User:8kb12/sandbox

Sexual Arousal

"Turn-on" redirects here. For other uses, see Turn On (disambiguation).

Martin van Maele's print Francion 15 depicts a couple engaging in foreplay outdoors

Sexual arousal (also sexual excitement) is the arousal 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 mental stimuli and physical stimuli such as hormones which can cause a person to become sexually aroused.

Sexual arousal may not lead to any actual sexual activity, beyond a mental arousal and the physiological changes that accompany it. Given sufficient stimulation, sexual arousal in humans will typically end in an orgasm; but arousal may be pursued for its own sake, even in the absence of an orgasm. It is thought that women may get more aroused at a certain time during their menstrual cycle, either before, after or during their period, however, there are studies that do not support this theory .

When men are aroused they typically get an erection. When women are aroused, they typically get vaginal lubrication (wetness).

Terminology

There are several informalities, terms and phrases to describe sexual arousal including horny, turned on, randy, steamy, and lustful.

Erotic stimuli

Main article: Erogenous zone

Kissing and touching can cause sexual arousal

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 or acts of foreplay 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 kissing, cuddling, and petting of an erogenous zone. This may in turn make the person desire direct sexual stimulation of those parts of their body which would normally be out of bounds, such as breasts, nipples, buttocks and/or genitals, 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, erotica or pornography 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, or in some instances a paraphilia.

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 in Montreal, Canada used the method of thermal imaging to record baseline 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 very individualistic and varies from one time to the next depending on many circumstances.

Unlike many other animals, humans do not have a mating season, and both sexes are potentially capable of sexual arousal throughout the year.

Sexual arousal disorders

See also: Sexual arousal disorder, Hypoactive sexual desire disorder, and Female sexual arousal disorder

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 or hypoactive sexual desire disorder. There are many reasons why a person fails to be aroused, including a mental disorder, such as depression, drug use, or a medical or physical condition. The lack of sexual arousal may be due to a general lack of sexual desire or due to a lack of sexual desire for the current partner. A person may always have had no or low sexual desire or the lack of desire may have been acquired during the person's life. There are also complex philosophical and psychological issues surrounding sexuality. Attitudes towards life, death, childbirth, one's parents, friends, family, contemporary society, the human race in general, and particularly one's place in the world play a substantive role in determining how a person will respond in any given sexual situation.

On the other hand, a person may be hypersexual, 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.

Physiological changes

Sexual arousal causes different physical changes, most significantly in the sex organs (genital organs). Sexual arousal for a man is usually indicated by the swelling and erection of the 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 and vulva, as well as vaginal transudation - the seeping of moisture through the vaginal walls which serves as lubrication.

In females:

In males:

File:Female sexual arousal.JPG 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. Erection of nipples Vaginal lubrication Vasocongestion of the vaginal walls Tumescence and erection of the clitoris and labia Elevation of the cervix and uterus, and expansion of the back of the vagina Change in shape, color and size of the labia majora and labia minora Pupil dilation

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. Penile tumescence and erection The veins in the penis may become more prominent Tightening and/or retraction of the foreskin often exposing the glans penis Emission of pre-ejaculatory fluid Swelling of the testes Ascension of the testes Tensing and thickening of the scrotum Pupil dilation

Female physiological changes

The beginnings of sexual arousal in a woman's body is usually marked by vaginal lubrication (wetness), swelling and engorgement of the external genitals, and internal enlargement of the 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 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 within the pelvis. Other changes include an increase in heart rate as well as in blood pressure, feeling hot and flushed and perhaps experiencing tremors. A sex flush may extend over the chest and upper body.

If sexual stimulation continues, then sexual arousal may peak into orgasm. 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. 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 levels may be associated with increased vaginal dryness and less clitoral erection 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 erection of the penis with male sexual arousal. Physical or psychological stimulation, or both, leads to 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 penis grows enlarged and firm, the skin of the scrotum 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) 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 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. 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, the ductus deferens (between the testicles and the prostate), the seminal vesicles and the prostate gland itself may begin to contract in a way that forces sperm and semen into the urethra 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, 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'.

After orgasm and ejaculation, men usually experience a refractory period 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 neurohormones oxytocin and prolactin. 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.

Psychological changes

See also: Libido

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 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 prompts them to engage with sexual stimuli, which leads to an experience of sexual desire 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 in women who were not using hormonal contraceptives. In terms of brain activation, researchers have suggested that amygdala responses are not solely determines 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 and arousal in men is complex, with a wide range of factors increasing or decreasing sexual arousal. Physiological responses, such as heart rate, blood pressure, and erection, are often discordant with self-reported subjective perceptions of arousal. This inconsistency suggests that psychological, or cognitive aspects, also have a strong effect on sexual arousal. The cognitive aspects of sexual arousal in men are not completely known, but it 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 expectations, and sexual attitudes, contribute to sex differences observed in subjective sexual arousal. Specifically, while watching visual stimuli, men are more influenced by the sex of an actor portrayed in the stimulus, and men typically prefer a stimulus that allows objectification of the actor and projection of themselves into the scenario. For more information on cognitions and sexual arousal visit the Psychological Association: The science of sexual arousal. There are reported differences in brain activation to sexual stimuli, with men showing higher levels of amygdala and 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

Main article: Human sexual response cycle

During the late 1950s and early 1960s, William H. Masters and Virginia E. Johnson conducted many important studies into human sexuality. In 1966, they released 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

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.

Basson’s sexual response cycle

Basson presents 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, 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, which leads her to seek out and be receptive to sexual stimuli; women then feel sexual arousal, in addition to sexual desire. The cycle results in an enhanced feeling of intimacy. Basson emphasizes the idea that a lack of spontaneous desire should not be taken as an indication of female sexual dysfunction; many women experience sexual arousal and responsive desire simultaneously when they are engaged in sexual activity.

Toates’ incentive-motivation model

Toates presents a model of sexual motivation, arousal, and behaviour that combines the principles of incentive-motivation theory and hierarchical control of behaviour. The basic incentive-motivation model of sex suggests that incentive cues in the environment invade the nervous system, which results in sexual motivation. Positive sexual experiences enhance motivation, while negative experiences reduce it. Motivation and behaviour are organized hierarchically; each are controlled by a combination direct (external stimuli) and indirect (internal cognitions) factors. Excitation and inhibition of behaviour 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 behaviour can be active or conscious (e.g., choosing not to have sex) or it can be passive or unconscious (e.g., being unable to have sex due to fear). Toates emphasizes the importance considering cognitive representations in addition to external stimuli; he suggests that mental representations of incentives are interchangeable with excitatory external stimuli for eliciting sexual arousal and motivation.

Assessment of genital arousal

See also: Psychophysiology

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.

Female

See also: Vaginal photoplethysmograph, Clitoral photoplethysmograph, Thermography (sexual psychophysiology), Labial Thermistor, and Laser Doppler Imaging

Sexual arousal in women is characterized by vasocongestion of the genital tissues, including internal and external areas (e.g., vaginal walls, clitoris, and labia). There are a variety of methods used to assess genital sexual arousal in women. Vaginal photoplethysmography (VPG) can measure changes in vaginal blood volume or phasic changes in vasocongestion associated with each heartbeat. Clitoral photoplethysmography functions in a similar way to VPG, but measures changes in clitoral blood volume, rather than vaginal vasocongestion. Thermography provides a direct measure of genital sexual arousal by measuring changes in 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 (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.

Male

See also: Penile plethysmography and Thermology

One of the responses involved with sexual behaviour in males is penile erection; therefore, the volume (or circumference) change during penile erection is a convenient measure of sexual arousal, which was first developed by Kurt Freund . This measurement of blood flow to the male genitals is known as penile plethysmography. This is commonly measured using a strain gauge, which is comprised of a simple, mercury strain gauge encompassed in a ring of rubber. The ring surrounds the penis, but does not constrict or cause discomfort . The measure is found to be a reliable and valid measurement of male arousal . More recently, thermography 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-specify is a sexual-arousal pattern that is more commonly found amongst men than women. 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-specify look at genital responses, or physiological changes, as well as subjective responses, or what people report their arousal levels to be. Heterosexual men experience much higher genital and subjective arousal to women than to men. This pattern in reversed for homosexual men. Studies have found that women have a non-specific genital response pattern of sexual arousal, meaning their genital responses are only modestly related to their preferred category. Women subjective responses are category-specific, because they typically report their highest level of arousal to their preferred stimulus, however, the reported difference in levels of arousal is typically much smaller than men’s.

Concordance

Sexual arousal results from 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 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 versus external genital engorgement subjectively, measured by vaginal photoplethysmography (VPG) and thermography, 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 and sexual arousal

Several hormones affect sexual arousal, including testosterone, cortisol, and estradiol, however, the specific roles of these hormones are not clear. Testosterone is the most commonly studied hormone involved with sexuality. Testosterone 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 with females. Research has found testosterone levels increase as a result of sexual cognitions in females that do not use hormonal contraception. Also, women who participate in polyandrous 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 increases testosterone as an effect. 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.

Two birds who appear to be exhibiting affection

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. Dolphins and bonobos, 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 theory. Experts in the evolution of sex such as John Maynard Smith 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. 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 Effect. The end result of these sorts of things can be very novel structures such as the Pseudo-penis of the female spotted hyena. The display of secondary sex characteristics in humans such as a penis-like enlarged clitoris in females during arousal and gynecomastia 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. A dramatic example of this is the high rates of secondary sex characteristic dimorphism in some Southeast Asia human populations.

See also

• Aphrodisiac
• Erotica
• Erogenous zone
• Hypersexuality
• Human sexuality
• Impotence
• Kinsey report
• Libido
• Nudity and sexuality
• Orgasm
• Orgasm control
• Persistent sexual arousal syndrome
• Post-SSRI sexual dysfunction
• Priapism
• Sex
• Sexology
• Sexual attraction
• Sexual desire
• Sexual frustration
• Sexual intercourse
• Sexual orientation

Vaginal Photoplethysmograph

"vaginal photoplethysmography" redirects here. For other uses, see vaginal photoplethysmography (disambiguation).

Vaginal photoplethysmography (VPG) refers to measurement of vaginal vasocongestion. A vaginal photoplethysmograph is a clear acrylic, menstrual tampon-shaped device that contains a light source, and a light detector. The light source illuminates the capillary bed of the vaginal wall and the blood circulating within it. As the amount of blood in the vaginal tissue increases, more light is reflected into the photosensitive cell of the device. VPG is the most common way to assess vaginal blood flow and is widely used to measure genital sexual arousal in women.

VPG was designed to be easily inserted by research participants; however, some participants perceive insertion of the VPG to be invasive. Past research suggests that studies using VPG result in small and unrepresentative samples. However, more recent assessments of women’s willingness to participate in sexual psychophysiological research using VPG found no evidence of sampling bias influencing results.

Development

VPG was first introduced in 1967 by Palti and Berovici, who affixed a light source and photosensitive cell onto a gynecological speculum and recorded vaginal pulse waves. Sintchak and Geer improved on the device in 1975 by using a vaginal probe. The vaginal photoplethysmograph was the first practical and reliable device for the measurement of vaginal blood flow.

Signal

The output of the VPG can be filtered into two types of signals, which have different properties. The direct current signal, is a measure of vaginal blood volume (VBV) and reflects the total blood volume in the vaginal tissues. The alternating current signal is a measure vaginal pulse amplitude (VPA) and reflects the pressure change within the blood vessels of the vaginal wall associated with each heartbeat . While changes in VBV occur in response to sexual and anxiety-inducing stimuli, changes in VPA only occur in response to sexual stimuli. Since VPA is a more sensitive and specific measure of sexual arousal, many researchers use it instead of VBV.

VPA is defined as the peak-to-trough amplitude of the vaginal pulse wave. It is calculated by subtracting the means of all troughs from the means of all peaks experienced during stimulus presentation.VPA lacks an absolute scale of measurement; each unit of change (mV) does not correspond directly with a physiological change (cf. penile plethysmography). Since VPA does not have a standard unit of measurement it is difficult for researchers to make between-participant comparisons.

 

Clitoral Photoplethysmograph

"Clitoral photoplethysmograph" redirects here. For other uses, see Clitoral photoplethysmograph (disambiguation).

Clitoral photoplethysmography uses a direct current signal to measure clitoral blood volume (CBV). A clitoral photoplethysmograph is a small clear acrylic device that contains a light source, and a light detector. The light source illuminates the capillary bed of the clitoral tissue and the blood circulating within it. As clitoral engorgement increases, more light is reflected into the photosensitive cell of the device. The clitoral photoplethysmograph is placed by the participant between the labia minora; the light detector is oriented toward the clitoris. It can be attached to a vaginal photoplethysmograph so that both CBV and VPA can be measured simultaneously. Gerritsen found clitoral photoplethysmography to be a valid and sensitive tool for measuring female genital response. In contrast to the vaginal photoplethysmography, clitoral photoplethysmographs are sensitive to the inhibition of sexual response. The authors suggest that clitoral photoplethysmography is particularly informative for examining sexual inhibition.

 

Thermography (sexual psychophysiology)

See also: Thermography and Thermography (medical)

Thermography measures infrared radiation emitted by matter. Thermographic cameras detect this radiation and provide a continuous temperature reading of objects. Researchers began to use thermographic cameras to measure sexual arousal in the 1980s; however these measurements were discontinuous and were confined to one pre-determined area of the body.

Recent research suggests that thermal imaging is a valid measure of sexual arousal in women. Thermography differentiates between responses to sexual stimuli and responses to control conditions, such that sexual stimuli elicit an increase in genital temperature but control stimuli do not. Thermography also has discriminant validity because increase in temperature in response to sexual stimuli is localized to the genitals; thigh temperature does not vary according to exposure to sexual versus nonsexual stimuli.

Using thermography has advantages over vaginal photoplethysmography (VPG) because it does not require genital manipulation or contact, it can be used in men and women, and it has an absolute scale that can be used to compare sexual response between-participants. A limitation of using thermography is that this method is costly compared to other methods, such as VPG. Also, some participants have reported feeling uncomfortable with having a thermographic camera pointed toward their genitals while they are viewing sexual stimuli.

 

Labial Thermistor Clip

The labial thermistor clip is used to measure changes in skin temperature of the labia minora associated blood engorgement of the labial tissue. This device consists of a thermistor affixed to a small metal clip that can be attached to the labia minora. The labial thermistor clip is the second most commonly used physiological measure of female genital response, next to the vaginal photoplethysmograph (VPG). Both devices can be used simultaneously.

The labial thermistor clip has some advantages over VPG, including better test-retest reliability, greater level of concordance between genital and self-reported sexual arousal, and an absolute unit of change (temperature). Like VPA, the labial thermistor clip has discriminant validity; that is, it detects differences between sexual and nonsexual stimuli. It is also sensitive to different levels of sexual arousal. The labial thermistor clip has some disadvantages because participants have difficulty with placing the device correctly and some report discomfort with using the device.

 

Laser Doppler Imaging (sexual psychophysiology)

Laser Doppler Imaging (LDI) is used to measure superficial blood flow in the skin. A laser Doppler perfusion imager functions by projecting an infrared laser beam over the skin. When light interacts with moving blood cells a small portion of it is shifted, detected, and converted into an electrical signal. LDI provides a direct measure of female sexual response that does not require genital contact; signals are gathered at a depth of two to three millimetres below the skin’s surface.

Two studies have suggested that LDI is a valid measure of female sexual arousal. Waxman and Pukall showed that LDI has discriminant validity; that is, it can differentiate sexual response from neutral, positive, and negative mood induced states.

Compared to vaginal photoplethysmography (VPG), LDI is advantageous because it does not require genital manipulation or contact. Also, LDI provides a direct measure of vasocongestion and has an absolute unit of measurement, consisting of flux or units of blood flow. The disadvantages of LDI are that it cannot provide a continuous measure of sexual response and the laser Doppler perfusion imager is much more costly that other methods of genital sexual arousal assessment, such as VPG