The Masters and Johnson sexual response cycle is a four-phase model of human sexual physiology published in 1966 by William Masters and Virginia Johnson, based on direct laboratory observation of hundreds of volunteers. The phases they identified are excitement, plateau, orgasm, and resolution, and the model became the most influential framework in sex research for decades. Modern neuroscience and broader clinical experience have confirmed many of its physiological observations while also exposing significant gaps, particularly in how it handles desire, individual variation, and sex differences.
The Four Phases and What Happens in Each
Masters and Johnson described sexual response as a predictable sequence that unfolds in roughly the same order every time. In the excitement phase, the body redirects blood flow toward the genitals. In men, this produces erection; in women, clitoral engorgement, swelling of the vaginal walls, and lubrication. These changes are driven by the parasympathetic nervous system relaxing smooth muscle in genital blood vessels, while rising heart rate and blood pressure supply the extra blood flow.1Psychiatry. The physiology of human sexual function – Section: Genital arousal Skin flushing, nipple erection, and muscle tension throughout the body also begin during this stage.
The plateau phase is essentially a sustained, intensified version of excitement. Masters and Johnson treated it as a distinct stage because they observed a period where physiological arousal holds at a high level before orgasm. Heart rate, blood pressure, and muscle tension continue climbing. In women, the outer third of the vagina swells with blood, forming what they called the “orgasmic platform.” In men, the testes elevate and increase in size. Not everyone experiences a clear plateau; for some people arousal builds continuously from excitement into orgasm without any identifiable holding pattern, which is one reason later researchers questioned whether this phase really deserves its own label.
Orgasm is the briefest phase, typically lasting seconds, and involves rhythmic involuntary contractions of the pelvic muscles alongside intense subjective pleasure. Research measuring these contractions in women found that anal and vaginal contractions are synchronized, with the interval between contractions gradually lengthening by about a tenth of a second as the series progresses.2PubMed. The female orgasm: pelvic contractions In men, orgasm is usually accompanied by ejaculation, though the two events are physiologically separable.
Resolution is the return to the unaroused baseline. Blood drains from the genitals, heart rate and breathing slow, and muscles relax. Masters and Johnson noted that men typically enter a refractory period during resolution, a window of time in which further orgasm is not possible. They observed that women do not necessarily experience this refractory period, which they took as evidence that women are capable of multiple orgasms in rapid succession.
What Brain Imaging Has Revealed
Masters and Johnson worked with electrodes, blood pressure cuffs, and direct visual observation. They had no way to see what the brain was doing. Functional MRI studies have since added a layer the original model could not capture. During orgasm in women, brain activity increases broadly across sensory, motor, reward, and frontal cortical regions, including the nucleus accumbens, insula, anterior cingulate cortex, hypothalamus, amygdala, hippocampus, and cerebellum.3PubMed Central. Brain Activity Unique to Orgasm in Women: An fMRI Analysis An earlier fMRI study identified a similar pattern, with activation in the hypothalamic paraventricular nucleus, basal ganglia, and brainstem structures including the central gray matter.4Annual Review of Sex Research. Functional MRI of the Brain during Orgasm in Women Activity ramps up gradually as arousal builds, peaks during orgasm, and then recedes, which broadly mirrors the arc Masters and Johnson described from a purely peripheral standpoint.
In men, PET and fMRI data show that penile stimulation increases activity in the somatosensory and motor cortices as well as the hippocampus and thalamus, with thalamic activation tracking closely with self-reported arousal levels.5Journal of Nuclear Medicine. Endogenous Opioid Release After Orgasm in Man: A Combined PET/Functional MRI Study These imaging studies paint a picture of orgasm as a whole-brain event rather than the localized genital reflex Masters and Johnson’s peripheral measurements implied. The reward circuitry involved overlaps heavily with what lights up during other intensely pleasurable experiences, which helps explain why orgasm feels qualitatively different from simple genital sensation.
The Neurochemistry Behind the Cycle
The original model was silent on brain chemistry. Researchers have since found that dopamine and serotonin systems play significant roles in regulating arousal and orgasm at the central level, alongside contributions from adrenergic, cholinergic, and neuropeptide pathways.6PubMed Central. Neuroanatomy and function of human sexual behavior: A neglected or unknown issue? This is clinically relevant because selective serotonin reuptake inhibitors (SSRIs), which raise serotonin levels, are notorious for suppressing orgasm and desire. Knowing the chemical architecture helps explain why those side effects happen and why adjusting the medication sometimes helps.
Measuring neurotransmitters in the living human brain is extremely difficult. One study that sampled cerebrospinal fluid during sexual arousal and orgasm found that norepinephrine rose steadily through arousal and orgasm and stayed elevated afterward, consistent with increasing sympathetic nervous system activity. However, the same study found no significant changes in dopamine or its metabolites in spinal fluid, despite dopamine’s known importance in animal models. The researchers suggested that dopamine release during sex may be too localized to specific brain regions to show up in lumbar fluid samples.7PubMed. Serial neurochemical measurement of cerebrospinal fluid during the human sexual response cycle Prolactin, meanwhile, surged in blood plasma after orgasm, a finding that shaped decades of theorizing about the refractory period.
The Refractory Period and the Prolactin Myth
For years, the post-orgasm prolactin surge was the leading candidate explanation for why men cannot immediately achieve another orgasm after ejaculation. The logic seemed tidy: prolactin rises, desire falls, erection becomes temporarily impossible. But animal research has substantially undercut this idea. A study in mice found that even when prolactin was artificially elevated to levels matching those seen after ejaculation, sexual behavior was completely unaffected. Conversely, blocking prolactin release during sex did not shorten the refractory period. In one mouse strain, suppressing prolactin actually made the refractory period longer, the opposite of what the theory predicted.8PubMed Central. No evidence for prolactin’s involvement in the post-ejaculatory refractory period
This matters because the prolactin explanation has been repeated confidently in textbooks and popular science writing for decades. If prolactin is not the driver, researchers still need to identify what actually creates the refractory period. The current thinking is that it likely involves multiple inhibitory mechanisms working together, possibly including serotonin release in specific brain regions, spinal cord inhibition, and peripheral fatigue of nerve pathways. The honest answer is that, as of now, nobody has pinpointed the mechanism with certainty.
Sex Differences in Resolution
Masters and Johnson’s observation that men and women differ in the resolution phase has held up under controlled laboratory testing. A study that tracked both subjective feelings and genital temperature after orgasm found that sexual arousal and desire dropped more quickly and consistently in men than in women. More men than women showed complete resolution of both subjective arousal and genital response, and men’s genital temperature decreased more, though it did not fully return to baseline within the measurement window.9PubMed. Gender similarities and differences in sexual arousal, desire, and orgasmic pleasure in the laboratory This is consistent with the idea that women’s capacity for multiple orgasms reflects a slower, less definitive physiological shutdown after climax.
But the same research also revealed that the differences between men and women were smaller in some domains than Masters and Johnson suggested. Subjective ratings of pleasure during orgasm, for instance, were similar. The model’s neat division, in which men follow a single-peak arc and women can follow a multi-peak one, is real but overstated as a universal sex difference. Individual variation within each sex is large enough that some men report minimal refractory periods and some women report rapid, complete resolution.
The Concordance Problem
One of the most interesting challenges to the Masters and Johnson framework involves what researchers call concordance: the degree to which genital arousal and subjective feelings of being turned on actually match. Masters and Johnson’s model implicitly assumed these two things track together, that physical signs of arousal indicate psychological arousal and vice versa. Research has shown this is often not the case, especially in women.
Studies measuring both genital blood flow and self-reported arousal find that the correlation between the two is moderate at best, and it varies based on attitudes and social context. Research examining how adherence to sexual double standards affects concordance found that subjective arousal explained only about a fifth to a third of the variance in genital response, even in people with relatively egalitarian attitudes.10International Journal of Clinical and Health Psychology. Study of Sexual Concordance in Men and Women with Different Typologies of Adherence to the Sexual Double Standard Your body can respond genitally to stimuli you do not find appealing, and you can feel desire without strong genital response. This disconnect means a model built entirely on measurable physiological changes, as Masters and Johnson’s was, inevitably misses a significant piece of the experience.
Where the Model Falls Short
The most commonly noted flaw in the original model is that it has no place for desire. Masters and Johnson started the cycle at excitement, the point where physical arousal is already underway. They treated wanting sex as self-evident rather than as a distinct psychological event worth modeling. In 1979, Helen Singer Kaplan added desire as a first phase, creating a three-stage model (desire, arousal, orgasm) that became the basis for the diagnostic categories of sexual dysfunction used in psychiatry for decades.
More fundamental criticism has focused on the model’s linear structure. Masters and Johnson described a one-way sequence, like climbing a mountain and coming down the other side. Critics have argued this reflects a male-typical pattern that does not capture many women’s experience, in which desire may not precede arousal but rather emerge from it. Rosemary Basson proposed a circular model in which many women begin from a position of sexual neutrality, become receptive to stimulation for reasons that may not involve spontaneous desire (intimacy, emotional connection, curiosity), and only experience desire once arousal is already underway.11PubMed. The female sexual response: a different model This responsive model of desire has been widely adopted in clinical practice because it describes a pattern that many women recognize as normal but that the original linear framework would have classified as disordered.
Broader critiques have targeted the research itself. The volunteers who agreed to have sex in a laboratory while being monitored were not a random sample of the population. The model has been criticized for imposing a false biological uniformity on sexuality by treating a single physiological sequence as universal, neglecting the diversity of human sexual experience and the role of context, meaning, and relationship dynamics.12PubMed Central. Historical, Scientific, Clinical and Feminist Criticisms of “The Human Sexual Response Cycle” Model The sample was overwhelmingly white, educated, and American, and the laboratory setting itself may have selected for people whose arousal patterns fit the linear model well.
The Dual Control Model
An alternative framework that has gained substantial research support since 2000 is the Dual Control Model, developed by Erick Janssen and John Bancroft at the Kinsey Institute. Rather than describing sexual response as a fixed sequence of phases, this model proposes that arousal depends on the balance between two independent systems: one that promotes sexual excitation and one that inhibits it.13PubMed. The dual control model: current status and future directions People vary in their propensity for both, and understanding that variation helps explain why the same stimulus can produce strong arousal in one person and nothing in another.
The model was originally developed to explain centrally mediated erectile difficulties in men, proposing that some erectile problems arise not from a failure of excitation but from excessive inhibition.14PubMed. The dual control model of male sexual response: a theoretical approach to centrally mediated erectile dysfunction It has since been extended to women and applied across a wide range of sexual behaviors. A scoping review of research using the model found it has been productive across diverse populations and sexual contexts.15PubMed. The Dual Control Model of Sexual Response: A Scoping Review, 2009-2022 Where Masters and Johnson asked “what are the stages of the body’s response?”, the Dual Control Model asks “why does the response happen or not happen in the first place?” The two frameworks are not mutually exclusive, but they answer fundamentally different questions.
Cross-cultural research using the Dual Control Model has also highlighted the role of attitudes and cultural context. A study comparing Chinese and Euro-Caucasian women in Canada found that sexual excitation scores were significantly lower in Chinese women, and that sexual attitudes partially explained the cross-cultural differences in arousal patterns.16Springer Link / PubMed Central. Dual Control Model in a Cross-Cultural Context: Role of Sexual Excitation in Sexual Response and Behavior Differences Between Chinese and Euro-Caucasian Women in Canada This kind of finding sits entirely outside the scope of the original Masters and Johnson model, which had no mechanism for cultural or attitudinal influences on the physiological response cycle.
How Aging Affects the Cycle
Masters and Johnson acknowledged that age changes sexual response, but their data came primarily from younger adults. Research on menopausal women and their partners has put numbers to the shift. In one study of couples where the woman was postmenopausal, about 36% of the women met criteria for sexual dysfunction, while about 17% of their male partners had erectile difficulties.17PubMed Central. The impact of menopause on sexual function in women and their spouses Every phase of the cycle can be affected by aging: excitement takes longer to develop, plateau may be harder to sustain, orgasm may become less intense or less reliable, and resolution may involve discomfort rather than simple relaxation.
In women, declining estrogen after menopause reduces vaginal lubrication and tissue elasticity, which directly slows the excitement phase and can make intercourse painful. In men, erections become less firm, take longer to achieve, and require more direct stimulation. These are not dysfunctions in themselves; they represent the normal physiological trajectory. The four-phase model is still recognizable in older adults, but the timing, intensity, and ease of each phase change enough that applying the young-adult template without adjustment leads to unnecessary anxiety about what is “normal.”
The Evolutionary Puzzle of Female Orgasm
One question the Masters and Johnson model raised but could not answer is why female orgasm exists at all. Male orgasm has an obvious reproductive function because it typically accompanies ejaculation. Female orgasm is not necessary for conception, which has made it an enduring puzzle in evolutionary biology. Two broad hypotheses compete. The byproduct hypothesis proposes that female orgasm is a developmental leftover, analogous to male nipples, existing because both sexes share early embryological development and orgasm is adaptive in men. The mate-choice hypothesis proposes that female orgasm evolved as a signal or filtering mechanism that favors certain partner traits.
A review of evidence for both hypotheses found more support for the mate-choice explanation, suggesting that female orgasm may increase the probability of fertilization from males whose genetic qualities would benefit offspring.18PubMed. Why women have orgasms: an evolutionary analysis A more recent analysis partially supported this, finding that female orgasm was positively associated with partner attributes related to both genetic quality and the capacity for emotional connection and resource investment, consistent with both sire-choice and pair-bond versions of the mate-choice theory.19PubMed. Evolutionary Role of the Female Orgasm: Insights into Mate Choice and Beyond Neither study claims to have settled the question. The debate continues in part because testing evolutionary hypotheses about human sexuality is inherently difficult, and both explanations could contain elements of truth.
The Autonomic Nervous System Is Not as Simple as the Model Implied
Masters and Johnson’s physiological observations led to a simplified picture of arousal: the parasympathetic nervous system drives excitement (relax, dilate blood vessels, increase flow), and the sympathetic system drives orgasm (contract, release, climax). The actual picture is messier. Research into the autonomic basis of arousal has proposed that both sympathetic and parasympathetic branches are active during arousal, and that the balance between them may be modulated by gonadal hormones, with androgens and estrogens influencing each branch differently.20PubMed. The physiological basis of human sexual arousal: neuroendocrine sexual asymmetry This dual activation matters clinically. Drugs that broadly suppress sympathetic activity (like some blood pressure medications) can impair orgasm, while drugs that suppress parasympathetic activity (like anticholinergics) can impair the excitement phase. Knowing which branch is doing what helps predict which medications will cause which sexual side effects.
The interplay between branches also helps explain why anxiety, which spikes sympathetic activity, can either enhance or derail arousal depending on the context. A little sympathetic activation may boost arousal if the person is already in an excitatory psychological state, while too much tips the balance toward inhibition. The Masters and Johnson model, with its clean parasympathetic-then-sympathetic handoff, could not account for this paradox, but the more nuanced understanding of dual autonomic activation can.