Revealed: What it REALLY means when you cheat on your partner in your dreams (and what you must do the next morning) - by a top neurosurgeon in a fascinating new book

For me, as a neurosurgeon and a research scientist, dreams hold a particular fascination. Having spent my life immersed in the brain, I am not only infatuated by its infinite complexity but captivated to the point of obsession by what remains one of its greatest and most mysterious features — dreaming.

The source of dreams is the same as all mental activity, waves of electricity moving across the brain every moment we’re alive. Dreams are a product of normal brain function, and an extraordinary transformation that occurs in the brain each night when we sleep, following the circadian rhythms — the day-night cycles — that biologically govern all life.

Each night, our brains and bodies follow a repeating 90-minute cycle of light sleep followed by deep sleep, where the brainwaves are slow and rhythmic. The eyes start rolling under their lids and most of the muscles in the body become paralysed. When the eyes are fluttering under the eyelids, this is known as rapid eye movement or REM sleep.

REM sleep and dreaming are often described as synonymous, but this is inaccurate. We can dream in all stages of sleep. Dreaming is even possible without REM. But REM sleep is when the most intense and bizarre dreams occur.

There’s one way in which the dreaming life of men and women align - almost all of us cheat in our dreams

Dreams change as the night progresses. Early-night dreams tend to include more elements from our waking life. Dreams at the end of the night are more likely to be emotional and incorporate older autobiographical memories, and it’s these dreams just before we wake up that we’re most likely to remember.

The tenor of our dreams shifts, too. Dreams are more negative at the beginning of the night and become more positive as the night goes on.

Dreams affect us deeply because we experience them as real. The joy we experience in dreams is no different physiologically from waking joy, and so is the terror, frustration, sexual excitement, anger, and fear.

Run in our dreams and the motor cortex is activated, the same part of your brain that you’d use if you were actually running. Feel a lover’s touch in your dream, and the sensory cortex is stimulated, just as it would in your waking hours.

When we’re dreaming, the imagination is unfettered, free to find loose associations and connections in our memories

If we’re sleep deprived, the first thing we catch up on is dreaming. If we’ve had enough sleep but are dream deprived, we will immediately start dreaming as soon as we fall asleep. There is much focus these days on the need for sleep to be healthy, but it may be that it’s not the sleep we really need, but the dreams.

Erotic dreams are part of human nature. You couldn’t stop them if you wanted to. Menopause does not extinguish them, nor does chemical castration. It doesn’t matter whether you are sexually active, celibate, married, or single. Erotic dreams are universal.

In surveys, sexual dreams were reported by 90 per cent of Brits, 87 per cent of Germans, 77 per cent of Canadians, 70 per cent of Chinese, 68 per cent of Japanese, and 66 per cent of Americans. An estimated one in 12 of all dreams contains sexual imagery, the commonest being, in order, kissing, intercourse, sensual embrace, oral sex and masturbation.

They can leave us flushed with pleasure or filled with jealousy. They are often unsettling. What does it mean to have a sexual dream about an ex? What if your partner has an erotic dream about someone else? Do they reveal anything about our true desires?

Single men have a higher frequency of erotic dreams compared to men in stable partnerships. On the other hand, women report more sexual dreams when they miss their partners or at the height of a love affair, while men report no similar surge in erotic dreams in those scenarios.

But there’s one way in which the dreaming life of men and women align — almost all of us cheat in our dreams.

What should we make of this? As creators of our dreams, we select the cast of our nocturnal dramas, the stage, and the action. The dreams we conjure are our own sensual productions. Wouldn’t a dream where we cheat on a partner be a sign we are looking to be unfaithful, or at least open to it? Surely an erotic dream is our libido unfiltered and unleashed. If not, then what could it possibly be?

All dreams are the product of the Imagination Network in our brains, unbound by the rules and logic of our waking life. When we’re dreaming, the imagination is unfettered, free to find loose associations and connections in our memories. It can lead us to think about the people in our lives in surprising, disturbing and even erotic ways.

Because the logical Executive Network in our brains is shut down during dreaming, we can’t stop these erotic flights of fancy before they take off. They are also free from judgment — even our own.

In erotic dreams we are liberated to imagine sexual encounters that would be taboo or inconceivable in our waking lives. They will probably not involve our current partner. Instead, we have much more of an inclination toward bisexuality and novel sexual interactions generally.

So, what do erotic dreams really mean? Researchers have conducted surveys on sexual activity, asking how happy people are in their romantic relationships, whether they have jealous personalities and how these personal characteristics impact on their dreams. They tried to provoke erotic dreams by asking participants to watch pornography.

Erotic dreams are part of human nature. You couldn’t stop them if you wanted to

What they found was surprising. Erotic dreams are not tied to how much sex you are having in your waking life, nor to whether you masturbate. They are not even connected to how much pornography you consume. The best predictor of erotic dreaming seems to be how much of our waking life we spend day-dreaming about erotic fantasies. This makes us more open to erotic dreams at night.

However, there’s one very important difference between daytime fantasies and erotic dreams. When we’re fantasising during the day, these erotic thoughts are reined in by the rational part of our brain, the Executive Network, which constrains sexual desires. This moderating influence is gone when we dream, allowing our erotic dreams to be wildly creative and exploratory.

From this I conclude that erotic dreams are more like thought experiments than a sign of the type of latent desires that Freud wrote about. We can switch genders or become bisexual, even if it never crosses our minds during the day or in our most liberated fantasy.

Erotic dreams are undeniably deeply pleasurable. In a survey of university students in China, they responded overwhelmingly to the following statements:

• I hope to immerse myself in a sexual dream and never wake up.

• I feel lucky to have sexual dreams.

• I am sad after waking up from a sexual dream because I find it was just a dream.

How can it be that imagined sex carries such emotional, libidinal weight? These are, after all, solitary, imagined events outside of our conscious control. It seems implausible they could mean so much to us, but they do.

The answer is that erotic dreams have this kind of power because the brain is our most powerful sex organ.

Erotic dreams do more than reflect or release our emotions, imagination and libido. They can deliver the same intense pleasure as actual sex. They might even be better than the real thing.

In erotic dreams, the brain is not receiving any signals of touching or being touched. Erotic dreams occur in the brain alone. Even so, more than two-thirds of men and more than a third of women say they’ve experienced orgasms simply as the result of a dream.

Consider what is happening in the brain during the physical act of sex. Sexual activity draws upon every bit of our central nervous system, which send signals to the brain during sex. The crucial thing is that the brain interprets them.

You can be touched in the same place, with the same pressure, in the same fashion, and your brain can neglect it as something insignificant. Or interpret it as a frisson or a caress.

In which case, it doesn’t matter where you’re touched. Touch can turn erotic anywhere on the body. The brain alone is what determines sexual significance, causes us to feel attraction (or not), our breathing to quicken (or not), our heart to race (or not), and for us to become aroused (or not).

In erotic dreams, however, the body is silent. The peripheral and autonomic nervous systems are not sending signals to the brain. During our most vivid dreams, our muscles for coordinated movement are essentially paralysed below the neck. The brain is not reacting to any signals from the body but acting out its own imagination.

As erotic dreams show us, the brain doesn’t need the rest of the body at all. It can create its own stage, characters, and action. The mind is its own erogenous zone, and dreams can pursue the pleasures of the flesh without any flesh other than the brain itself.

If this all sounds impossible, think about other aspects of how we perceive and respond to the world. Consider sight, for example. The lens and cornea work together to focus light on the retina at the back of the eye but it is the brain that processes what is seen into a single, clear view of the world. Without the brain, we do not see.

Erotic dreams are the same. With no sensory inputs at all, the brain creates and perceives full-bodied pleasure. Sex and other erotic pleasures we experience in our dreams are not felt any differently because, as far as the brain is concerned, there is no difference. The brain does not experience real orgasms or fake ones; to the brain, they are all real.

And since our unrestrained emotional system when we’re dreaming can exceed levels we reach in waking life, it’s reasonable to conclude a dream orgasm can take us to heights waking sex cannot.

What then do erotic dreams reveal about our relationships? The science suggests that dreams of infidelity are unlikely to be a signal we want to be unfaithful. They are much more likely to be the brain’s Imagination Network in action. Cheating on a partner in a dream may simply be a sign of curiosity and normal sexual arousal, rather than a desire to stray from the relationship.

Nor are dreams where we explore a different sexual orientation a sign of a secret or repressed desire. This, too, appears to be more curiosity, libido, and imagination at play.

Even so, erotic dreams have plenty to tell us about both the health of our current romantic relationships and how well we have got over former romantic partners, but perhaps not in the way we may expect.

Erotic dreams can elicit strong feelings of desire, jealousy, love, sadness, or joy powerful enough to affect how we feel about our partner the next day. Just like the sensations in the dream, the brain perceives the emotions as real. Researchers have found conflict with a partner in a dream tends to result in conflict the following day.

In unhealthy relationships, infidelity dreams are associated with decreased feelings of love and intimacy in the days that follow. In healthy relationships, infidelity dreams don’t have much of an effect at all.

How we feel about a partner during our waking hours can also affect our dreams. Feelings of jealousy during the day can produce dreams of infidelity, which in turn affect a dreamer’s behaviour toward their partner. In these cases, dreams and reality appear to feed on each other in a negative loop.

It’s likely that negative emotions in an erotic dream about a partner could serve as an important signal of how you feel about that person. But the emotions associated with erotic dreams are far more important than the dream narrative itself.

If you or your partner have a dream of being unfaithful, this is not a sign of anyone’s true desires. Even though you may wake up unsettled or upset, remember that dreams are designed to make us think divergently, including about our sex lives. What really counts is not our erotic dream narrative or our partner’s but how we react to these dreams.

Ex-partners can and do show up in dreams long after they have ceased being a part of our lives. While dreams of current partners often involve doing something together, dreams of ex-partners are more likely to be erotic. 

You may be tempted to conclude this means we’re longing for an ex. But based on a number of studies, the opposite is usually true. These dreams appear to be helping us to get over our former partners. They may simply be a way of processing the emotions of a break-up.

There may, though, be a much more fundamental purpose to erotic dreams – as a way our brains have evolved to prepare and protect humanity for procreation.

My belief is that erotic dreams are a cognitive platform on which sexual fluidity and ingenuity are created, ‘wildcards’ that could help our species to survive by giving us a plasticity and flexibility of desire so we have the means to reproduce ourselves even in the most extreme circumstances.

If, say, half our tribe was wiped out by disease, erotic dreams like these could have readied our ancestors for new engagements and entanglements within our tribe. This may also help explain why erotic dreams tend to stick close to home. The characters in our erotic dreams are rarely inventive but the interactions often are.

In this way, erotic dreams are more than our true desires: They are the embodiment of desire itself. They prime us for sexual exploration and a breadth of sexual impulses. This makes sense when we remember the essential biological imperative of life is to survive long enough to reproduce.

Our brains have developed so they are highly tuned to erotic thinking. Fantasy, erotic dreaming — and ultimately our sexuality — arose from the essential drive to procreate.

Adapted from This Is Why You Dream by Rahul Jandial (Cornerstone, £18.99). © Rahul Jandial 2024. To order a copy for £17.09 (offer valid to 11/05/24; UK P&P valid on orders over £25) go to mailshop.co.uk/books or call 020 3176 2937.

Why so many dream of sleeping with Halle Berry

In dreams, we are free to be with anyone we want. Given this freedom, whom do we desire? This may surprise you, but we don’t conjure the ideal sexual mate to participate in our erotic dreams, some idealised chimera blending desirable characteristics into the ultimate fantasy.

We typically imagine someone closer to home, often someone prosaic - possibly even repellent - from our waking life. That’s why erotic dreams tend to involve someone familiar: ex-partners, our bosses and co-workers, friends and neighbours, even family members when we’re younger. 

Four out of five erotic dreams involve someone well-known to the dreamer, and these erotic encounters generally occur in a familiar place.

Scientific research has discovered that we have individual neurons in our brains dedicated to people and places most familiar to us. This can include famous people such as Halle Berry

Erotic dreams can also involve celebrities and other public or historical figures – for which we have something dubbed the Halle Berry neuron to thank. Scientific research has discovered that we have individual neurons in our brains dedicated to people and places most familiar to us. This includes famous people and places.

At Leicester University, a study of the brains of patients suffering epileptic seizures identified individual neurons that responded selectively to pictures of celebrities. One patient reacted to pictures of American actor Halle Berry; another patient had a similar response to Jennifer Aniston.

This is because celebrities have literally taken root in our neural architecture, as familiar to us as a long-time friend. Erotic dreams of sex with celebrities constitute dreaming of people we know.

 What happens when we dream

To experience the wild, visual narratives of dreams, three things have to happen. The first is that the body becomes paralysed. Neurotransmitters switch off the motor neurons that activate our muscles, locking down the body and allowing us to dream safely. Otherwise, we would be acting out our dreams.

Unable to move, we are a captive audience, safely locked into the theatre of our dreams for a show we’ve created for an audience of one.

If you shine a bright light into a dreamer’s eyes, they are blind to it. When we dream, the brain is alive with electrical activity, even though it is largely shut off from the world around us. It’s like a film playing in a dark cinema, a film in which we are more leading actors than directors.

The second prerequisite for dreaming is that the brain’s Executive Network – the structures responsible for logic, order, and reality testing - must turn off, enabling us to ignore the normal rules of time, space and reason and allowing us to accept our dreams’ improbable plots unquestioningly. This gives dreams both their power and their unique character.

The third thing that has to happen when we dream is that we activate widely those dispersed and disparate parts of the brain collectively called the Imagination Network. This creates something from nothing, fashioning stories from thin air, allowing us to ‘see’ without receiving visual information from the outside world.

Free-flowing stories are created from nothing and yet are imbued with meaning. In our dreams, we produce compelling narratives from distant memories, recent and planned events, emotions, snippets of things we’ve seen online or read in a book, and other bits and pieces from our lives that we stitch together into a story.

Little is off limits as our dream selves act and react and the unfettered nature of dreaming is able to take us to places when we’re asleep that are impossible in our waking life. It’s quite a production. We may respond in ways that are different from our waking self. We may be stronger or weaker, more assertive or more passive.

Yet, as wild and untamed as dreams are, with implausible situations and irrational jumps in time and place, there are limits. Even dreams have rules. As magical as dreaming seems to be, dreams hew to certain boundaries, existing within the framework of their neurobiological origins.

For example, you are unlikely to dream of a mobile phone riding a horse, and it’s extremely rare for objects to turn into people in our dreams, or for people to transform into animals.

When objects turn into other objects, they are likely to turn into something similar. A car turns into a bike, a house into a castle. Jumps follow the semantic maps in our memory, tending to stay in the same clusters. As far as we can tell, this is the way dreams have been for as long as humans have been recording them.

Which is why, despite massive changes in the way we live, the content of dreams has changed little through the ages. Many common dreams today are no different from those dreamed in Egypt in the time of the pharaohs or Rome in the time of Caesar.

Sleep disorders recorded in China more than 1,800 years ago include dream flying, dream falling, and night terrors. Sound familiar?

Dreams are also remarkably similar all over the world, regardless of where we live, what language we speak, our wealth or standing. A recent survey of Chinese students listed their five commonest dreams as: 1. Teachers; 2. Being chased; 3. Falling; 4. Arriving too late (eg, missing a train); 5. Failing an examination. For German students, it was virtually the same.

Given this continuity of dreams across time and place, it seems reasonable to conclude that the characteristics and contents of dreams are baked into our DNA, a function of our neurobiology and evolution, largely immune from differences in culture, geography, and language.