Understanding Desire and Pleasure Thanks to the Human Sexual Response Cycle

The human sexual response cycle can’t be summed up by a simple biological reflex. It is, in fact, complex coordination of the brain, hormones, nervous system and each individual's past both personally and in relationships. Understanding the sexual response cycle means understanding how the body and the mind work together to manage desire, arousal and pleasure.

The human sexual response cycle refers to all physiological and psychological changes that take place during arousal, the plateau phase, orgasm and finally the return to calm. It engages neural networks, hormonal systems, vascular and muscular mechanisms, as well as emotional, cognitive and contextual factors. It constitutes both a subjective experience and a universal physiological experience. Our scientific understanding of sexual response is the fruit of decades of research, influencing not only our definition and understanding of sexuality, but also how we deal with sexual dysfunctions (Masters & Johnson, 1966 ; Kaplan, 1979 ; Basson, 2001).

In the US in the 1950s, sexuality was still a taboo subject, even in academic circles. Until this point, it’s only been studied through interviews (specifically those of Alfred Kinsey), observing animals and via psychoanalytical speculations. William Masters, an obstetrician-gynaecologist, offered up something new: directly observing human physiological reactions during sexual activity.

A rigorous and methodical clinician, in 1957 he was granted authorisation to carry out a discreet research programme, on the physiology of human sexuality. He took an assistant, Virginia Johnson, who possessed decisive qualities: keen observation skills, social intelligence and the ability to put participants at ease in a sensitive situation. They immediately formed the perfect duo.

Between 1957 and the mid-1960s, they recruited hundreds of volunteers, both men and women, who had accepted to participate in observational sessions in the lab. In total, Masters and Johnson analysed thousands of sexual response cycles using electrocardiograms, blood pressure and respiratory sensors, devices measuring genital vasocongestion, photographic and cinematographic instruments. They even had a transparent Plexiglas device they nicknamed ‘Ulysses,’ which allowed them to observe vaginal and uterine lubrication and contractions in real time.

Participants masturbated or had sexual relations in a controlled, secure environment, whilst the researchers recorded their physiological data. They discovered and described a relatively stereotyped physiological sequence, organised into four phases: arousal, plateau, orgasm, resolution (Masters & Johnson, 1966). At that time, their observations rocked the scientific community like an earthquake: men and women, despite their anatomical differences, go through the same overarching physiological phases.

One of the key findings highlighted the importance that the clitoris plays in the feminine sexual response cycle, and that all feminine orgasms imply rhythmical contractions of the outer third of the vagina (until this point, people believed vaginal and clitoral orgasms were completely distinct). They also highlight genital vasocongestion (blood flow) as a central mechanism of sexual response, generalised myotonia (muscle tension), the male refractory period, and the ability for some women to have multiple orgasms. Their approach transforms sexuality into an observable biological phenomenon rather than a moral or theoretical concept.

By proposing a four phase model, the founding work of Masters and Johnson marked a major turning point in the history of sexology. Since this study, other researchers have added to this vision, for example Helen Kaplan (Kaplan, 1979) and Rosemary Basson (Basson, 2001, 2002), by integrating the dimension of desire and the complexity of the lived feminine experience.

Here’s a non-exhaustive list of the four phases as observed by the researchers:

The excitement phase corresponds to the start of sexual activation. In women, we can observe vulval engorgement, vaginal lubrication through transudation and clitoral erection. In men, increased testicular volume, penile erection by filling the corpora cavernosa, and possible pre-ejaculatory secretion. In both sexes, heart rate quickens, blood pressure rises and muscles contract. This phase can be triggered by sensory (vision, odour, hearing, touch), cognitive or relational stimuli.

The plateau corresponds to the intensification of arousal. In women, vasocongestion increases and the clitoris partially retracts under its hood. In men, erection stabilises, the testicles reach their maximum volume and rise, and sperm is ready to be expelled. Cardiovascular parameters reach levels comparable to moderate to intense physical exertion. This phase prepares the body for orgasm.

Orgasm is a brief but intense phase. In men, it involves the emission and expulsion of semen, as well as contractions of the bulbospongiosus muscles. In women, it involves rhythmic contractions of the outer third of the vagina and, potentially, the uterus. In both sexes, the contractions occur at intervals of approximately 0.8 seconds, gradually decreasing in speed and intensity after orgasm (Masters & Johnson, 1966). The absence of orgasm does not necessarily mean the absence of pleasure or satisfaction.

For example, the female sexual response can follow several curves, depending on whether there is one, several or no orgasms:

Resolution corresponds to the return of the basal state. In men, this generally includes a refractory period, defined as the temporary incapability to obtain a new erection or orgasm despite adequate stimulation. Length varies considerably depending on age and health status. In women, the refractory period doesn’t work in a systematic manner. Some women can experience multiple orgasms without a significant drop in arousal, while others describe a phase of transient post-orgasmic sensitivity comparable to a refractory period (Levin, 2002 ; Levin, 2009).

Understanding the sexual response cycle has helped to relieve many patients of guilt, as their difficulties now have identifiable physiological causes. Nevertheless, the arousal-plateau-orgasm-resolution cycle does not always reflect the emotional richness of the sexual experience. This model has been supplemented by other contemporary models, which remind us that sexuality is more circular than linear.

In 1979, Helen Kaplan proposed a three-phase model: desire, arousal, orgasm. She insists upon the fact that desire is widely influenced by psychological factors (self-image, emotions, performance anxiety etc.) as well as relational factors (relationships, conflict, culture etc.), and not just by the hormonal system or physiological reflexes (Kaplan, 1979).

If we integrate the desire phase into those determined by Masters and Johnson, the average human sexual response curve looks like this:

Indeed, sexual response can be influenced by the context and the quality of the relationship, as desire often makes up part of the relational dynamic. Thus, emotional intimacy between partners can be as powerful a trigger as physical stimulation.

What’s more, desire and arousal are two distinct processes: we can feel desire without experiencing an immediate bodily response, and inversely, the body can react without the mind being fully engaged in desire. To sum things up, some people feel desire then arousal, others arousal and then desire. For example, in men, erection is generally an indicator of subjective arousal, but it can also be a reflex (particularly nocturnal erection during REM sleep). Similarly, in women, vaginal lubrication can occur in the absence of subjective feelings of arousal, indicating a possible discrepancy between physiological response and psychological experience (Levin, 2009).

In the early 2000s, Rosemary Basson offered a circular model for the feminine sexual response cycle (Basson, 2001, 2002). According to this model, desire isn’t always spontaneous in women. It can also emerge in response to stimulation in a positive relational context. According to Basson, sexual desire can, therefore, be reactionary. What’s more, sexual satisfaction doesn’t depend solely on orgasm, since the relational context also plays a determining role. This model has greatly influenced our understanding of desire and feminine sexual disorders.

Sexual response models have structured the classification of sexual dysfunction, such as problems with desire, arousal, erection or lubrication and orgasm. Understanding neurobiological mechanisms (Rowland, 2006 ; Meston & Frohlich, 2000) also helps us to distinguish between organic causes (neurological, endocrine, vascular etc.), psychological causes (anxiety, depression, trauma etc.) and relational (lack of experience, disagreements, unspoken words, co-dependency etc.) causes.

On a neuroendocrine level, orgasm is accompanied by the release of oxytocins, an increase in prolactin, and intense activation of reward circuits. Thus, dopaminergic circuits play a key role in sexual desire and motivation. The refractory period also involves dopaminergic and serotonergic changes (Levin, 2009; Seizert, 2018). Similarly, serotonin and prolactin can exert an inhibitory effect on certain phases of the sexual response (Seizert, 2018; Rowland, 2006).

In short, sex hormones that influence sexual response are:

• Testosterone: influences desire in both men and women (Meyer, 2016)
• Oestrogen: thickens the vaginal wall and increases lubrication
• Oxytocin: involved in orgasm and feelings of attachment
• Prolactin: associated with post-orgasmic sexual satiety (Meston & Frohlich, 2000), is produced most notably during breastfeeding

These systems interact in permanence with psychological and relational dimensions, which is why you might sometimes here sexologists say that the number one sexual organ is the brain!

Whilst the four phase model proposed by Masters and Johnson laid the scientific foundations for our understanding of the human sexual response cycle, further studies showed that sexuality doesn’t always follow a linear trajectory, desire can spring up after the beginning of arousal, orgasm isn’t always the goal, and satisfaction can be at its max despite its absence.

What’s more, sexual experiences rely on sensory, emotional, psychological and identity-related dimensions that go beyond the strictly physiological framework. Spontaneous or reactive desire, the relational context, and the constant interaction between the brain, hormones, and emotions play a major role in sexual response. These models are descriptive rather than normative, and variability is the norm in sexuality. Frequency, intensity, duration and modalities vary according to the individual, age, context and health. It is important to explore your own sexual response and that of your partner in order to best adapt to each other's needs.