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Sexual arousal (also sexual excitement) describes the
physiological Physiology (; ) is the scientific Science () is a systematic enterprise that builds and organizes knowledge Knowledge is a familiarity or awareness, of someone or something, such as facts A fact is an occurrence in the real world. ...
and psychological responses in preparation for
sexual intercourse Sexual intercourse (or coitus or copulation) is a sexual activity Human sexual activity, human sexual practice or human sexual behaviour is the manner in which humans experience and express their sexuality Human sexuality is the w ...

sexual intercourse
or when exposed to sexual stimuli. A number of physiological responses occur in the body and mind as preparation for sexual intercourse, and continue during the acion. Male arousal will lead to an
erection An erection (clinically: penile erection or penile tumescence) is a physiological phenomenon in which the penis A penis (plural ''penises'' or ''penes'' () is the primary sexual organ that male animals use to inseminate females (or h ...

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 The breast is one of two prominences located on the upper ventral region of the torso of primates. In females, it serves as the mammary gland, which produces and secret ...
,
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 In human anatomy The human body is the structure of a human being. It is com ...

vulva
,
clitoris The clitoris ( or ) is a female sex organ present in mammals, ostriches and a limited number of #Other animals, other animals. In humans, the visible portion – the glans – is at the front junction of the labia minora (inner lips), ...
, vaginal walls, and
vaginal lubrication Vaginal lubrication is a naturally produced fluid that a . Vaginal lubrication is always present, but production increases significantly near and during in anticipation of . Vaginal dryness is the condition in which this lubrication is insuff ...

vaginal lubrication
.
Mental stimuli Mental may refer to: * of or relating to the mind Films * Mental (2012 film), ''Mental'' (2012 film), an Australian comedy-drama * Mental (2016 film), ''Mental'' (2016 film), a Bangladeshi romantic-action movie * ''Mental'', a 2008 documentary by ...
and physical stimuli such as touch, and the internal fluctuation of
hormones A hormone (from the Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is approximately 10.7 m ...
, 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#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is approxima ...

orgasm
. It may also be pursued for its own sake, even in the absence of an orgasm.


Terminology

There are several informalities, terms and phrases to describe sexual arousal, including ''horny'', ''turned on'', ''randy'', ''steamy'', and ''lustful''. Things that precipitate human sexual arousal are called erotic stimuli and colloquially known as turn-ons.


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#REDIRECT Erogenous zone An erogenous zone (from Greek , ''érōs'' "love"; and English ''-genous'' "producing", from Greek , ''-genḗs'' "born") is an area of the human body The human body is the structure of a human being. It is composed of ...
or acts of
foreplay Foreplay is a set of emotionally and physically intimate acts between two or more people meant to create sexual arousal Sexual arousal (also sexual excitement) is typically the arousal Arousal is the physiological and psychological ...
can result in arousal, especially if it is accompanied with the anticipation of imminent sexual activity. Sexual arousal may be assisted by a
romantic Romantic may refer to: Genres and eras * The Romantic era, an artistic, literary, musical and intellectual movement of the 18th and 19th centuries ** Romantic music, of that era ** Romantic poetry, of that era ** Romanticism in science, of that er ...
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 The somatosensory system is a part of the sensory nervous system The sensory nervous system is a part of the nervous system In biology, the classical doctrine of the nervous system determines that it is a Complex system, highly comple ...
(touch), visual, and
olfactory The sense of smell, or olfaction, is the special sense In medicine Medicine is the Art (skill), art, science, and Praxis (process) , practice of caring for a patient and managing the diagnosis, prognosis, Preventive medicine, prevention, the ...
(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 Love encompasses a range of str ...

kiss
ing,
cuddling A hug is a form of Affection, endearment, universal in Communities, human communities, in which two or more people put their arms around the neck, back, or waist of one another and hold each other closely. If more than two people are involved, it ...
, and
petting
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 Standard anatomical terms of location deal unambiguously with the of s, including s. Terms used generally derive from or roots and used to describe something in its . Th ...

breast
s,
nipple The nipple is a raised region of tissue on the surface of the breast The breast is one of two prominences located on the upper region of the of s. In females, it serves as the , which produces and secretes milk to feed s. Both females ...

nipple
s,
buttocks The buttocks (singular: buttock) are two rounded portions of the exterior anatomy of most mammals Mammals (from Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European l ...

buttocks
and/or
genitals A sex organ (or reproductive organ) is any part of an animal or plant that is involved in sexual reproduction Sexual reproduction is a type of reproduction Reproduction (or procreation or breeding) is the biological process Biological ...
, 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 Human sexuality is the way people experience and express themselves sexually. This involves bio ...
. Erotic stimuli may originate from a source unrelated to the object of subsequent sexual interest. For example, many people may find
nudity Nudity is the state of being in which a human Humans (''Homo sapiens'') are the most populous and widespread species of primates, characterized by bipedality, opposable thumbs, hairlessness, and intelligence allowing the use of culture, ...

nudity
,
erotica Erotica is (in a broad sense) any literary or artistic work that deals substantively with subject matter that is , or but (in a strict sense) is not generally considered to be . may use any artistic form to depict erotic content, including , ...
or
pornography Pornography (often shortened to porn) is the portrayal of Human sexual activity, sexual subject matter for the exclusive purpose of sexual arousal.
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 Sexual fetishism or erotic fetishism is a sexual fixation on a nonliving object or nongenital body part. The object of interest is called the fetish; the person who has ''a fetish'' for that object is a fetishist. A sexual fetish may be regarded ...
, or in some instances a
paraphilia Paraphilia (previously known as sexual perversion and sexual deviation) is the experience of intense sexual arousal Sexual arousal (also sexual excitement) is typically the arousal Arousal is the physiological and psychological ...
. 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 Montreal ( ; officially Montréal, ) is the List of the largest municipalities i ...
in
Montreal Montreal ( ; officially Montréal, ) is the second-most populous city in Canada Canada is a country in the northern part of . Its extend from the to the and northward into the , covering , making it the world's . Its southern and w ...

Montreal
(in Canada) used the method of
thermal imaging Infrared thermography (IRT), thermal video and/or thermal imaging, is a process where a thermal camera A thermographic camera (also called an infrared camera or thermal imaging camera or thermal imager) is a device that creates an image using ...
to record baseline
temperature Temperature ( ) is a physical quantity that expresses hot and cold. It is the manifestation of thermal energy Thermal radiation in visible light can be seen on this hot metalwork. Thermal energy refers to several distinct physical concept ...

temperature
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 other animals,
human Humans (''Homo sapiens'') are the most abundant and widespread species In biology, a species is the basic unit of biological classification, classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A speci ...

human
s do not have a
mating season Seasonal breeders are animal Animals (also called Metazoa) are multicellular eukaryotic organisms that form the Kingdom (biology), biological kingdom Animalia. With few exceptions, animals Heterotroph, consume organic material, Cellular res ...
, 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 his or her partner's erotic stimuli and turn-offs. Some people feel embarrassed by sexual arousal and some are
sexually inhibited A sexual inhibition is a conscious or subconscious constraint or curtailment by a person of behavior relating to specific human sexual behavior, sexual matters or practices, a discussion of sexual matters or viewing certain sexual material. To some ...
. 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 Hypoactive sexual desire disorder (HSDD), hyposexuality or inhibited sexual desire (ISD) is considered a sexual dysfunction and is characterized as a lack or absence of sexual fantasies and desire for sexual activity, as judged by a clinician. Fo ...
. There are many reasons why a person fails to be aroused, including a mental disorder, such as
depression Depression may refer to: Mental health * Depression (mood), a state of low mood and aversion to activity * Mood disorders characterized by depression are commonly referred to as simply ''depression'', including: ** Dysthymia ** Major depressive ...
, 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 currently controversial whether it should be included as a clinical diagnosis used by mental healthcare professionals. Nymphomania and Satyriasis were terms previously us ...
, 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 Sexual stimulation is any stimulus (i ...
, 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 An erection (clinically: penile erection or penile tumescence) is a physiological phenomenon in which the penis A penis (plural ''penises'' or ''penes'' () is the primary sexual organ that male animals use to inseminate females (or h ...

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 (zoology), copulation. Such organs occur in many animals, both #Vertebrates, vertebrate ...

penis
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 The clitoris ( or ) is a female sex organ present in mammals, ostriches and a limited number of #Other animals, other animals. In humans, the visible portion – the glans – is at the front junction of the labia minora (inner lips), ...

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 In human anatomy The human body is the structure of a human being. It is com ...

vulva
, as well as vaginal transudation - the seeping of moisture through the vaginal walls which serves as
lubrication Lubrication is the process or technique of using a lubricant A lubricant is a substance that helps to reduce friction Friction is the force In physics Physics is the natural science that studies matter, its Elementary particl ...

lubrication
.


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 a . Vaginal lubrication is always present, but production increases significantly near and during in anticipation of . Vaginal dryness is the condition in which this lubrication is insuff ...

vaginal lubrication
(wetness; though this can occur without arousal due to infection or cervical mucus production around ovulation), swelling and engorgement of the , and internal lengthening and enlargement of the
vagina In mammal Mammals (from Latin language, Latin , 'breast') are a group of vertebrate animals constituting the class (biology), class Mammalia (), and characterized by the presence of mammary glands which in Female#Mammalian female, femal ...

vagina
. 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 The clitoris ( or ) is a female sex organ present in mammals, ostriches and a limited number of #Other animals, other animals. In humans, the visible portion – the glans – is at the front junction of the labia minora (inner lips), ...

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 fold ...

labia
, 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 main female hormone-responsive, sex organ, secondary sex organ of the reproductive system in humans and most other mammals. Things occurring in the uterus are described with t ...

uterus
within the
pelvis The pelvis (plural pelves or pelvises) is the lower part of the trunk, between the abdomen The abdomen (colloquially called the belly, tummy, midriff or stomach) is the part of the body between the thorax (chest) and pelvis, in humans and in ...
. Other changes include an increase in
heart rate Heart rate is the speed of the heartbeat Heartbeat or heartbeats may refer to: Physiology *Cardiac cycle, of the heart *Contraction of the cardiac muscle, muscles of the heart, or a perceived effect of it, such as: **Heart sounds, the noises gene ...

heart rate
as well as in
blood pressure Blood pressure (BP) is the pressure Pressure (symbol: ''p'' or ''P'') is the force In physics, a force is an influence that can change the motion (physics), motion of an Physical object, object. A force can cause an object with mas ...

blood pressure
, feeling hot and flushed and perhaps experiencing tremors. A
sex flush Flushing is to become markedly red in the face and often other areas of the skin, from various physiology, physiological conditions. Flushing is generally distinguished, despite a close physiological relation between them, from blushing, which is m ...
may extend over the chest and upper body. If sexual stimulation continues, then sexual arousal may peak into
orgasm Orgasm (from Greek#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is approxima ...

orgasm
. 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, 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 48 and 52. 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 Estrogens or oestrogens, are a class of natural or synthetic sex hormone Sex hormones, also known as sex steroids, gonadocorticoids and gonadal steroids, are steroid hormone A steroid hormone is a steroid that acts as a hormone. Steroid ho ...

estrogen
levels may be associated with increased vaginal dryness and less
clitoral erection Clitoral erection is a physiological phenomenon where the clitoris The clitoris ( or ) is a female sex organ present in mammals, ostriches and a limited number of #Other animals, other animals. In humans, the visible portion – the glan ...
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

It is normal to correlate the
erection An erection (clinically: penile erection or penile tumescence) is a physiological phenomenon in which the penis A penis (plural ''penises'' or ''penes'' () is the primary sexual organ that male animals use to inseminate females (or h ...

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 (zoology), copulation. Such organs occur in many animals, both #Vertebrates, vertebrate ...

penis
with male sexual arousal. Physical or psychological stimulation, or both, leads to
vasodilation Vasodilation is the widening of blood vessel The blood vessels are the components of the circulatory system The circulatory system, also called the cardiovascular system or the vascular system, is an organ system An organ system is ...

vasodilation
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 Tissue may refer to: Biology * Tissue (biology), an ensemble of similar cells that together carry out a specific function * ''Triphosa haesitata'', a species of geometer moth found in North Ame ...
). The penis grows enlarged and firm, the skin of the
scrotum The scrotum or scrotal sac is an Anatomy, 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 scr ...

scrotum
is pulled tighter, and the
testes Testicle or testis (plural testes) is the male Male (symbol: ♂) is the sex of an organism that produces the gamete (sex cell) known as sperm, which fuses with the larger female gamete, or ovum, in the process of fertilization. A male or ...

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 is a spontaneous 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 ...
) 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 Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome, known as Latium. Thro ...

glans
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), includin ...
. 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 Flushing is to become markedly red in the face and often other areas of the skin, from various physiology, physiological conditions. Flushing is generally distinguished, despite a close physiological relation between them, from blushing, which is m ...
in some men. As sexual stimulation continues,
orgasm Orgasm (from Greek#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is approxima ...

orgasm
begins, when the muscles of the
pelvic floor The pelvic floor or pelvic diaphragm is composed of muscle fibers of the levator ani The levator ani is a broad, thin muscle Muscle is a soft tissue found in most animals. Muscle cells contain protein Proteins are large biomolecules ...
, the
vas deferens The vas deferens, or ductus deferens, is part of the male reproductive system The male reproductive system consists of a number of sex organ A sex organ (or reproductive organ) is any part of an animal or plant that is involved in sexual r ...

vas deferens
(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 The urinary bladder, or simply bladder, is a hollow muscular MUSCULAR (DS-200B), located i ...
s and the
prostate The prostate is both an accessory gland of the male reproductive system The male reproductive system consists of a number of sex organ A sex organ (or reproductive organ) is any part of an animal or plant that is involved in sexual repr ...

prostate
gland itself may begin to contract in a way that forces sperm and semen into the
urethra The urethra (from Greek#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is appro ...

urethra
inside the penis. Once this has started, it is likely that the man will continue to
ejaculate Ejaculation is the discharge of semen Semen, also known as seminal fluid, is an organic fluid created to contain spermatozoon, spermatozoa. It is secreted by the gonads (sexual glands) and other sexual organs of male or hermaphrodite, her ...
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 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 Sexual arousal (also sexua ...
, 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 (also known as lover's nuts) is slang Slang is language (words, phrases, and usages) of an informal register. It also sometimes refer to the language generally exclusive to the members of particular In-group and out-group, in-g ...
"). 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
neurohormoneA neurohormone is any hormone A hormone (from the Greek participle , "setting in motion") is any member of a class of signaling molecules in multicellular organisms, that are transported to distant organs to regulate physiology and / or behavior ...
s
oxytocin Oxytocin (Oxt or OT) is a peptide hormonePeptide hormones or protein hormones are hormones whose molecules are peptides or proteins, respectively. The latter have longer amino acid chain lengths than the former. These hormones have an effect o ...

oxytocin
and
prolactin Prolactin, also known as lactotropin, is a protein Proteins are large biomolecule , showing alpha helices, represented by ribbons. This poten was the first to have its suckture solved by X-ray crystallography by Max Perutz and Sir Jo ...
. 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.


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.


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 cente ...
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 The concept of interpersonal relationship involves social associations, connections, or affiliations between two or more people. Interpersonal relationships vary in their degree ...
prompts them to engage with sexual stimuli, which leads to an experience of
sexual desire Sexual desire is a Motivation, motivational state and an interest in sexual objects or activities, or as a wish, or drive to seek out sexual objects or to engage in Human sexual activity, sexual activities. Synonyms for sexual desire are ''libido'', ...
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 system, male reproductive tissues such as testes and prostate, as well as promoting secondar ...
in women who were not using
hormonal contraception Hormonal contraception refers to birth control Birth control, also known as contraception, anticonception, and fertility control, is a method or device used to prevent pregnancy Pregnancy, also known as gestation, is the time during w ...
. In terms of brain activation, researchers have suggested that
amygdala The amygdala (; plural: amygdalae or amygdalas; also '; Latin from Greek language, Greek, , ', 'almond', 'tonsil') is one of two almond-shaped clusters of nucleus (neuroanatomy), nuclei located deep and lateral and medial, medially within the ...

amygdala
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.


Male

The relationship between
sexual desire Sexual desire is a Motivation, motivational state and an interest in sexual objects or activities, or as a wish, or drive to seek out sexual objects or to engage in Human sexual activity, sexual activities. Synonyms for sexual desire are ''libido'', ...
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 is the speed of the heartbeat Heartbeat or heartbeats may refer to: Physiology *Cardiac cycle, of the heart *Contraction of the cardiac muscle, muscles of the heart, or a perceived effect of it, such as: **Heart sounds, the noises gene ...

heart rate
,
blood pressure Blood pressure (BP) is the pressure Pressure (symbol: ''p'' or ''P'') is the force In physics, a force is an influence that can change the motion (physics), motion of an Physical object, object. A force can cause an object with mas ...

blood pressure
, and
erection An erection (clinically: penile erection or penile tumescence) is a physiological phenomenon in which the penis A penis (plural ''penises'' or ''penes'' () is the primary sexual organ that male animals use to inseminate females (or h ...

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 cente ...
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 language, Greek, , ', 'almond', 'tonsil') is one of two almond-shaped clusters of nucleus (neuroanatomy), nuclei located deep and lateral and medial, medially within the ...

amygdala
and
hypothalamic The hypothalamus (from Ancient Greek Ancient Greek includes the forms of the Greek language used in ancient Greece and the classical antiquity, ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following p ...

hypothalamic
responses than women. This suggests the amygdala plays a critical role in the processing of sexually arousing visual stimuli in men.


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 Biology is the natural science Natural science is a branch of science Science (from the Latin word ''scientia'', meaning ...
. 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. In psychoanalytic theory libido is psychic drive or energy, particularly associated with sexual instinct, but also present in other instinctive ...

sex drive
, 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 The concept of interpersonal relationship involves social associations, connections, or affiliations between two or more people. Interpersonal relationships vary in their degree ...
, 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 a Motivation, motivational state and an interest in sexual objects or activities, or as a wish, or drive to seek out sexual objects or to engage in Human sexual activity, sexual activities. Synonyms for sexual desire are ''libido'', ...
. 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 Female sexual arousal disorder (FSAD) is a disorder characterized by a persistent or recurrent inability to attain sexual arousal Sexual arousal (also sexual excitement) is typically the arousal Arousal is the physiological and psychol ...
; 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 ; 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 Cognition () refers to "the mental action or process of acquiring knowledge and understanding through thought, experience, and the senses". It encompasses many aspects of intellectual function Intellectual functioning refers to the "general men ...

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'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 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. As yet, 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 Masturbation ( ) is the sexual stimulation Sexual stimulation is any stimulus (including bodily contact) that leads to, enhances and maintains sexual arousal, and may lead to orgasm Orgasm (from Ancient Greek, Greek ὀργασμός ' ...

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, unfortunately limiting the generalizability of the dual control model. To date, one study comparing heterosexual and homosexual males found that
homosexual men Gay men are male homosexuals. Some bisexual men, bisexual and homoromantic men may also dually identify as gay, and a number of young gay men today also identify as queer. Historically, gay men have been referred to by a number of different ter ...
had similar scores for SIS2, but scored significantly higher for SIS1 and SES. Straight, lesbian, and bisexual women's scores on the SESII-W found that bisexual women scored higher on SES than the other groups and straight 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 The urinary bladder, or simply bladder, is a hollow muscular MUSCULAR (DS-200B), located i ...
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 In public relations Public relations (PR) is the practice of managing and disseminating information from an individual or an organization ...

University of California, Berkeley
) 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 university, private research university with its main campus in Potsdam (village), New York, Potsdam, New York, and additional graduate program and research facilities in the Capital District, New York, New York ...
) describes this model as follows: The "psychohydraulic model of sexuality" has been formulated most definitely in
psychoanalysis Psychoanalysis (from Greek language, Greek: + ) is a set of Theory, theories and Therapy, 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 bo ...

psychoanalysis
: 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 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 Sexual arousal (also sexua ...
of the
genital A sex organ (or reproductive organ) is any part of an animal or plant that is involved in sexual reproduction Sexual reproduction is a type of reproduction that involves a complex Biological life cycle, life cycle in which a gamete (such as a sp ...
tissues, including internal and external areas (e.g., ,
clitoris The clitoris ( or ) is a female sex organ present in mammals, ostriches and a limited number of #Other animals, other animals. In humans, the visible portion – the glans – is at the front junction of the labia minora (inner lips), ...

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 fold ...

labia
). There are a variety of methods used to assess genital sexual arousal in women.
Vaginal photoplethysmography Vaginal photoplethysmography (VPG, VPP) is a photoplethysmogram, technique using light to measure the vasocongestion, amount of blood in the walls of the vagina. The device that is used is called a vaginal photometer. Use The device is used to try ...
(VPG) can measure changes in vaginal blood volume or phasic changes in vasocongestion associated with each heartbeat. Clitoral photoplethysmography 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 A thermographic camera (also called an infrared camera or thermal imaging camera or thermal imager) is a device that creates an image using ...
provides a direct measure of genital sexual arousal by measuring changes in
temperature Temperature ( ) is a physical quantity that expresses hot and cold. It is the manifestation of thermal energy Thermal radiation in visible light can be seen on this hot metalwork. Thermal energy refers to several distinct physical concept ...

temperature
associated with increased blood flow to the external genital tissues. Similarly, labial thermistor clips 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 Imaging is the representation or reproduction of an object's form; especially a visual representation (i.e., the formation of an image). Imaging technology is the application of materials and methods to ...
(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 . 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 phallometry (the objective measurement of sexual arousal in males), research studies in pedophilia, and for the "courtship di ...
. 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 (zoology), copulation. Such organs occur in many animals, both #Vertebrates, vertebrate ...

penis
, 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 A thermographic camera (also called an infrared camera or thermal imaging camera or thermal imager) is a device that creates an image using ...
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 Romantic may refer to: Genres and eras * The Romantic era, an artistic, literary, musical and intellectual movement of the 18th and 19th centuries ** Romantic music, of that era ** Romantic poetry, of that era ** ...
men experience much higher genital and subjective arousal to women than to men. This pattern is reversed for
homosexual Homosexuality is romantic Romantic may refer to: Genres and eras * The Romantic era, an artistic, literary, musical and intellectual movement of the 18th and 19th centuries ** Romantic music, of that era ** Romantic poetry, of that era ** R ...
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 a . Vaginal lubrication is always present, but production increases significantly near and during in anticipation of . Vaginal dryness is the condition in which this lubrication is insuff ...

vaginal lubrication
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 understo ...

non-consensual
. 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.


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''. Research has shown a
reliable Reliability, reliable, or unreliable may refer to: Science, technology, and mathematics Computing * Data reliability (disambiguation), Data reliability, a property of some disk arrays in computer storage * High availability * Reliability (computer ...
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: *InternalityAn internality is the long-term benefit or cost to an individual that they do not consider when making the decision to consume a good or service. One way this is related to behavioral economics is by means of the c ...
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 A thermographic camera (also called an infrared camera or thermal imaging camera or thermal imager) is a device that creates an image using ...
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#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is appr ...

hormone
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 system, male reproductive tissues such as testes and prostate, as well as promoting secondar ...
,
cortisol Cortisol is a steroid hormone, in the glucocorticoid class of hormones. When used as a medication, it is known as hydrocortisone. It is produced in many animals, mainly by the ''zona fasciculata'' of the adrenal cortex in the adrenal gland. ...

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 cycle, estrous and menstrual cycle, menstrual female reproductive cycles. Estradiol is resp ...

estradiol
. 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 Hormonal contraception refers to birth control Birth control, also known as contraception, anticonception, and fertility control, is a method or device used to prevent pregnancy Pregnancy, also known as gestation, is the time during w ...
. Also, women who participate in
polyandrous Polyandry (; from grc-gre, πολυ- ''poly-'', "many" and ἀνήρ ''anēr'', "man") is a form of polygamy Polygamy (from Greek language, Late Greek , ''polygamía'', "state of marriage to many spouses") is the practice of marriage, ma ...
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 Dolphin is the common name of aquatic mammal Aquatic and semiaquatic mammals are a diverse group of mammal Mammals (from Latin language, Latin , 'breast') are a group of vertebrate animals constituting the class (biology), class Mam ...

Dolphin
s and
bonobo The bonobo (; ''Pan paniscus''), also historically called the pygmy chimpanzee and less often, the dwarf or gracile chimpanzee, is an Endangered Species, endangered great ape and one of the two species making up the genus ''Pan (genus), Pan''; th ...

bonobo
s, for example, are both well known to use sex as a "social tool to strengthen and maintain bonds."
Ethologists Ethology is the scientific Science () is a systematic enterprise that Scientific method, builds and organizes knowledge in the form of Testability, testable explanations and predictions about the universe."... modern science is ...
have long documented the exchanges of sex to promote group cohesion in
social animals Sociality is the degree to which individuals in an animal Animals (also called Metazoa) are multicellular eukaryotic organisms that form the Kingdom (biology), biological kingdom Animalia. With few exceptions, animals Heterotroph, consum ...
. 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 more conventional level of the individual. Early authors such as V. C. Wynne-Edwards and Konrad Lorenz argued that ...
theory. Experts in the evolution of sex such as
John Maynard Smith John Maynard Smith (6 January 1920 – 19 April 2004) was a British theoretical and mathematical evolutionary biologist Evolutionary biology is the subfield of biology that studies the evolutionary processes ( natural selection, commo ...

John Maynard Smith
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 one of two, or more, forms of a given gene In biology, a gene (from ''genos'' "...Wilhelm Johannsen coined the word gene to describe the Mendelian_inheritance ...

alleles
in isolated population and therefore is potentially a very strong force in
evolution Evolution is change in the heritable Heredity, also called inheritance or biological inheritance, is the passing on of Phenotypic trait, traits from parents to their offspring; either through asexual reproduction or sexual reproduction, ...

evolution
. 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 frequency, allele and genotype frequencies in a population will remain constant from generation ...
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 Evolutionary biology is the subfield of biology that studies the evolution, evolutionary processes (natural selection, common descent, speciation) that produced the Biodiversity, diversity of life on Earth. In the 193 ...
. The display of
secondary sex characteristic Secondary sex characteristics are features that appear during puberty Puberty is the process of physical changes through which a child Biologically, a child (plural children) is a human Humans (''Homo sapiens'') are the most ab ...
s in humans such as a penis-like enlarged
clitoris The clitoris ( or ) is a female sex organ present in mammals, ostriches and a limited number of #Other animals, other animals. In humans, the visible portion – the glans – is at the front junction of the labia minora (inner lips), ...

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 The breast is one of two prominences located on the upper ventral Standard anatomica ...

gynecomastia
in males are thought to have once been objects of
mate selection Mate choice is one of the primary mechanisms under which evolution Evolution is change in the Heredity, heritable Phenotypic trait, characteristics of biological populations over successive generations. These characteristics are the Gene expr ...
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 Anthropology is the scientific study of human Humans (''Homo sapiens'') are the most abundant and widespread s ...
. 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-penisA 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 The spotted hyena (''Crocuta crocuta''), also known as the laughing hyena, is a hyena Hyenas, or hyaenas (from Ancient Greek , ), are feliformia, feliform carnivoran mammals of the family Hyaenidae . With only four extant species (each in t ...

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. Therefore, they can be classified by their che ...
*
Erectile tissue Erectile tissue is tissue in the body with numerous vascular spaces, or cavernous tissue Cavernous tissue refers to blood-filled spaces lined by endothelium and surrounded by smooth muscle. It is present in the erectile tissue of the penis and clit ...
*
Kinsey Reports The 1948 first edition of ''Sexual Behavior in the Human Male'', the first of the two Kinsey Reports The Kinsey Reports are two scholarly books on human sexual behavior Human sexual activity, human sexual practice or human sexual behaviour i ...
* Nudity and sexuality *
Priapism Priapism is a condition in which a penis A penis (plural ''penises'' or ''penes'' () is the primary that animals use to females (or s) during . Such organs occur in many animals, both and , but males do not bear a penis in every animal ...
*
Sexology Sexology is the scientific study of human sexuality, including human sexual interests, Human sexual activity, behaviors, and functions. The term ''sexology'' does not generally refer to the non-scientific study of sexuality, such as social criti ...
*
Sexual frustration Sexual frustration is a sense of dissatisfaction stemming from a discrepancy between a person's desired and achieved sexual activity Human sexual activity, human sexual practice or human sexual behaviour is the manner in which humans experie ...


References


External links

* {{DEFAULTSORT:Sexual Arousal