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Sexual arousal (also known as sexual excitement) describes the
physiological and psychological responses in preparation for
sexual intercourse or when exposed to
sexual stimuli
Sexual stimulation is any stimulus (including bodily contact) that leads to, enhances and maintains sexual arousal, and may lead to orgasm. Although sexual arousal may arise without physical stimulation, achieving orgasm usually requires physic ...
. A number of physiological responses occur in the body and mind as preparation for sexual intercourse, and continue during intercourse.
Male arousal will lead to an
erection, and in
female arousal the body's response is engorged sexual tissues such as
nipples
The nipple is a raised region of tissue on the surface of the breast from which, in females, milk leaves the breast through the lactiferous ducts to feed an infant. The milk can flow through the nipple passively or it can be ejected by smooth m ...
,
vulva
The vulva (plural: vulvas or vulvae; derived from Latin for wrapper or covering) consists of the external female sex organs. The vulva includes the mons pubis (or mons veneris), labia majora, labia minora, clitoris, vestibular bulbs, vulv ...
,
clitoris,
vaginal walls, and
vaginal lubrication
Vaginal lubrication is a naturally produced fluid that lubricates a
vagina. Vaginal lubrication is always present, but production increases significantly near ovulation and during sexual arousal in anticipation of sexual intercourse. Vaginal ...
.
Mental stimuli and
physical stimuli such as touch, and the internal fluctuation of
hormones, can influence sexual arousal.
Sexual arousal has several stages and may not lead to any actual sexual activity beyond a mental arousal and the physiological changes that accompany it. Given sufficient sexual stimulation, sexual arousal reaches its climax during an
orgasm
Orgasm (from Greek , ; "excitement, swelling") or sexual climax is the sudden discharge of accumulated sexual excitement during the sexual response cycle, resulting in rhythmic, involuntary muscular contractions in the pelvic region chara ...
. It may also be pursued for its own sake, even in the absence of an orgasm.
Erotic stimuli
Depending on the situation, a person can be sexually aroused by a variety of factors, both physical and mental. A person may be sexually aroused by another person or by particular aspects of that person, or by a non-human object. The physical stimulation of an
erogenous zone
An erogenous zone (from Greek , ''érōs'' "love"; and English ''-genous'' "producing", from Greek , ''-genḗs'' "born") is an area of the human body that has heightened sensitivity, the stimulation of which may generate a sexual response, s ...
or acts of
foreplay
Foreplay is a set of emotionally and physically intimate acts between one or more people meant to create sexual arousal and desire for sexual activity. Although foreplay is typically understood as physical sexual activity, nonphysical activiti ...
can result in arousal, especially if it is accompanied with the anticipation of imminent sexual activity. Sexual arousal may be assisted by a
romantic setting, music or other soothing situation. The potential stimuli for sexual arousal vary from person to person, and from one time to another, as does the level of arousal.
Stimuli can be classified according to the sense involved:
somatosensory
In physiology, the somatosensory system is the network of neural structures in the brain and body that produce the perception of touch (haptic perception), as well as temperature (thermoception), body position (proprioception), and pain. It i ...
(touch), visual, and
olfactory (scent).
Auditory stimuli are also possible, though they are generally considered secondary in role to the other three. Erotic stimuli which can result in sexual arousal can include conversation, reading, films or images, or a smell or setting, any of which can generate erotic thoughts and memories in a person. Given the right context, these may lead to the person desiring physical contact, including
kiss
A kiss is the touch or pressing of one's lips against another person or an object. Cultural connotations of kissing vary widely. Depending on the culture and context, a kiss can express sentiments of love, passion, romance, sexual attraction, ...
ing,
cuddling, and
petting of an erogenous zone. This may in turn make the person desire direct sexual stimulation of the
breast
The breast is one of two prominences located on the upper ventral region of a primate's torso. Both females and males develop breasts from the same embryological tissues.
In females, it serves as the mammary gland, which produces and sec ...
s,
nipple
The nipple is a raised region of tissue on the surface of the breast from which, in females, milk leaves the breast through the lactiferous ducts to feed an infant. The milk can flow through the nipple passively or it can be ejected by smooth m ...
s,
buttocks
The buttocks (singular: buttock) are two rounded portions of the exterior anatomy of most mammals, located on the posterior of the pelvic region. In humans, the buttocks are located between the lower back and the perineum. They are composed ...
and/or
genitals
A sex organ (or reproductive organ) is any part of an animal or plant that is involved in sexual reproduction. The reproductive organs together constitute the reproductive system. In animals, the testis in the male, and the ovary in the female, a ...
, and further
sexual activity
Human sexual activity, human sexual practice or human sexual behaviour is the manner in which humans experience and express their sexuality. People engage in a variety of sexual acts, ranging from activities done alone (e.g., masturbation) ...
.
Erotic stimuli may originate from a source unrelated to the object of subsequent sexual interest. For example, many people may find
nudity,
erotica
Erotica is literature or art that deals substantively with subject matter that is erotic, sexually stimulating or sexually arousing. Some critics regard pornography as a type of erotica, but many consider it to be different. Erotic art may use ...
or
pornography sexually arousing. This may generate a general sexual interest that is satisfied by sexual activity. When sexual arousal is achieved by or dependent on the use of objects, it is referred to as
sexual fetishism, or in some instances a
paraphilia
Paraphilia (previously known as sexual perversion and sexual deviation) is the experience of intense sexual arousal to atypical objects, situations, fantasies, behaviors, or individuals. It has also been defined as sexual interest in anything ot ...
.
There is a common belief that women need more time to achieve arousal. However, recent scientific research has shown that there is no considerable difference for the time men and women require to become fully aroused. Scientists from
McGill University Health Centre
The McGill University Health Centre (MUHC; french: Centre universitaire de santé McGill) is one of two major healthcare networks in the city of Montreal, Quebec. It is affiliated with McGill University and is one of the largest medical complex in ...
in
Montreal
Montreal ( ; officially Montréal, ) is the second-most populous city in Canada and most populous city in the Canadian province of Quebec. Founded in 1642 as '' Ville-Marie'', or "City of Mary", it is named after Mount Royal, the triple ...
(in Canada) used the method of
thermal imaging
Infrared thermography (IRT), thermal video and/or thermal imaging, is a process where a thermal camera captures and creates an image of an object by using infrared radiation emitted from the object in a process, which are examples of infrared i ...
to record baseline
temperature
Temperature is a physical quantity that expresses quantitatively the perceptions of hotness and coldness. Temperature is measurement, measured with a thermometer.
Thermometers are calibrated in various Conversion of units of temperature, temp ...
change in genital area to define the time necessary for sexual arousal. Researchers studied the time required for an individual to reach the peak of sexual arousal while watching sexually explicit movies or pictures and came to the conclusion that on average women and men took almost the same time for sexual arousal — around 10 minutes.
[ The time needed for foreplay is strongly individual and varies from one occasion to the next depending on circumstances.]
Unlike many animals, human
Humans (''Homo sapiens'') are the most abundant and widespread species of primate, characterized by bipedalism and exceptional cognitive skills due to a large and complex brain. This has enabled the development of advanced tools, cultu ...
s do not have a mating season
Seasonal breeders are animal species that successfully mate only during certain times of the year. These times of year allow for the optimization of survival of young due to factors such as ambient temperature, food and water availability, and ch ...
, and both sexes are potentially capable of sexual arousal throughout the year.
Disorders
Sexual arousal for most people is a positive experience and an aspect of their sexuality, and is often sought. A person can normally control how they will respond to arousal. They will normally know what things or situations are potentially stimulating, and may at their leisure decide to either create or avoid these situations. Similarly, a person's sexual partner will normally also know their partner's erotic stimuli and turn-offs. Some people feel embarrassed by sexual arousal and some are sexually inhibited. Some people do not feel aroused on every occasion that they are exposed to erotic stimuli, nor act in a sexual way on every arousal. A person can take an active part in a sexual activity without sexual arousal. These situations are considered normal, but depend on the maturity, age, culture and other factors influencing the person.
However, when a person fails to be aroused in a situation that would normally produce arousal and the lack of arousal is persistent, it may be due to a sexual arousal disorder or hypoactive sexual desire disorder. There are many reasons why a person fails to be aroused, including a mental disorder, such as depression, drug use, or a medical or physical condition. The lack of sexual arousal may be due to a general lack of sexual desire or due to a lack of sexual desire for the current partner. A person may always have had no or low sexual desire or the lack of desire may have been acquired during the person's life. There are also complex philosophical and psychological issues surrounding sexuality. Attitudes towards life, death, childbirth, one's parents, friends, family, contemporary society, the human race in general, and particularly one's place in the world play a substantive role in determining how a person will respond in any given sexual situation.
On the other hand, a person may be hypersexual
Hypersexuality is extremely frequent or suddenly increased libido. It is controversial whether it should be included as a clinical diagnosis used by mental healthcare professionals. Nymphomania and satyriasis were terms previously used for the c ...
, which is a desire to engage in sexual activities considered abnormally high in relation to normal development or culture, or suffering from a persistent genital arousal disorder
Persistent genital arousal disorder (PGAD), previously called persistent sexual arousal syndrome, is spontaneous, persistent, unwanted and uncontrollable genital arousal in the absence of sexual stimulation or sexual desire, and is typically not ...
, which is a spontaneous, persistent, and uncontrollable arousal, and the physiological changes associated with arousal.
Physiological and psychological response patterns
Physiological responses
Sexual arousal causes various physical responses, most significantly in the sex organ
A sex organ (or reproductive organ) is any part of an animal or plant that is involved in sexual reproduction. The reproductive organs together constitute the reproductive system. In animals, the testis in the male, and the ovary in the female, a ...
s (genital organs). Sexual arousal for a man is usually indicated by the swelling and erection of the penis
A penis (plural ''penises'' or ''penes'' () is the primary sexual organ that male animals use to inseminate females (or hermaphrodites) during copulation. Such organs occur in many animals, both vertebrate and invertebrate, but males d ...
when blood fills the corpus cavernosum. This is usually the most prominent and reliable sign of sexual arousal in males. In a woman, sexual arousal leads to increased blood flow to the clitoris and vulva
The vulva (plural: vulvas or vulvae; derived from Latin for wrapper or covering) consists of the external female sex organs. The vulva includes the mons pubis (or mons veneris), labia majora, labia minora, clitoris, vestibular bulbs, vulv ...
, as well as vaginal transudation - the seeping of moisture through the vaginal walls which serves as lubrication.
Male
It is normal to correlate the erection of the penis
A penis (plural ''penises'' or ''penes'' () is the primary sexual organ that male animals use to inseminate females (or hermaphrodites) during copulation. Such organs occur in many animals, both vertebrate and invertebrate, but males d ...
with male sexual arousal. Physical or psychological stimulation, or both, leads to vasodilation
Vasodilation is the widening of blood vessels. It results from relaxation of smooth muscle cells within the vessel walls, in particular in the large veins, large arteries, and smaller arterioles. The process is the opposite of vasoconstrictio ...
and the increased blood flow engorges the three spongy areas that run along the length of the penis (the two corpora cavernosa and the corpus spongiosum
The corpus spongiosum is the mass of spongy tissue surrounding the male urethra within the penis. It is also called the corpus cavernosum urethrae in older texts.
Anatomy
The proximal part of the corpus spongiosum is expanded to form the ure ...
). The penis grows enlarged and firm, the skin of the scrotum
The scrotum or scrotal sac is an anatomical male reproductive structure located at the base of the penis that consists of a suspended dual-chambered sac of skin and smooth muscle. It is present in most terrestrial male mammals. The scrotum co ...
is pulled tighter, and the testes
A testicle or testis (plural testes) is the male reproductive gland or gonad in all bilaterians, including humans. It is homologous to the female ovary. The functions of the testes are to produce both sperm and androgens, primarily testoste ...
are pulled up against the body. However, the relationship between erection and arousal is not one-to-one (arousal non-concordance). After their mid-forties, some men report that they do not always have an erection when they are sexually aroused. Equally, a male erection can occur during sleep (nocturnal penile tumescence
Nocturnal penile tumescence is a spontaneous erection of the penis during sleep or when waking up. Along with nocturnal clitoral tumescence, it is also known as sleep-related erection, morning glory or morning wood. Men without physiological erec ...
) without conscious sexual arousal or due to mechanical stimulation (e.g. rubbing against the bed sheet) alone. A young man—or one with a strong libido—may experience enough sexual arousal for an erection to result from a passing thought, or just the sight of a passerby. Once erect, his penis may gain enough stimulation from contact with the inside of his clothing to maintain and encourage it for some time.
As sexual arousal and stimulation continues, it is likely that the glans
The glans (, plural "glandes" ; from the Latin word for "acorn") is a vascular structure located at the tip of the penis in male mammals or a homologous genital structure of the clitoris in female mammals.
Structure
The exterior structure ...
or head of the erect penis will swell wider and, as the genitals become further engorged with blood, their color deepens and the testicles can grow up to 50% larger. As the testicles continue to rise, a feeling of warmth may develop around them and the perineum
The perineum in humans is the space between the anus and scrotum in the male, or between the anus and the vulva in the female. The perineum is the region of the body between the pubic symphysis (pubic arch) and the coccyx (tail bone), includi ...
. With further sexual stimulation, their heart rate increases, blood pressure rises and breathing becomes quicker. The increase in blood flow in the genital and other regions may lead to a sex flush in some men.
As sexual stimulation continues, orgasm
Orgasm (from Greek , ; "excitement, swelling") or sexual climax is the sudden discharge of accumulated sexual excitement during the sexual response cycle, resulting in rhythmic, involuntary muscular contractions in the pelvic region chara ...
begins, when the muscles of the pelvic floor
The pelvic floor or pelvic diaphragm is composed of muscle fibers of the levator ani, the coccygeus muscle, and associated connective tissue which span the area underneath the pelvis. The pelvic diaphragm is a muscular partition formed by the lev ...
, the vas deferens
The vas deferens or ductus deferens is part of the male reproductive system of many vertebrates. The ducts transport sperm from the epididymis to the ejaculatory ducts in anticipation of ejaculation. The vas deferens is a partially coiled tube ...
(between the testicles and the prostate), the seminal vesicle
The seminal vesicles (also called vesicular glands, or seminal glands) are a pair of two convoluted tubular glands that lie behind the urinary bladder of some male mammals. They secrete fluid that partly composes the semen.
The vesicles are 5 ...
s and the prostate
The prostate is both an accessory gland of the male reproductive system and a muscle-driven mechanical switch between urination and ejaculation. It is found only in some mammals. It differs between species anatomically, chemically, and phys ...
gland itself may begin to contract in a way that forces sperm and semen into the urethra
The urethra (from Greek οὐρήθρα – ''ourḗthrā'') is a tube that connects the urinary bladder to the urinary meatus for the removal of urine from the body of both females and males. In human females and other primates, the urethra c ...
inside the penis. Once this has started, it is likely that the man will continue to ejaculate
Ejaculation is the discharge of semen (the ''ejaculate''; normally containing sperm) from the male reproductory tract as a result of an orgasm. It is the final stage and natural objective of male sexual stimulation, and an essential componen ...
and orgasm fully, with or without further stimulation.
Equally, if sexual stimulation stops before orgasm, the physical effects of the stimulation, including the vasocongestion
Vasocongestion, vascular congestion or vascular engorgement is the swelling of bodily tissues caused by increased vascular blood flow and a localized increase in blood pressure. Typical causes of vasocongestion in humans includes menstruation, sexu ...
, will subside in a short time. Repeated or prolonged stimulation without orgasm and ejaculation can lead to discomfort in the testes (corresponding to the slang term "blue balls
Blue balls is slang for an uncomfortable testicular sensation that can occur during a state of male sexual arousal. The term is thought to have originated in the United States, first appearing in 1916. Another slang term used for the conditio ...
").
After orgasm and ejaculation, men usually experience a refractory period characterized by loss of their erection, a subsidence in any sex flush, less interest in sexual activity, and a feeling of relaxation that can be attributed to the neurohormone A neurohormone is any hormone produced and released by neuroendocrine cells (also called neurosecretory cells) into the blood. By definition of being hormones, they are secreted into the circulation for systemic effect, but they can also have a role ...
s oxytocin and prolactin
Prolactin (PRL), also known as lactotropin, is a protein best known for its role in enabling mammals to produce milk. It is influential in over 300 separate processes in various vertebrates, including humans. Prolactin is secreted from the pit ...
. The intensity and duration of the refractory period can be very short in a highly aroused young man in a highly arousing situation, perhaps without even a noticeable loss of erection. It can be as long as a few hours or days in middle-aged and older men.
Female
The beginnings of sexual arousal in a woman's body is usually marked by vaginal lubrication
Vaginal lubrication is a naturally produced fluid that lubricates a
vagina. Vaginal lubrication is always present, but production increases significantly near ovulation and during sexual arousal in anticipation of sexual intercourse. Vaginal ...
(wetness; though this can occur without arousal due to infection or cervical mucus production around ovulation), swelling and engorgement of the external genitals, and internal lengthening and enlargement of the vagina
In mammals, the vagina is the elastic, muscular part of the female genital tract. In humans, it extends from the vestibule to the cervix. The outer vaginal opening is normally partly covered by a thin layer of mucosal tissue called the hymen ...
. There have been studies to find the degree of correlation between these physiological responses and the woman's subjective sensation of being sexually aroused: the findings usually are that in some cases there is a high correlation, while in others, it is surprisingly low.
Further stimulation can lead to further vaginal wetness and further engorgement and swelling of the clitoris and the labia
The labia are part of the female genitalia; they are the major externally visible portions of the vulva. In humans, there are two pairs of labia: the ''labia majora'' (or the outer labia) are larger and thicker, while the '' labia minora'' are fo ...
, along with increased redness or darkening of the skin in these areas as blood flow increases. Further changes to the internal organs also occur including to the internal shape of the vagina and to the position of the uterus
The uterus (from Latin ''uterus'', plural ''uteri'') or womb () is the organ in the reproductive system of most female mammals, including humans that accommodates the embryonic and fetal development of one or more embryos until birth. The ...
within the pelvis. Other changes include an increase in heart rate
Heart rate (or pulse rate) is the frequency of the heartbeat measured by the number of contractions (beats) of the heart per minute (bpm). The heart rate can vary according to the body's physical needs, including the need to absorb oxygen and excr ...
as well as in blood pressure, feeling hot and flushed and perhaps experiencing tremors. A sex flush may extend over the chest and upper body.
If sexual stimulation continues, then sexual arousal may peak into orgasm
Orgasm (from Greek , ; "excitement, swelling") or sexual climax is the sudden discharge of accumulated sexual excitement during the sexual response cycle, resulting in rhythmic, involuntary muscular contractions in the pelvic region chara ...
. After orgasm, some women do not want any further stimulation and the sexual arousal quickly dissipates. Suggestions have been published for continuing the sexual excitement and moving from one orgasm into further stimulation and maintaining or regaining a state of sexual arousal that can lead to second and subsequent orgasms. Some women have experienced such multiple orgasms quite spontaneously.
While young women may become sexually aroused quite easily, and reach orgasm relatively quickly with the right stimulation in the right circumstances, there are physical and psychological changes to women's sexual arousal and responses as they age. Older women produce less vaginal lubrication and studies have investigated changes to degrees of satisfaction, frequency of sexual activity, to desire, sexual thoughts and fantasies
Fantasy is a genre of fiction.
Fantasy, Fantasie, or Fantasies may also refer to:
Arts and entertainment Music
* Fantasia (music), a free-form musical composition
* ''Fantasie'' (Widmann), a 1993 composition for solo clarinet by Jörg Widmann
* ...
, sexual arousal, beliefs about and attitudes to sex, pain, and the ability to reach orgasm in women in their 40s and after menopause
Menopause, also known as the climacteric, is the time in women's lives when menstrual periods stop permanently, and they are no longer able to bear children. Menopause usually occurs between the age of 47 and 54. Medical professionals often ...
. Other factors have also been studied including socio-demographic variables, health, psychological variables, partner variables such as their partner's health or sexual problems, and lifestyle variables. It appears that these other factors often have a greater impact on women's sexual functioning than their menopausal status. It is therefore seen as important always to understand the "context of women's lives" when studying their sexuality.
Reduced estrogen
Estrogen or oestrogen is a category of sex hormone responsible for the development and regulation of the female reproductive system and secondary sex characteristics. There are three major endogenous estrogens that have estrogenic hormonal ac ...
levels may be associated with increased vaginal dryness and less clitoral erection
Clitoral erection is a physiological phenomenon where the clitoris becomes enlarged and firm.
Clitoral erection is the result of a complex interaction of psychological, neural, vascular, and endocrine factors, and is usually, though not exclu ...
when aroused, but are not directly related to other aspects of sexual interest or arousal. In older women, decreased pelvic muscle tone may mean that it takes longer for arousal to lead to orgasm, may diminish the intensity of orgasms, and then cause more rapid resolution. The uterus typically contracts during orgasm and, with advancing age, those contractions may actually become painful.
Psychological responses
Psychological sexual arousal involves appraisal and evaluation of a stimulus, categorization of a stimulus as sexual, and an affective response. The combination of cognitive and physiological states elicits psychological sexual arousal. Some suggest that psychological sexual arousal results from an interaction of cognitive and experiential factors, such as affective state, previous experience, and current social context.
Male
The relationship between sexual desire
Sexual desire is an emotion and motivational state characterized by an interest in sexual objects or activities, or by a drive to seek out sexual objects or to engage in sexual activities. It is an aspect of sexuality, which varies significantly f ...
and arousal in men is complex, with a wide range of factors increasing or decreasing sexual arousal. Physiological responses, such as heart rate
Heart rate (or pulse rate) is the frequency of the heartbeat measured by the number of contractions (beats) of the heart per minute (bpm). The heart rate can vary according to the body's physical needs, including the need to absorb oxygen and excr ...
, blood pressure, and erection, are often discordant with self-reported subjective perceptions of arousal. This inconsistency suggests that psychological or cognitive aspects also have a strong effect on sexual arousal. The cognitive aspects of sexual arousal in men are not completely known, but the state does involve the appraisal and evaluation of the stimulus, categorization of the stimulus as sexual, and an affective response. Research suggests that cognitive factors, such as sexual motivation, perceived gender role
A gender role, also known as a sex role, is a social role encompassing a range of behaviors and attitudes that are generally considered acceptable, appropriate, or desirable for a person based on that person's sex. Gender roles are usually cent ...
expectations, and sexual attitudes, contribute to sex differences observed in subjective sexual arousal. Specifically, while watching heterosexual erotic videos, men are more influenced by the sex of the actors portrayed in the stimulus, and men may be more likely than women to objectify the actors. There are reported differences in brain activation to sexual stimuli, with men showing higher levels of amygdala
The amygdala (; plural: amygdalae or amygdalas; also '; Latin from Greek, , ', 'almond', 'tonsil') is one of two almond-shaped clusters of nuclei located deep and medially within the temporal lobes of the brain's cerebrum in complex verte ...
and hypothalamic responses than women. This suggests the amygdala plays a critical role in the processing of sexually arousing visual stimuli in men.
Female
Research suggests that cognitive factors like sexual motivation, perceived gender role
A gender role, also known as a sex role, is a social role encompassing a range of behaviors and attitudes that are generally considered acceptable, appropriate, or desirable for a person based on that person's sex. Gender roles are usually cent ...
expectations, and sexual attitudes play important roles in women's self-reported levels of sexual arousal. In her alternative model of sexual response, Basson suggests that women's need for intimacy
An intimate relationship is an interpersonal relationship that involves physical or emotional intimacy. Although an intimate relationship is commonly a sexual relationship, it may also be a non-sexual relationship involving family, friends, or ...
prompts them to engage with sexual stimuli, which leads to an experience of sexual desire
Sexual desire is an emotion and motivational state characterized by an interest in sexual objects or activities, or by a drive to seek out sexual objects or to engage in sexual activities. It is an aspect of sexuality, which varies significantly f ...
and psychological sexual arousal. Psychological sexual arousal also has an effect on physiological mechanisms; Goldey and van Anders showed that sexual cognitions impact hormone levels in women, such that sexual thoughts result in a rapid increase in testosterone
Testosterone is the primary sex hormone and anabolic steroid in males. In humans, testosterone plays a key role in the development of male reproductive tissues such as testes and prostate, as well as promoting secondary sexual characteristi ...
in women who were not using hormonal contraception. In terms of brain activation, researchers have suggested that amygdala
The amygdala (; plural: amygdalae or amygdalas; also '; Latin from Greek, , ', 'almond', 'tonsil') is one of two almond-shaped clusters of nuclei located deep and medially within the temporal lobes of the brain's cerebrum in complex verte ...
responses are not solely determined by level of self-reported sexual arousal; Hamann and colleagues found that women self-reported higher sexual arousal than men, but experienced lower levels of amygdala responses.
Models of human sexual response
Human sexual response cycle
During the late 1950s and early 1960s, William H. Masters and Virginia E. Johnson conducted multiple studies into human sexuality
Human sexuality is the way people experience and express themselves sexually. This involves biological, psychological, physical, erotic, emotional, social, or spiritual feelings and behaviors. Because it is a broad term, which has varied ...
. In 1966, they published '' Human Sexual Response'', detailing four stages of physiological changes in humans during sexual stimulation: excitement, plateau, orgasm, and resolution.
Singer's model of sexual arousal
Barry Singer presented a model of the process of sexual arousal in 1984, in which he conceptualized human sexual response to be composed of ''three independent but generally sequential components''. The first stage, ''aesthetic response,'' is an emotional reaction to noticing an attractive face or figure. This emotional reaction produces an increase in attention toward the object of attraction, typically involving head and eye movements toward the attractive object. The second stage, ''approach response,'' progresses from the first and involves bodily movements towards the object. The final ''genital response'' stage recognizes that with both attention and closer proximity, physical reactions result in genital tumescence. Singer also stated that there is an array of other autonomic responses, but acknowledges that the research literature suggests that the genital response is ''the most reliable and convenient to measure'' in males.
Basson's sexual response cycle
In 2000, Rosemary Basson presented an alternative model to the human sexual response cycle that is ''specific to women’s sexual response''. She argues that gender differences in sex drive
Libido (; colloquial: sex drive) is a person's overall sexual drive or desire for sexual activity. Libido is influenced by biological, psychological, and social factors. Biologically, the sex hormones and associated neurotransmitters that act up ...
, sexual motivation, sexual concordance, and capacity for orgasm underlie the need for an alternative model of sexual response. While the human sexual response cycle begins with desire, followed by arousal, orgasm, and finally resolution, Basson's alternative model is circular and begins with women feeling a need for intimacy
An intimate relationship is an interpersonal relationship that involves physical or emotional intimacy. Although an intimate relationship is commonly a sexual relationship, it may also be a non-sexual relationship involving family, friends, or ...
, which leads her to seek out and be receptive to sexual stimuli; women then feel sexual arousal, in addition to sexual desire
Sexual desire is an emotion and motivational state characterized by an interest in sexual objects or activities, or by a drive to seek out sexual objects or to engage in sexual activities. It is an aspect of sexuality, which varies significantly f ...
. The cycle results in an enhanced feeling of intimacy. Basson emphasizes the idea that a lack of spontaneous desire should not be taken as an indication of female sexual dysfunction; many women experience sexual arousal and responsive desire simultaneously when they are engaged in sexual activity.
Toates's incentive-motivation model
Frederick Toates presented a model of sexual motivation, arousal, and behavior in 2009 that combines the principles of ''incentive-motivation theory'' and ''hierarchical control of behavior''. The basic incentive-motivation model of sex suggests that incentive cues in the environment invade the nervous system, which results in sexual motivation. Positive sexual experiences enhance motivation, while negative experiences reduce it. Motivation and behaviour are organized hierarchically; each are controlled by a combination direct (external stimuli) and indirect (internal cognitions) factors. Excitation and inhibition of behavior act at various levels of this hierarchical structure. For instance, an external stimulus may directly excite sexual arousal and motivation below a conscious level of awareness, while an internal cognition can elicit the same effects indirectly, through the conscious representation of a sexual image. In the case of inhibition, sexual behavior can be active or conscious (e.g., choosing not to have sex) or it can be passive or unconscious (e.g., being unable to have sex due to fear). Toates emphasizes the importance considering cognitive representations in addition to external stimuli; he suggests that mental representations of incentives are interchangeable with excitatory external stimuli for eliciting sexual arousal and motivation.
Bancroft and Janssen's dual control model
This model created by John Bancroft and Erick Janssen, previously at the Kinsey Institute, explores the ''individual variability of sexual response''. They postulate that this variability depends on the interaction between an individual's sexual excitation system (SES) and sexual inhibition system (SIS). Popularized by Emily Nagoski
Emily Nagoski (born 1977) is an American sex educator and researcher, and author of the book ''Come as You Are''. She is the former director of wellness education at Smith College, where she teaches a course on women's sexuality.
''Come as You A ...
's self-help book ''Come as You Are'', the SES has been described as the sexual response's 'accelerator' and the SIS as the 'brake'.[Nagoski, E. (2015). Come As You Are. New York City, New York: Simon and Schuster.] The SIS/SES questionnaire was developed to assess an individual's SIS and SES levels. A factor analysis
Factor analysis is a statistical method used to describe variability among observed, correlated variables in terms of a potentially lower number of unobserved variables called factors. For example, it is possible that variations in six observed ...
of the SIS/SES questionnaire, revealed a single excitation factor and two inhibition factors. These inhibition factors were interpreted as SIS1 (inhibition due to the threat of performance failure) and SIS2 (inhibition due to the threat of performance consequences).
The SIS/SES questionnaire was originally developed for men though it has since proven its statistical validity among women. Despite this, the SESII-W (the Sexual Excitation/Sexual Inhibition Inventory for Women) was created by Graham and associates. Female focus groups found that the context of the emotional relationship between sexual partners was not fully represented in the original SIS/SES questionnaire. A factor analysis of this questionnaire revealed only two factors: sexual excitation (SE) and sexual inhibition (SI). This may point to internal inconsistencies in the SIS/SES questionnaire regarding gender. One lower order factor in the SESII-W labeled Arousal Contingency was particularly relevant; this factor explains the easy disruption of sexual arousal.
Regardless of the difference in these two questionnaires, both surveys' scores show normal distribution verifying the hypothesis that there is a normal individual variation in sexual arousal and inhibition. In the original SIS/SES questionnaire, statistically significant gender differences are seen despite considerable overlap in scores between men and women. On average, males score higher on sexual excitation and lower than females on both facets of sexual inhibition. The differences in scores between genders have not been explained beyond the theoretical level.
The source of individual variability on the sexual excitation and inhibition systems is not known definitively. Even less is known about how these systems develop in individuals. Age of first masturbation has been used as a measure to assess sexual development. Age of masturbatory onset is much more variable in girls than boys, whose tend to be close to puberty.[Bancroft, J., Herbenick, D., & Reynolds, M. (2003). Masturbation as a marker of sexual development. In J. Bancroft (Ed.), Sexual development in childhood (pp. 156–185). Bloomington: Indiana University Press.] Researchers have not determined whether this gender difference is biological in nature or influenced by sociocultural values. One twin-study has found evidence for the heritability of both factors of SIS, but research suggests that SES variability is down to environmental factors.
The majority of studies investigating sexual functioning use heterosexual participants exclusively, limiting the generalizability of the dual control model. One study comparing heterosexual and gay men found that gay men had similar scores for SIS2, but scored significantly higher for SIS1 and SES. Heterosexual, lesbian, and bisexual women's scores on the SESII-W found that bisexual women scored higher on SES than the other groups and heterosexual women scored higher on the sexual inhibition factor than both the lesbian and bisexual women.[Sanders, S. A., Graham, C. A., & Milhausen, R. R. (2008c). exual orientation and SESII–W Unpublished raw data.] More studies need to be done using the dual control model to gain a more broad view of sexual orientation and sexual arousability.
Assessment of genital arousal
One way to study sexual arousal in women and men is to conduct sexual psychophysiological research in a laboratory setting. This field of research looks at physical sexual responses in addition to mental and emotional experiences of sexual arousal.
Experimental studies
Various hypotheses and theories have been propounded in order to establish the biological bases for sexual arousal in humans. Ivan Tarkhanov showed, in experiments on cutting and artificial emptying of the seminal vesicle
The seminal vesicles (also called vesicular glands, or seminal glands) are a pair of two convoluted tubular glands that lie behind the urinary bladder of some male mammals. They secrete fluid that partly composes the semen.
The vesicles are 5 ...
s, that the latter played the crucial role in the generation of sexual excitement in frogs. Proceeding from these experimental results, Tarkhanov put forward a hypothesis that filling and evacuation of the seminal vesicles were the main biological cause which led to sexual arousal and its disappearance in mammals and humans. Ever since Tarkhanov's findings demonstrated sexual arousal in frogs to result from the state of seminal vesicles, the attempted elucidation of their role in other animals' sexual behaviour has been the object of experimental effort. No generalisation has yet appeared, however. The study performed by Beach & Wilson (University of California, Berkeley
The University of California, Berkeley (UC Berkeley, Berkeley, Cal, or California) is a public land-grant research university in Berkeley, California. Established in 1868 as the University of California, it is the state's first land-grant u ...
) in 1964 discovered that these glands do not participate in the regulation of sexual arousal of male rats in the similar manner. Whether the regularity observed in frogs is applicable to humans remains unknown. Unambiguous experimental evidence for the existence of the Tarkhanov regularity in human sexual behaviour has never been obtained.
Another explanation of sexual arousal is offered by the approach which Kazimierz Imieliński calls the "psychohydraulic model of sexuality". This point of view likens human sexuality to a steam boiler, with biological processes or internal irritants creating sexual tension. If the level of this tension reaches threshold, sexual arousal occurs as the expression of necessity to let off steam. Gary F. Kelly (Clarkson University
Clarkson University is a private research university with its main campus in Potsdam, New York, and additional graduate program and research facilities in the New York Capital Region and Beacon, New York. It was founded in 1896 and has an e ...
) describes this model as follows:
The "psychohydraulic model of sexuality" has been formulated most definitely in psychoanalysis
PsychoanalysisFrom Greek: + . is a set of theories and therapeutic techniques"What is psychoanalysis? Of course, one is supposed to answer that it is many things — a theory, a research method, a therapy, a body of knowledge. In what might b ...
:
After a certain time, the same process begins anew. Such an approach assumes sexual arousal to be a spontaneous desire that appears periodically like sensations of hunger and thirst. Drawing a parallel between these sensations and sexual excitation is widely accepted now: "Everyone must experience sexuality in some way to survive. ... In this sense sex is a necessity of life, just as air, food, and warmth." And yet there is no empirical evidence in support of such a parallel, Imieliński says. Sensations of hunger and thirst occur due to certain states of physiological insufficiency. The feeling of hunger results from the lack of glucose, fats and amino acids in blood. The feeling of thirst occurs in response to reduction of the water content of tissues. None of similar states of physiological deficiency responsible for the periodical appearance of sexual arousal has been revealed in human sexuality.
Females
Sexual arousal in women is characterized by vasocongestion
Vasocongestion, vascular congestion or vascular engorgement is the swelling of bodily tissues caused by increased vascular blood flow and a localized increase in blood pressure. Typical causes of vasocongestion in humans includes menstruation, sexu ...
of the genital
A sex organ (or reproductive organ) is any part of an animal or plant that is involved in sexual reproduction. The reproductive organs together constitute the reproductive system. In animals, the testis in the male, and the ovary in the female, a ...
tissues, including internal and external areas (e.g., vaginal walls, clitoris, and labia
The labia are part of the female genitalia; they are the major externally visible portions of the vulva. In humans, there are two pairs of labia: the ''labia majora'' (or the outer labia) are larger and thicker, while the '' labia minora'' are fo ...
). There are a variety of methods used to assess genital sexual arousal in women. Vaginal photoplethysmography (VPG) can measure changes in vaginal blood volume or phasic changes in vasocongestion associated with each heartbeat. Clitoral photoplethysmograph
Clitoral photoplethysmography uses light to measure clitoral blood volume (CBV).
A clitoral photoplethysmograph is a small clear acrylic device that contains a light source, and a light detector. The light source illuminates the capillary bed o ...
y functions in a similar way to VPG, but measures changes in clitoral blood volume, rather than vaginal vasocongestion. Thermography
Infrared thermography (IRT), thermal video and/or thermal imaging, is a process where a thermal camera captures and creates an image of an object by using infrared radiation emitted from the object in a process, which are examples of infrared i ...
provides a direct measure of genital sexual arousal by measuring changes in temperature
Temperature is a physical quantity that expresses quantitatively the perceptions of hotness and coldness. Temperature is measurement, measured with a thermometer.
Thermometers are calibrated in various Conversion of units of temperature, temp ...
associated with increased blood flow to the external genital tissues. Similarly, labial thermistor clip
The labial thermistor clip is a device used measure the skin temperature of the labia minora and is associated blood engorgement. This device consists of a thermistor affixed to a small metal clip that can be attached to the labia minora. The labia ...
s measure changes in temperature associated with genital engorgement; this method directly measures changes in temperature of the labia. More recently, laser doppler imaging
Laser Doppler imaging (LDI) is an imaging method that uses a laser beam to scan live tissue. When the laser light reaches the tissue, the moving blood cells generate doppler components in the reflected ( backscattered) light. The light that comes ...
(LDI) has been used as a direct measure of genital sexual arousal in women. LDI functions by measuring superficial changes in blood flow in the vulvar tissues.
Males
The most obvious response involved with sexual behaviour in males is penile erection
An erection (clinically: penile erection or penile tumescence) is a physiological phenomenon in which the penis becomes firm, engorged, and enlarged. Penile erection is the result of a complex interaction of psychological, neural, vascular, ...
. The use of the volume (or circumference) change during penile erection as a convenient measure of sexual arousal was first developed by Kurt Freund
Kurt Freund (17 January 1914 – 23 October 1996) was a Czech-Canadian physician and sexologist best known for developing the penile plethysmograph (a measurement of sexual arousal in males), research studies in pedophilia, and for the "courts ...
. This measurement of blood flow to the male genitals is known as penile plethysmography. This is commonly measured using a strain gauge, a simple mercury strain gauge encompassed in a ring of rubber. The ring surrounds the penis
A penis (plural ''penises'' or ''penes'' () is the primary sexual organ that male animals use to inseminate females (or hermaphrodites) during copulation. Such organs occur in many animals, both vertebrate and invertebrate, but males d ...
, but does not constrict or cause discomfort. The measure has been found by some to be a reliable and valid measurement of male arousal. More recently, thermography
Infrared thermography (IRT), thermal video and/or thermal imaging, is a process where a thermal camera captures and creates an image of an object by using infrared radiation emitted from the object in a process, which are examples of infrared i ...
has been developed to measure the physiological measurements of sexual arousal. Studies have found temperature change specific to the genitals during sexual arousal, which supports the validity of this measure.
Category-specificity
Category-specificity refers to a person showing sexual arousal to the categories of people they prefer to have sex with. Sexual arousal studies involving category-specificity look at genital responses (physiological changes), as well as subjective responses (what people report their arousal levels to be). Category-specific sexual arousal is more commonly found amongst men than women. Heterosexual
Heterosexuality is romantic attraction, sexual attraction or sexual behavior between people of the opposite sex or gender. As a sexual orientation, heterosexuality is "an enduring pattern of emotional, romantic, and/or sexual attractions" ...
men experience much higher genital and subjective arousal to women than to men. This pattern is reversed for homosexual men.
Studies have found that women have a non-category-specific genital response pattern of sexual arousal, meaning their genital responses are only modestly related to their preferred category. On the other hand, female subjective responses are category-specific, because they typically report their highest level of arousal to their preferred stimulus, although the reported difference in levels of arousal is typically much smaller than those in men. A possible explanation for the non-category specific genital arousal in women, which also accounts for their high individual variation, is the "preparation hypothesis". This hypothesis suggests that, provided there is enough of an increase in vaginal blood flow for vaginal lubrication
Vaginal lubrication is a naturally produced fluid that lubricates a
vagina. Vaginal lubrication is always present, but production increases significantly near ovulation and during sexual arousal in anticipation of sexual intercourse. Vaginal ...
to occur in a sexual context, the magnitude of arousal need not be consistent. That is, the hypothesis is that vaginal lubrication can take place as a protective mechanism even in a non-preferred sexual situation, such as when sexual activity is non-consensual
Consent occurs when one person voluntarily agrees to the proposal or desires of another. It is a term of common speech, with specific definitions as used in such fields as the law, medicine, research, and sexual relationships. Consent as und ...
.
Other researchers argue that since the research is done on people who volunteer to be studied, the observed levels of category specificity may not represent the population, that there may be different cultural expectations of sexual interests being linked to genital arousal that make men with non-category specific genital arousal less likely to appear as test subjects. There researchers also argue that the assumption that men are always sexually interested in what causes genital arousal removes its own falsifiability by explaining all contradictory data away as "denial", making the theory untestable.
Overlapping brain variables and sexual arousal
While there is disagreement among neurologists on whether or not it is possible to categorically distinguish male brains and female brains by measuring many variables in the brain, neurologists agree that all single variables in the brain display more individual variation and overlap between the sexes than differences between the sexes. For instance, men and women alike are capable of classifying sex acts as sexual no matter if they find them appealing or not, making a genital response to unappealing erotic stimuli a single mechanism step. It is therefore argued by neurologists that category specificity of genital response to erotical imagery, being determined by one or a small number of closely linked brain mechanisms and therefore not subject to significant multivariate effects, cannot be subject to such a large sex difference as that apparent in pletysmographic studies. These neurologists cite the existence of significant volunteering bias among men but not women in erotica research, in particular that the overrepresentation of erectile dysfunction yet underrepresentation of sexuality-related shame in volunteers is consistent with the hypothesis that genital response to both sexual relevance and appeal allows for a stronger erectile function than response only to appeal and that a majority of the male population are ashamed of their responses to unappealing stimuli, accounting for the discrepancy between the report from most heterosexual couples that male erection is faster than female lubrication and the appearance on pletysmography volunteers that female lubrication is at least as fast as male erection. They also argue that the appearance of a greater individual variability in female genital response than in male genital response is consistent with a representative female sample and a male sample subject to bias that leaves much of the individual variability unstudied, with a reference to the neurological observation that all brain structures display significant individual variability in both sexes and that no brain structure is variable only in females and not in males.
Arousal concordance and non-concordance
Sexual arousal results in a combination of physiological and psychological factors, like genital sexual response and subjective experience of sexual arousal. The degree to which genital and subjective sexual response correspond is termed ''concordance''.
Arousal non-concordance is when there is no link, for example in morning erection which happens both with men (Nocturnal penile tumescence
Nocturnal penile tumescence is a spontaneous erection of the penis during sleep or when waking up. Along with nocturnal clitoral tumescence, it is also known as sleep-related erection, morning glory or morning wood. Men without physiological erec ...
) and women (Nocturnal clitoral tumescence
Nocturnal clitoral tumescence (NCT), colloquially known as morning bean, is a spontaneous swelling of the clitoris during sleep or when waking up. Similar to the process in males, nocturnal penile tumescence, females experience clitoris tumescen ...
), or in cases of rape
Rape is a type of sexual assault usually involving sexual intercourse or other forms of sexual penetration carried out against a person without their consent. The act may be carried out by physical force, coercion, abuse of authority, or ...
where research confirms reports of an arousal non-concordance orgasm or orgasm alike event can take place - presumably as a measure to protect the internal organs of the vagina.
Research has shown a reliable gender difference in concordance of sexual arousal, such that men have a higher level of concordance between genital and subjective sexual responding than women do. Some researchers argue that this gender difference can be attributed to the type of method used to assess genital responding in women. There may be a difference in women's ability to perceive internal
Internal may refer to:
*Internality as a concept in behavioural economics
*Neijia, internal styles of Chinese martial arts
*Neigong or "internal skills", a type of exercise in meditation associated with Daoism
*''Internal (album)'' by Safia, 2016
...
versus external genital engorgement subjectively, as measured by vaginal photoplethysmography (VPG) and thermography
Infrared thermography (IRT), thermal video and/or thermal imaging, is a process where a thermal camera captures and creates an image of an object by using infrared radiation emitted from the object in a process, which are examples of infrared i ...
respectively. Chivers and colleagues found that men's and women's concordance was more similar when thermography was used as a measure of genital sexual arousal than when VPG was used. However, few studies using thermography have been conducted and further research is required to determine whether the gender difference in concordance is a measurement artifact or a true phenomenon.
Hormones
Several hormone
A hormone (from the Greek participle , "setting in motion") is a class of signaling molecules in multicellular organisms that are sent to distant organs by complex biological processes to regulate physiology and behavior. Hormones are require ...
s affect sexual arousal, including testosterone
Testosterone is the primary sex hormone and anabolic steroid in males. In humans, testosterone plays a key role in the development of male reproductive tissues such as testes and prostate, as well as promoting secondary sexual characteristi ...
, cortisol, and estradiol
Estradiol (E2), also spelled oestradiol, is an estrogen steroid hormone and the major female sex hormone. It is involved in the regulation of the estrous and menstrual female reproductive cycles. Estradiol is responsible for the development o ...
. However, the specific roles of these hormones are not clear.[Bancroft, J.,]
The endocrinology of sexual arousal
, "Journal of Endocrinology, 2005 Testosterone is the most commonly studied hormone involved with sexuality. It plays a key role in sexual arousal in males, with strong effects on central arousal mechanisms. The connection between testosterone and sexual arousal is more complex in females. Research has found testosterone levels increase as a result of sexual cognitions in females that do not use hormonal contraception. Also, women who participate in polyandrous
Polyandry (; ) is a form of polygamy in which a woman takes two or more husbands at the same time. Polyandry is contrasted with polygyny, involving one male and two or more females. If a marriage involves a plural number of "husbands and wive ...
relationships have higher levels of testosterone. However, it is unclear whether higher levels of testosterone cause increased arousal and in turn multiple partners or whether sexual activity with multiple partners cause the increase in testosterone. Inconsistent study results point to the idea that while testosterone may play a role in the sexuality of some women, its effects can be obscured by the co-existence of psychological or affective factors in others.
Other animals
While human sexuality is well understood, scientists do not completely grasp how other animals relate sexually. However, current research studies suggest that many animals, like humans, enjoy sexual relations that are not limited to reproduction. Dolphin
A dolphin is an aquatic mammal within the infraorder Cetacea. Dolphin species belong to the families Delphinidae (the oceanic dolphins), Platanistidae (the Indian river dolphins), Iniidae (the New World river dolphins), Pontoporiidae (the ...
s and bonobos, for example, are both well known to use sex as a "social tool to strengthen and maintain bonds". Ethologists
Ethology is the scientific study of animal behaviour, usually with a focus on behaviour under natural conditions, and viewing behaviour as an evolutionarily adaptive trait. Behaviourism as a term also describes the scientific and objectiv ...
have long documented the exchanges of sex to promote group cohesion in social animals
Sociality is the degree to which individuals in an animal population tend to associate in social groups (gregariousness) and form cooperative societies.
Sociality is a survival response to evolutionary pressures. For example, when a mother wasp ...
. Cementing social bondage is one of the most prominent theorized selective advantages of group selection
Group selection is a proposed mechanism of evolution in which natural selection acts at the level of the group, instead of at the level of the individual or gene.
Early authors such as V. C. Wynne-Edwards and Konrad Lorenz argued that the behavi ...
theory. Experts in the evolution of sex
Sexual reproduction is an adaptive feature which is common to almost all multicellular organisms and various unicellular organisms, with some organisms being incapable of asexual reproduction. Currently the adaptive advantage of sexual repro ...
such as John Maynard Smith
John Maynard Smith (6 January 1920 – 19 April 2004) was a British theoretical and mathematical evolutionary biologist and geneticist. Originally an aeronautical engineer during the Second World War, he took a second degree in genetics un ...
advocate for the idea that the exchange of sexual favors helps congeal and localize the assortment of alleles
An allele (, ; ; modern formation from Greek ἄλλος ''állos'', "other") is a variation of the same sequence of nucleotides at the same place on a long DNA molecule, as described in leading textbooks on genetics and evolution.
::"The chrom ...
in isolated population and therefore is potentially a very strong force in evolution
Evolution is change in the heritable characteristics of biological populations over successive generations. These characteristics are the expressions of genes, which are passed on from parent to offspring during reproduction. Variation ...
. Smith has also written extensively on the "seminal fluid swapping theory" logistic application of the assortment of alleles as a more accurate synthetic depiction of the Hardy–Weinberg principle
In population genetics, the Hardy–Weinberg principle, also known as the Hardy–Weinberg equilibrium, model, theorem, or law, states that allele and genotype frequencies in a population will remain constant from generation to generation in t ...
in cases of severely interbreeding populations.
Evolutionary models
The effect of sexual response is thought to be a plastic positive reinforcement behavior modifier associated with the Baldwin effect
In evolutionary biology, the Baldwin effect, a phenotype-first theory of evolution, describes the effect of learned behaviour on evolution. James Mark Baldwin and others suggested during the eclipse of Darwinism in the late 19th century that an ...
. The display of secondary sex characteristic
Secondary sex characteristics are features that appear during puberty in humans, and at sexual maturity in other animals. These characteristics are particularly evident in the sexually dimorphic phenotypic traits that distinguish the sexes of a s ...
s in humans such as a penis-like enlarged clitoris in females during arousal and gynecomastia
Gynecomastia (also spelled gynaecomastia) is the abnormal non-cancerous enlargement of one or both breasts in males due to the growth of breast tissue as a result of a hormone imbalance between estrogens and androgens. Updated by Brent Wisse ( ...
in males are thought to have once been objects of mate selection
Mate choice is one of the primary mechanisms under which evolution can occur. It is characterized by a "selective response by animals to particular stimuli" which can be observed as behavior.Bateson, Paul Patrick Gordon. "Mate Choice." Mate Choic ...
in human evolution because of the persistence of the phenomenon of these features invoking sexual arousal for potential mates in cross-cultural studies
Cross-cultural studies, sometimes called holocultural studies or comparative studies, is a specialization in anthropology and sister sciences such as sociology, psychology, economics, political science that uses field data from many societies th ...
. A dramatic example of this is the high rates of secondary sex characteristic dimorphism in some Southeast Asia human populations. Similar evolutionary stimuli may also have resulted in novel structures such as the pseudo-penis A pseudo-penis is any structure found on an animal that, while superficially appearing to be a penis, is derived from a different developmental path.
Mammals
In mammals, all intact developmentally typical males have a penis, but the clitoris in ...
of the female spotted hyena.
See also
* Aphrodisiac
An aphrodisiac is a substance that increases sexual desire, sexual attraction, sexual pleasure, or sexual behavior. Substances range from a variety of plants, spices, foods, and synthetic chemicals. Natural aphrodisiacs like cannabis or cocai ...
* Erectile tissue Erectile tissue is tissue in the body with numerous vascular spaces, or cavernous tissue, that may become engorged with blood. However, tissue that is devoid of or otherwise lacking erectile tissue (such as the labia minora, the vestibule/vagina and ...
* Kinsey Reports
* Nudity and sexuality Nudity is one of the physiological characteristics of humans, who alone among primates evolved to be effectively hairless. Human sexuality includes the physiological, psychological, and social aspects of sexual feelings and behaviors. In many socie ...
* Priapism
Priapism is a condition in which a penis remains erect for hours in the absence of stimulation or after stimulation has ended. There are three types: ischemic (low-flow), nonischemic (high-flow), and recurrent ischemic (intermittent). Most cases ...
* Sexology
* Sexual frustration
Sexual frustration is a sense of dissatisfaction stemming from a discrepancy between a person's desired and achieved Human sexual activity, sexual activity. It may result from impotence, physical, human sexuality#Psychological aspects, mental, sex ...
References
External links
*
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