors have chosen to represent the orgasm without metaphors. In the novel  Lady Chatterley's Lover  (1928), by  D. H. Lawrence , we can find an explicit narrative of a sexual act between a couple: "As he began to move, in the sudden helpless orgasm there awoke in her strange thrills rippling inside her..." [ 180 ]


The mechanics of male orgasm are similar in most male mammals. [ 181 ]  Females of all mammal and some non-mammal species, such as alligators, [ 182 ]  have clitorises. [ 183 ] [ 184 ]  There has been ongoing research about the  sexuality of dolphins , one of many species which engage in sexual intercourse for  reasons other than reproduction . [ 185 ]  The duration of orgasm varies considerably among different mammal species. [ 186 ]


Orgasmic epilepsy  is a rare form of  epilepsy  that involves  auras  in which  spontaneous orgasms  occur. [ 1 ] [ 4 ] [ 2 ] [ 3 ]  Due to their rarity and sensitive nature, they have mostly been reported as  single cases  and  case series . [ 2 ] [ 3 ] [ 4 ]  A broader category is epilepsy with  sexual  auras generally. [ 1 ]  There are similarities and overlap of orgasmic epilepsy with  ecstatic epilepsy  and certain other forms of epilepsy. [ 1 ] [ 4 ]  Orgasmic seizures were first reported in 1960 and a number of additional cases have been reported since then. [ 4 ]


This article about a medical condition affecting the nervous system is a  stub . You can help Wikipedia by  expanding it .


Paṇḍaka  is a  Sanskrit  and  Pali   sexuality  term which does not have precise English translation, but incorporates (or perhaps confuses) multiple concepts associated with  immaturity ,  voyeurism ,  impotence  and  infertility .  It has been studied under the auspices of  Theravada   Buddhist  thought.


In the  Vinaya   Pali Canon , 4 gender types are defined: male, female,  ubhatobyañjanaka  and pandaka.   ubhatobyañjanaka  refers to  intersex  or literally  a person with the signs of both binary sexes/genders . Paṇḍaka is a less clear cut case, all references have a central theme: some form of  deficiency in male sexual reproductive capacity or reproductive desire.  In traditional Hindu pre-scientific thought, all reproductive capacity (or burden) has been assigned to the sperm and  lingam  with no credit to the female or egg.


The Pali literature makes reference to five types of pandaka: [ 1 ] [ 2 ]


In the crackdowns on  crime  in  post-coup   Thailand , there is draft legislation to clean out crime and sociopaths from the  Sangha , and in this drive, a motion to criminalize  sexual deviant behaviours  within it, yet the very definitions of  sexual deviancy  or  paraphilia  are being challenged and revisited by scholars. [ 3 ]


Physical attractiveness  is the degree to which a person's physical features are considered  aesthetically  pleasing or  beautiful . The term often implies  sexual attractiveness  or desirability, but can also be distinct from either. There are many factors which influence one person's attraction to another, with physical aspects being one of them. Physical attraction itself includes universal perceptions common to all human  cultures  such as  facial symmetry , [ 9 ]   sociocultural  dependent attributes, and personal  preferences  unique to a particular  individual . [ 10 ]


In many cases, humans subconsciously attribute positive characteristics, such as  intelligence  and honesty, to physically attractive people, a  psychological phenomenon  called the  Halo effect . [ 11 ]  Research done in the United States and United Kingdom found that objective [ 12 ]  measures of physical attractiveness and intelligence are  positively correlated , and that the association between the two attributes is stronger among men than among women. [ 13 ]   Evolutionary psychologists  have tried to answer why individuals who are more physically attractive should also, on average, be more intelligent, and have put forward the notion that both general intelligence and physical attractiveness may be indicators of underlying  genetic fitness . [ 13 ]  A person's physical characteristics can signal cues to  fertility  and health, [ 14 ] [ 15 ] [ 16 ]  with statistical modeling studies showing that the facial shape variables that reflect aspects of physiological health, including body fat and blood pressure, also influence observers' perceptions of health. [ 17 ]  Attending to these factors increases reproductive success, furthering the representation of one's genes in the population. [ 18 ]


Heterosexual men tend to be attracted to women who have a youthful appearance and exhibit features such as a  symmetrical face , [ 19 ]  full breasts, full lips, and a low  waist–hip ratio . [ 20 ] [ 21 ]  Heterosexual women tend to be attracted to men who are taller than them and who display a high degree of facial symmetry,  masculine  facial  dimorphism ,  upper body strength , broad shoulders, a relatively narrow waist, and a V-shaped torso. [ 22 ] [ 23 ] [ 24 ] [ 25 ]


Generally, physical attractiveness can be viewed from a number of perspectives; with universal perceptions being common to all human  cultures , cultural and  social  aspects, and individual subjective preferences. The perception of attractiveness can have a significant effect on how people are judged in terms of employment or social opportunities, friendship, sexual behaviour, and marriage. [ 26 ]


Some physical features are attractive in both men and women, particularly bodily [ 27 ]  and facial symmetry, [ 28 ] [ 29 ] [ 30 ] [ 31 ]  although one contrary report suggests that "absolute flawlessness" with perfect symmetry can be "disturbing". [ 32 ]  Symmetry may be evolutionarily beneficial as a sign of health because asymmetry "signals past illness or injury". [ 33 ]  One study suggested people were able to "gauge beauty at a subliminal level" by seeing only a glimpse of a picture for one-hundredth of a second. [ 33 ]  Other important factors include youthfulness, skin clarity and smoothness of skin; and "vivid colour" in the eyes and hair. [ 28 ]  However, there are numerous differences based on gender.


A 1921 study of the reports of college students regarding those traits argued that static traits, such as beauty or ugliness of features, hold a position subordinate to groups of physical elements like expressive behaviour, affectionate disposition, grace of manner, aristocratic bearing, social accomplishments and personal habits. [ 34 ]


Grammer and colleagues have identified eight "pillars" of beauty: youthfulness, symmetry,  averageness , sex-hormone markers,  body odor , motion, skin  complexion , and hair texture. [ 35 ]  Traditionally in  Samoa , body fat was acceptable or attractive. [ 36 ]


An Italian study published in 2008 analyzed the positions of the 50  soft-tissue  landmarks of the faces of 324  white   Northern Italian   adolescent  boys and girls to compare the features of a group of 93 "beautiful" individuals selected by a commercial  casting  agency with those of a reference group with normal dentofacial dimensions and proportions. The research found that, in comparison with the reference group, the attractive adolescents tended to have the following characteristics:


Some tendencies differed by age and sex:


The study concluded that attractive adolescents had more  neotenous  and juvenile features, but older attractive boys also showed tendencies towards  sexual dimorphism . [ 37 ]


Contrary to  common misconception , one study finds that non-severe facial scarring increases male attractiveness for short-term relationships. [ 38 ]


Symmetrical faces and bodies may be signs of good inheritance to women of child-bearing age seeking to create healthy offspring. Studies suggest women are less attracted to men with asymmetrical faces, [ 39 ]  and symmetrical faces correlate with long-term mental performance [ 40 ]  and are an indication that a man has experienced "fewer genetic and environmental disturbances such as diseases, toxins, malnutrition or genetic mutations" while growing. [ 40 ]  Since achieving symmetry is a difficult task during human growth, requiring billions of cell reproductions while maintaining a parallel structure, achieving symmetry is a visible signal of genetic health.


Studies have also suggested that women at peak  fertility  were more likely to fantasize about men with greater facial symmetry, [ 41 ]  and other studies have found that male symmetry was the only factor that could significantly predict the likelihood of a woman experiencing  orgasm  during sex. Women with partners possessing greater symmetry reported significantly more copulatory female orgasms than were reported by women with partners possessing low symmetry, even with many potential confounding variables controlled. [ 42 ]  This finding has been found to hold across different cultures. It has been argued that masculine facial dimorphism (in men) and symmetry in faces are signals advertising genetic quality in potential mates. [ 43 ]  Low facial and body  fluctuating asymmetry  may indicate good health and intelligence, which are desirable features. [ 44 ]  Studies have found that women who perceive themselves as being more physically attractive are more likely to favour men with a higher degree of facial symmetry than are women who perceive themselves as being less physically attractive. [ 45 ]  It has been found that symmetrical females and males have a tendency to begin to have  sexual intercourse  at an earlier age, to have more sexual partners, and to have more  one-night stands . They are also more likely to engage in  infidelity . [ 46 ]  A study of quarterbacks in the  American National Football League  found a positive correlation between facial symmetry and salaries. [ 29 ]


Double-blind  studies found that women prefer the scent of men who are rated as facially attractive. [ 47 ]  For example, both males and females were more attracted to the natural scent of individuals who had been rated by consensus as facially attractive. [ 48 ]  Additionally, it has also been shown that women have a preference for the scent of men with more symmetrical faces, and that women's preference for the scent of more symmetrical men is strongest during the most fertile period of their  menstrual cycle . [ 49 ]  Within the set of normally cycling women, individual women's preference for the scent of men with high facial symmetry correlated with their probability of conception. [ 49 ]  Men's body odor is also affected by their diet, with women expressing preferences for male body odor associated with increased dietary fruit, vegetable and protein content, and reduced  carbohydrate  content. [ 50 ]


Studies have explored the genetic basis behind such issues as facial symmetry and body scent and how they influence physical attraction. In one study in which women wore men's T-shirts, researchers found that women were more attracted to the bodily scents in shirts of men who had a different type of gene section within the DNA called  major histocompatibility complex (MHC) . [ 51 ]  MHC is a large gene area within the DNA of  vertebrates  which encodes proteins dealing with the  immune system [ 52 ]  and which influences individual bodily odors. [ 53 ]  One hypothesis is that humans are naturally attracted by the sense of smell and taste to others with  dissimilar  MHC sections, perhaps to avoid subsequent  inbreeding  while increasing the genetic diversity of offspring. [ 52 ]  Furthermore, there are studies showing that women's natural attraction for men with dissimilar immune profiles can be distorted with use of birth control pills. [ 53 ]  Other research findings involving the genetic foundations of attraction suggest that MHC heterozygosity positively correlates with male facial attractiveness. Women judge the faces of men who are heterozygous at all three MHC loci to be more attractive than the faces of men who are homozygous at one or more of these loci. Additionally, a second experiment with genotyped women raters, found these preferences were independent of the degree of MHC  similarity  between the men and the female rater. With MHC heterozygosity independently seen as a genetic advantage, the results suggest that facial attractiveness in men may be a measure of genetic quality. [ 54 ] [ 55 ]  General genetic heterozygosity has been demonstrated to be related to attractiveness in that people with mixed genetic backgrounds (i.e.,  mixed race people ) as seen as more attractive than people with a more similar genetic parents. (i.e., single race people). [ 56 ]  However, some studies have not found that mixed race individuals are rated as more attractive, and one found that only certain mixes were rated as more attractive; this study argued that equating race with genetics was incorrect and argued for social influences as the cause. [ 57 ]


A 2010 study by American dating site  OkCupid  on 200,000 of its male and female users found that heterosexual women  –  except those during their early to mid-twenties –  are open to relationships with both somewhat older and somewhat younger men; they have a larger potential dating pool than men until age 26. At age 20, women, in a "dramatic change", begin sending private messages to significantly older men. At age 29, they become "even more open to older men". Male desirability to women peaks in the late 20s and does not fall below the average for all men until 36. [ 58 ]  Other research indicates that women, irrespective of their own age, are attracted to men who are the same age or older. [ 59 ]


For the Romans especially, "beardlessness" and "smooth young bodies" were considered beautiful to both men and women. [ 60 ]  For Greek and Roman men, the most desirable traits of boys were their "youth" and "hairlessness". Pubescent boys were considered a socially appropriate object of male desire, while post-pubescent boys were considered to be "ἔξωροι" or "past the prime". [ 60 ]  This was largely in the context of  pederasty  (adult male interest in adolescent boys). Today, men and women's attitudes towards male beauty have changed. For example, body hair on men may even be preferred ( see below ).


A 1984 study said that gay men tend to prefer gay men of the same age as ideal partners, but there was a  statistically significant  effect ( p  < 0.05) of masculinity-femininity. The study said that more  feminine men  tended to prefer relatively older men than themselves and more masculine men tended to prefer relatively younger men than themselves. [ 61 ]


Cross-cultural data shows that the reproductive success of women is tied to their youth and physical attractiveness, [ 62 ]  such as the pre-industrial  Sami  where the most reproductively successful women were 15 years younger than their man. [ 63 ]  One study covering 37 cultures showed that, on average, a woman was 2.5 years younger than her male partner, with the age difference in Nigeria and Zambia being at the far extreme of 6.5 to 7.5 years. As men age, they tend to seek a mate who is younger. [ 64 ]


25% of  online dating  website  eHarmony 's male customers over the age of 50 request to only be matched with women younger than 40. [ 65 ]  The 2010 OkCupid study found that female desirability to its male users peaks at age 21, and falls below the average for all women at 31. After age 26, men have a larger potential dating pool than women on the site; and by age 48, their pool is almost twice as large. The median 31-year-old male user searches for women aged 22-to-35, while the median 42-year-old male searches for women 27-to-45. The age skew is even greater with messages to other users; the median 30-year-old male messages teenage girls as often as women his own age, while mostly ignoring women a few years older than him. Excluding the 10% most and 10% least beautiful women, women's attractiveness does not change between 18 and 40. If extremes are included, however, "there's no doubt that younger [women] are more physically attractive – indeed in many ways beauty and youth are inextricable. That's why most of the models you see in magazines are teenagers". [ 58 ]


Pheromones  (detected by female hormone markers) reflect female fertility and the  reproductive value  mean. [ 66 ]  As females age, the  estrogen -to- androgen  production ratio changes and results in female faces to appear more masculine (thus appearing less "attractive"). [ 66 ]  In a small (n=148) study performed in the United States, using male college students at one university, the mean age expressed as ideal for a wife was found to be 16.87 years old, while 17.76 was the mean ideal age for a brief sexual encounter. However, the study sets up a framework where "taboos against sex with young girls" are purposely diminished, and biased their sample by removing any participant over the age of 30, with a mean participant age of 19.83. [ 67 ]  In a study of  penile tumescence , men were found most aroused by pictures of young adult females. [ 68 ]


Signals of fertility in women are often also seen as signals of youth. The evolutionary perspective proposes the idea that when it comes to sexual reproduction, the minimal parental investment required by men gives them the ability and desire to simply reproduce 'as much as possible.' [ 69 ]  It therefore makes sense that men are attracted to the features in women which signal youthfulness, and thus fertility. [ 69 ]  Their chances of reproductive success are much higher than they would be should they pair with someone older—and therefore less fertile.


This may explain why combating age declines in attractiveness occurs from a younger age in women than in men. For example, the  removal of one's body hair  is considered a very feminine thing to do. [ 70 ]  This can be explained by the fact that aging results in raised levels of  testosterone  and thus, body hair growth. Shaving reverts one's appearance to a more youthful stage [ 70 ]  and although this may not be an honest signal, men will interpret this as a reflection of increased fertile value. Research supports this, showing hairlessness is considered sexually attractive by men. [ 71 ]


"Leg-to-body ratio" is seen as an indicator of physical attractiveness but there appears to be no single accepted definition of leg-length: the 'perineum-to-floor' measure [ b ]  is the most frequently used, but arguably the distance from the ankle bone to the outer hip bone is more rigorous. [ 73 ]  With the latter metric, the most attractive male leg-to-body ratio (judged by American women) is 1:1. [ 73 ]  A Japanese study using the former metric found the same result for male attractiveness, but women with longer legs than the rest of their body were judged to be more attractive. [ 74 ]  Excessive deviations from the mean were seen as indicative of disease. [ 74 ]  A study using Polish participants found that legs 5% longer than the average for both sexes was considered most attractive. [ 75 ]  The study concluded this preference might stem from the influence of long-legged  runway models . [ 76 ]  Another study using British and American participants found "mid-ranging" leg-to-body ratios to be most ideal. [ 77 ]


A study by Swami et al. of British male and female undergraduates showed a preference for men with legs as long as the rest of their body and women with 40% longer legs than the rest of their body. [ 72 ]  The researcher concluded that this preference might be influenced by American culture, in which long-legged women are portrayed as more attractive. [ 72 ]