Sexual arousal
Encyclopedia
Arousal
Arousal is a physiological and psychological state of being awake or reactive to stimuli. It involves the activation of the reticular activating system in the brain stem, the autonomic nervous system and the endocrine system, leading to increased heart rate and blood pressure and a condition of...
of sexual desire, during or in anticipation of sexual activity. Things that precipitate human sexual arousal are called erotic stimuli, or colloquially known as turn-ons. There are many potential stimuli, both physical
Stimulus (physiology)
In physiology, a stimulus is a detectable change in the internal or external environment. The ability of an organism or organ to respond to external stimuli is called sensitivity....
or mental
Stimulus (psychology)
In psychology, stimuli are energy patterns which are registered by the senses. In behaviorism and related stimulus–response theories, stimuli constitute the basis for behavior, whereas in perceptual psychology they constitute the basis for perception.In the second half of the 19th century, the...
, which can cause a person to become sexually aroused. Sexual arousal usually leads to physiological changes in the aroused person, some of which are pronounced while others are more subtle.
Sexual arousal may not lead to an actual sexual activity, beyond a mental arousal and the physiological changes that accompany it. Given sufficient stimulation
Sexual stimulation
Sexual stimulation is any stimulus that leads to, enhances and maintains sexual arousal, and may lead to ejaculation and/or orgasm...
, sexual arousal in humans will typically end in an orgasm
Orgasm
Orgasm is the peak of the plateau phase of the sexual response cycle, characterized by an intense sensation of pleasure...
; but arousal may 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 zoneErogenous zone
An erogenous zone is an area of the human body that has heightened sensitivity, the stimulation of which may result in the production of erotic sensations or sexual excitement.People have erogenous zones all over their bodies, but which areas are more sensitive than others vary...
or acts of foreplay
Foreplay
In human sexual behavior, foreplay is a set of intimate psychological and physically intimate acts between two or more people meant to create desire for sexual activity and sexual arousal. Either or any of the sexual partners may initiate the foreplay, and they may not be the active partner during...
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 (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
Kiss
A kiss is the act of pressing one's lips against the lips or other body parts of another person or of an object. Cultural connotations of kissing vary widely. Depending on the culture and context, a kiss can express sentiments of love, passion, affection, respect, greeting, friendship, and good...
ing, cuddling
Hug
A hug is a form of physical intimacy, that usually involves closing or holding the arms around the neck, back, or waist of another person; if more than two persons are involved, this is referred to as a group hug. A hug, sometimes in association with a kiss, eye contact or other gestures, is a...
, and petting of an erogenous zone
Erogenous zone
An erogenous zone is an area of the human body that has heightened sensitivity, the stimulation of which may result in the production of erotic sensations or sexual excitement.People have erogenous zones all over their bodies, but which areas are more sensitive than others vary...
. This may in turn make the person desire direct sexual stimulation
Sexual stimulation
Sexual stimulation is any stimulus that leads to, enhances and maintains sexual arousal, and may lead to ejaculation and/or orgasm...
of those parts of their body which would normally be out of bounds, such as breast
Breast
The breast is the upper ventral region of the torso of a primate, in left and right sides, which in a female contains the mammary gland that secretes milk used to feed infants.Both men and women develop breasts from the same embryological tissues...
s, nipple
Nipple
In its most general form, a nipple is a structure from which a fluid emanates. More specifically, it is the projection on the breasts or udder of a mammal by which breast milk is delivered to a mother's young. In this sense, it is often called a teat, especially when referring to non-humans, and...
s, buttocks
Buttocks
The buttocks are two rounded portions of the anatomy, located on the posterior of the pelvic region of apes and humans, and many other bipeds or quadrupeds, and comprise a layer of fat superimposed on the gluteus maximus and gluteus medius muscles. Physiologically, the buttocks enable weight to...
and/or genitals
Sex organ
A sex organ, or primary sexual characteristic, as narrowly defined, is any of the anatomical parts of the body which are involved in sexual reproduction and constitute the reproductive system in a complex organism; flowers are the reproductive organs of flowering plants, cones are the reproductive...
, and to sexual activity.
The erotic stimuli may originate from a source unrelated to the object of subsequent sexual interest. For example, many people may find nudity
Nudity
Nudity is the state of wearing no clothing. The wearing of clothing is exclusively a human characteristic. The amount of clothing worn depends on functional considerations and social considerations...
, erotica
Erotica
Erotica are works of art, including literature, photography, film, sculpture and painting, that deal substantively with erotically stimulating or sexually arousing descriptions...
or pornography
Pornography
Pornography or porn is the explicit portrayal of sexual subject matter for the purposes of sexual arousal and erotic satisfaction.Pornography may use any of a variety of media, ranging from books, magazines, postcards, photos, sculpture, drawing, painting, animation, sound recording, film, video,...
sexually arousing, which may generate a general sexual interest which is satisfied with sexual activity. When sexual arousal is achieved by or dependent on the use of objects, it is referred to as sexual fetishism
Sexual fetishism
Sexual fetishism, or erotic fetishism, is the sexual arousal a person receives from a physical object, or from a specific situation. The object or situation of interest is called the fetish, the person a fetishist who has a fetish for that object/situation. Sexual fetishism may be regarded, e.g...
, or in some instances a paraphilia
Paraphilia
Paraphilia is a biomedical term used to describe sexual arousal to objects, situations, or individuals that are not part of normative stimulation and that may cause distress or serious problems for the paraphiliac or persons associated with him or her...
.
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
McGill University Health Centre
The McGill University Health Centre is a network of teaching and community hospitals in Montreal, Quebec, Canada affiliated with McGill University....
in Montreal
Montreal
Montreal is a city in Canada. It is the largest city in the province of Quebec, the second-largest city in Canada and the seventh largest in North America...
, Canada
Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...
used the method of thermal
Thermal
A thermal column is a column of rising air in the lower altitudes of the Earth's atmosphere. Thermals are created by the uneven heating of the Earth's surface from solar radiation, and are an example of convection. The sun warms the ground, which in turn warms the air directly above it...
imaging to record baseline temperature
Temperature
Temperature is a physical property of matter that quantitatively expresses the common notions of hot and cold. Objects of low temperature are cold, while various degrees of higher temperatures are referred to as warm or hot...
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 very individualistic and varies from one time to the next depending on many circumstances.
Unlike many other animals, human
Human
Humans are the only living species in the Homo genus...
s do not have a mating season, and both sexes are potentially capable of sexual arousal throughout the year.
Sexual arousal 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 his or her 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
Sexual arousal disorder
Sexual arousal disorder is characterized by a lack or absence of sexual fantasies and desire for sexual activity in a situation that would normally produce sexual arousal, or the inability to attain or maintain typical responses to sexual arousal. The disorder is found in the DSM-IV...
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
Recreational drug use
Recreational drug use is the use of a drug, usually psychoactive, with the intention of creating or enhancing recreational experience. Such use is controversial, however, often being considered to be also drug abuse, and it is often illegal...
, 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, and 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, 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, which is a spontaneous, persistent, and uncontrollable arousal, and the physiological changes associated with arousal. Another problem which some people have in controlling their level of arousal is referred to as sexual addiction
Sexual addiction
Sexual addiction is a popular model to explain hypersexuality—sexual urges, behaviors, or thoughts that appear extreme in frequency or feel out of one's control...
.
Physiological changes
Sexual arousal causes different physical changes, most significantly in the sex organSex organ
A sex organ, or primary sexual characteristic, as narrowly defined, is any of the anatomical parts of the body which are involved in sexual reproduction and constitute the reproductive system in a complex organism; flowers are the reproductive organs of flowering plants, cones are the reproductive...
s (genital organs). Sexual arousal for a man is usually indicated by the swelling
Tumescence
Tumescence is the quality or state of being tumescent or swollen. Tumescence usually refers to the normal engorgement with blood of the erectile tissues, marking sexual excitation and possible readiness for sexual activity...
and erection
Erection
Penile erection is a physiological phenomenon where the penis becomes enlarged and firm. Penile erection is the result of a complex interaction of psychological, neural, vascular and endocrine factors, and is usually, though not exclusively, associated with sexual arousal...
of the penis
Penis
The penis is a biological feature of male animals including both vertebrates and invertebrates...
when blood fills the corpus cavernosum
Corpus cavernosum penis
The corpus cavernosum penis is one of a pair of sponge-like regions of erectile tissue which contain most of the blood in the penis during penile erection...
. 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
Clitoris
The clitoris is a sexual organ that is present only in female mammals. In humans, the visible button-like portion is located near the anterior junction of the labia minora, above the opening of the urethra and vagina. Unlike the penis, which is homologous to the clitoris, the clitoris does not...
and vulva
Vulva
The vulva consists of the external genital organs of the female mammal. This article deals with the vulva of the human being, although the structures are similar for other mammals....
, as well as vaginal transudation - the seeping of moisture through the vaginal walls which serves as lubrication
Vaginal lubrication
Vaginal lubrication is a lubricating fluid that is naturally produced in a woman's vagina. Vaginal lubrication or moistness is present at all times, but production increases significantly during a woman's sexual arousal in anticipation of sexual intercourse...
.
In females: |
In males: |
|---|---|
 Female sexual arousal. In the left image female genitalia are in normal state. In the right image the female is sexually aroused, the vulva is wet and the labia are slightly engorged.
|
Male sexual arousal. On the left of the image the male genitalia are in regular, flaccid state; on the right the male is sexually aroused and his penis has become erect. Erection Penile erection is a physiological phenomenon where the penis becomes enlarged and firm. Penile erection is the result of a complex interaction of psychological, neural, vascular and endocrine factors, and is usually, though not exclusively, associated with sexual arousal... Dorsal veins of the penis Dorsal veins of the penis can refer to:* superficial dorsal vein of the penis* deep dorsal vein of the penis... may become more prominent Foreskin In male human anatomy, the foreskin is a generally retractable double-layered fold of skin and mucous membrane that covers the glans penis and protects the urinary meatus when the penis is not erect... often exposing the glans penis Glans penis The glans penis is the sensitive bulbous structure at the distal end of the penis. The glans penis is anatomically homologous to the clitoral glans of the female... Pre-ejaculate Pre-ejaculate is the clear, colorless, viscous fluid that emits from the urethra of a man's penis when he is sexually aroused. It is similar in composition to semen, but has some significant chemical differences... Scrotum In some male mammals the scrotum is a dual-chambered protuberance of skin and muscle containing the testicles and divided by a septum. It is an extension of the perineum, and is located between the penis and anus. In humans and some other mammals, the base of the scrotum becomes covered with curly... Pupillary response Pupillary response or dilation of the pupil is a physiological response that varies the size of the pupil of the eye via the iris dilator muscle... |
Female physiological changes
The beginnings of sexual arousal in a womanWoman
A woman , pl: women is a female human. The term woman is usually reserved for an adult, with the term girl being the usual term for a female child or adolescent...
's body is usually marked by vaginal lubrication
Vaginal lubrication
Vaginal lubrication is a lubricating fluid that is naturally produced in a woman's vagina. Vaginal lubrication or moistness is present at all times, but production increases significantly during a woman's sexual arousal in anticipation of sexual intercourse...
(wetness), swelling and engorgement
Engorgement
In biology, engorgement is a naturally occurring or pathological condition of vessels being saturated with fluids. It may happen for instance in the breast or in other erectile tissues like the penis....
of the external genitals
Vulva
The vulva consists of the external genital organs of the female mammal. This article deals with the vulva of the human being, although the structures are similar for other mammals....
, and internal enlargement of the vagina
Vagina
The vagina is a fibromuscular tubular tract leading from the uterus to the exterior of the body in female placental mammals and marsupials, or to the cloaca in female birds, monotremes, and some reptiles. Female insects and other invertebrates also have a vagina, which is the terminal part of the...
. 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
Clitoris
The clitoris is a sexual organ that is present only in female mammals. In humans, the visible button-like portion is located near the anterior junction of the labia minora, above the opening of the urethra and vagina. Unlike the penis, which is homologous to the clitoris, the clitoris does not...
and the labia, along with increased redness or darkening of the skin in these areas. Further changes to the internal organs also occur including to the internal shape of the vagina and to the position of the uterus
Uterus
The uterus or womb is a major female hormone-responsive reproductive sex organ of most mammals including humans. One end, the cervix, opens into the vagina, while the other is connected to one or both fallopian tubes, depending on the species...
within the pelvis. Other changes include an increase in heart rate
Heart rate
Heart rate is the number of heartbeats per unit of time, typically expressed as beats per minute . Heart rate can vary as the body's need to absorb oxygen and excrete carbon dioxide changes, such as during exercise or sleep....
as well as in blood pressure
Blood pressure
Blood pressure is the pressure exerted by circulating blood upon the walls of blood vessels, and is one of the principal vital signs. When used without further specification, "blood pressure" usually refers to the arterial pressure of the systemic circulation. During each heartbeat, BP varies...
, 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
Orgasm is the peak of the plateau phase of the sexual response cycle, characterized by an intense sensation of pleasure...
. After orgasm, some women do not want any further stimulation and the sexual arousal quickly dissipates. Instructions have been published for keeping the sexual excitement going 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 physiological 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, sexual arousal, beliefs about and attitudes to sex, pain, and the ability to reach orgasm in women in their 40s and after menopause
Menopause
Menopause is a term used to describe the permanent cessation of the primary functions of the human ovaries: the ripening and release of ova and the release of hormones that cause both the creation of the uterine lining and the subsequent shedding of the uterine lining...
. 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
Estrogens , oestrogens , or œstrogens, are a group of compounds named for their importance in the estrous cycle of humans and other animals. They are the primary female sex hormones. Natural estrogens are steroid hormones, while some synthetic ones are non-steroidal...
levels may be associated with increased vaginal dryness and less clitoral erection
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 exclusively, associated with sexual...
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.
Male physiological changes
It is normal to correlate the erectionErection
Penile erection is a physiological phenomenon where the penis becomes enlarged and firm. Penile erection is the result of a complex interaction of psychological, neural, vascular and endocrine factors, and is usually, though not exclusively, associated with sexual arousal...
of the penis
Penis
The penis is a biological feature of male animals including both vertebrates and invertebrates...
with male
Male
Male refers to the biological sex of an organism, or part of an organism, which produces small mobile gametes, called spermatozoa. Each spermatozoon can fuse with a larger female gamete or ovum, in the process of fertilization...
sexual arousal. Physical or psychological stimulation, or both, leads to vasodilation
Vasodilation
Vasodilation refers to the widening of blood vessels resulting from relaxation of smooth muscle cells within the vessel walls, particularly in the large arteries, smaller arterioles and large veins. The process is essentially the opposite of vasoconstriction, or the narrowing of blood vessels. When...
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
Corpus spongiosum
Corpus spongiosum is the mass of spongy tissue surrounding the male urethra within the penis...
). The penis grows enlarged and firm, the skin of the scrotum
Scrotum
In some male mammals the scrotum is a dual-chambered protuberance of skin and muscle containing the testicles and divided by a septum. It is an extension of the perineum, and is located between the penis and anus. In humans and some other mammals, the base of the scrotum becomes covered with curly...
is pulled tighter, and the testes are pulled up against the body. However the relationship between erection and arousal is not one-to-one. 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
Nocturnal penile tumescence is the spontaneous occurrence of an erection of the penis during sleep. All men without physiological erectile dysfunction experience this phenomenon, usually three to five times during the night...
) 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 sexual drive - 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
Glans penis
The glans penis is the sensitive bulbous structure at the distal end of the penis. The glans penis is anatomically homologous to the clitoral glans of the female...
or head of the erect penis will swell wider and, as the genitals become further engorged with blood, their colour 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
Perineum
In human anatomy, the perineum is a region of the body including the perineal body and surrounding structures...
. With further sexual stimulation, the 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 sometimes, in some men.
As sexual stimulation continues, the muscles of the pelvic floor
Pelvic floor
The pelvic floor or pelvic diaphragm is composed of muscle fibers of the levator ani, the coccygeus, and associated connective tissue which span the area underneath the pelvis. The pelvic diaphragm is a muscular partition formed by the levatores ani and coccygei, with which may be included the...
, the ductus deferens (between the testicles and the prostate), the seminal vesicle
Seminal vesicle
The seminal vesicles or vesicular glands are a pair of simple tubular glands posteroinferior to the urinary bladder of male mammals...
s and the prostate gland itself may begin to contract in a way that forces sperm and semen into the urethra
Urethra
In anatomy, the urethra is a tube that connects the urinary bladder to the genitals for the removal of fluids out of the body. In males, the urethra travels through the penis, and carries semen as well as urine...
inside the penis. This is the onset of orgasm and it is likely, once this has started, that the man will continue to ejaculate 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
Vasocongestion 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, sexual arousal, REM sleep, strong emotions, and illnesses and allergic reactions.-Illnesses:Menstrual...
, will subside in a short time. Repeated or prolonged stimulation without orgasm and ejaculation can lead to discomfort in the testes that is sometimes called 'blue balls
Blue balls
Blue balls is a slang term for the condition of temporary fluid congestion in the testicles and prostate region, accompanied by acute testicular pain, caused by prolonged and unsatisfied sexual arousal in the human male. The term is thought to have originated in the United States, first appearing...
'.
After orgasm and ejaculation, men, like women, usually experience a refractory period
Refractory period
In physiology, a refractory period is a period of time during which an organ or cell is incapable of repeating a particular action, or the amount of time it takes for an excitable membrane to be ready for a second stimulus once it returns to its resting state following an excitation...
characterised by loss of erection, a subsidence in any sex flush, less interest in sex, and a feeling of relaxation that can be attributed to the neurohormone
Neurohormone
A neurohormone is any hormone produced and released by neurons.Examples include:*Thyrotropin-releasing hormone *Gonadotropin-releasing hormone *Adrenocorticotropin-releasing hormone*Oxytocin*Antidiuretic hormone *Epinephrine...
s oxytocin
Oxytocin
Oxytocin is a mammalian hormone that acts primarily as a neuromodulator in the brain.Oxytocin is best known for its roles in sexual reproduction, in particular during and after childbirth...
and prolactin
Prolactin
Prolactin also known as luteotropic hormone is a protein that in humans is encoded by the PRL gene.Prolactin is a peptide hormone discovered by Henry Friesen...
. The intensity and duration of the refractory period can be very short in a highly aroused young man in what he sees as a highly arousing situation, perhaps without even a noticeable loss of erection. It can be as long as a few hours or days in mid-life and older men.
Human sexual response cycle
During the late 1950s and early 1960s, William H. Masters and Virginia E. JohnsonMasters and Johnson
The Masters and Johnson research team, composed of William H. Masters and Virginia E. Johnson, pioneered research into the nature of human sexual response and the diagnosis and treatment of sexual disorders and dysfunctions from 1957 until the 1990s....
conducted many important studies into human sexuality
Human sexuality
Human sexuality is the awareness of gender differences, and the capacity to have erotic experiences and responses. Human sexuality can also be described as the way someone is sexually attracted to another person whether it is to opposite sexes , to the same sex , to either sexes , or not being...
. In 1966, they released Human Sexual Response
Human sexual response cycle
The human sexual response cycle is a four-stage model of physiological responses during sexual stimulation. These phases, in order of their occurrence, are the excitement phase, plateau phase, orgasmic phase, and resolution phase. The term was coined by William H. Masters and Virginia E...
, detailing four stages of physiological changes in humans during sexual stimulation: excitement, plateau, orgasm
Orgasm
Orgasm is the peak of the plateau phase of the sexual response cycle, characterized by an intense sensation of pleasure...
, and resolution.
Singer's model of sexual arousal
Singer presents a model of the process of sexual arousal, 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 notes 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.Sexual arousal in 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. DolphinDolphin
Dolphins are marine mammals that are closely related to whales and porpoises. There are almost forty species of dolphin in 17 genera. They vary in size from and , up to and . They are found worldwide, mostly in the shallower seas of the continental shelves, and are carnivores, mostly eating...
s and bonobo
Bonobo
The bonobo , Pan paniscus, previously called the pygmy chimpanzee and less often, the dwarf or gracile chimpanzee, is a great ape and one of the two species making up the genus Pan. The other species in genus Pan is Pan troglodytes, or the common chimpanzee...
s, for example, are both well known to use sex as a "social tool to strengthen and maintain bonds." Ethologists have long documented the exchanges of sex to promote group cohesion in social animals. Cementing social bondage is one of the most prominent theorized selective advantages of group selection
Group selection
In evolutionary biology, group selection refers to the idea that alleles can become fixed or spread in a population because of the benefits they bestow on groups, regardless of the alleles' effect on the fitness of individuals within that group....
theory. Experts in the evolution of sex
Evolution of sex
The evolution of sexual reproduction is currently described by several competing scientific hypotheses. All sexually reproducing organisms derive from a common ancestor which was a single celled eukaryotic species. Many protists reproduce sexually, as do the multicellular plants, animals, and fungi...
such as John Maynard Smith
John Maynard Smith
John Maynard Smith,His surname was Maynard Smith, not Smith, nor was it hyphenated. F.R.S. was a British theoretical evolutionary biologist and geneticist. Originally an aeronautical engineer during the Second World War, he took a second degree in genetics under the well-known biologist J.B.S....
advocate for the idea that the exchange of sexual favors helps congeal and localize the assortment of alleles in isolated population and therefore is potentially a very strong force in evolution
Evolution
Evolution is any change across successive generations in the heritable characteristics of biological populations. Evolutionary processes give rise to diversity at every level of biological organisation, including species, individual organisms and molecules such as DNA and proteins.Life on Earth...
. Maynard Smith also has 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 Equilibrium 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 EffectBaldwin effect
The Baldwin effect, also known as Baldwinian evolution or ontogenic evolution, is a theory of a possible evolutionary processes that was originally put forward in 1896 in a paper, "A New Factor in Evolution," by American psychologist James Mark Baldwin. The paper proposed a mechanism for specific...
. The end result of these sorts of things can be very novel structures such as the Pseudo-penis
Pseudo-penis
A pseudo-penis is a term used of any structure found on an animal that while superficially appearing to be a penis, is derived from a different developmental path.-Mammals:...
of the female spotted hyena
Spotted Hyena
The spotted hyena also known as laughing hyena, is a carnivorous mammal of the family Hyaenidae, of which it is the largest extant member. Though the species' prehistoric range included Eurasia extending from Atlantic Europe to China, it now only occurs in all of Africa south of the Sahara save...
. The display of secondary sex characteristics in humans such as a penis-like enlarged clitoris
Clitoris
The clitoris is a sexual organ that is present only in female mammals. In humans, the visible button-like portion is located near the anterior junction of the labia minora, above the opening of the urethra and vagina. Unlike the penis, which is homologous to the clitoris, the clitoris does not...
in females during arousal and gynecomastia
Gynecomastia
Gynecomastia or Gynaecomastia, , is the abnormal development of large mammary glands in males resulting in breast enlargement. The term comes from the Greek γυνή gyné meaning "woman" and μαστός mastós meaning "breast"...
in males are thought to have once been objects of mate selection 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
Cross-cultural studies, sometimes called Holocultural Studies, is a specialization in anthropology and sister sciences that uses field data from many societies to examine the scope of human behavior and test hypotheses about human behavior and culture. Cross-cultural studies is the third form of...
. A dramatic example of this is the high rates of secondary sex characteristic
Secondary sex characteristic
Secondary sex characteristics are features that distinguish the two sexes of a species, but that are not directly part of the reproductive system. They are believed to be the product of sexual selection for traits which give an individual an advantage over its rivals in courtship and aggressive...
dimorphism
Sexual dimorphism
Sexual dimorphism is a phenotypic difference between males and females of the same species. Examples of such differences include differences in morphology, ornamentation, and behavior.-Examples:-Ornamentation / coloration:...
in some Southeast Asia human populations.