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The Science of Dreams: What Are They, And How do They Affect Sleep?

The Science of Dreams: What Are They, And How do They Affect Sleep?

Dreams are something that most of us take for granted. But dreaming is one of the most intriguing human phenomena there are.

People have been interpreting dreams for millennia, and in the last couple of centuries, neuroscientists and psychologists have been studying the science of dreaming to answer the age-old question: what are dreams, and why do we have them?

But even with the incredible advancements of the 21st century, scientists are still grappling with the mechanisms of dreaming and the reasons behind them.

Still, there is certainly a lot that we do know, so in this post, we’ll examine what the latest research has to say about dreams, including what they are and how they affect our sleep.

What Are Dreams?

what are dreams

Everybody dreams, although some of us dream more frequently and vividly than others.

But how do we define dreams?

Dreams are a state of sleep consciousness characterized by imagery, thoughts, sounds, and emotions.

In the 2014 book Dream Science: Exploring the Forms of Consciousness, psychologist J.F. Pagels describes dreams as “the cognitive state uniquely experienced by humans and integral to our creativity,  the survival characteristic that allows for the rapid change and innovation that defines our species and provides the basis for our art, philosophy, science, and humanity.”

Dreams often present as a mixture of lived reality and subconscious imagination. For example, they might feature friends, family, and colleagues, places we know, and events that have happened, alongside people we’ve never met before and places we’ve never been to.

Dreams can be mundane, pleasant, or arousing, or they can be alarming, stressful, and upsetting. And in the case of nightmares, they can be downright terrifying.

The human mind can experience a limitless array of scenarios and emotions within dreams, but often, they’re a distorted reflection of what is going on in our waking lives.

For example, a grieving person might dream of a deceased loved one, or someone under significant stress at work might dream that they’ve been fired or accidentally walked into the office with no clothes on.

This phenomenon is known as the ‘continuity hypothesis,’ which refers to the consistency between our waking and sleeping thought patterns.

But while some dreams reflect our waking world and are easy to interpret, others are much more mystifying.

Often, dreams manifest as irrational, disjointed, and bizarre, with no obvious meaning. These kinds of dreams have been an endless source of debate amongst psychologists ever since Sigmond Freud published his famous dream theory in 1899.

Freud theorized that dreams are a way for the subconscious to deal with repressed or undesirable emotions, impulses, and experiences. He also believed that the images and symbols contained within a dream, as bizarre as they may seem, can hold the key to understanding ourselves better.

But of course, not everyone agrees with Freud’s theory, and many scientists argue that most dreams are simply the brain engaging in imaginative play rather than a manifestation of our unconscious minds.

REM Sleep And Dreaming

REM Sleep And Dreaming

Dreams are most likely to occur during the REM stage of sleep when brain activity is at its highest level, but our muscles are deeply relaxed.

This is also the sleep stage where dreams are typically at their most vivid. That’s because, during REM sleep, the part of the brain responsible for rational thought and focus (the prefrontal cortex) slows down, while the parts responsible for instinct, emotion, and memory (the limbic system) and visual perception (the occipital lobe) become more active.

But while the REM sleep stage plays the most significant role in our dreams, dreaming can also occur during stage 2 non-REM sleep, particularly towards the end of the sleep cycle, when the brain alternates between NREM stage 2 and REM sleep.

Plus, it’s also possible to dream during the hypnagogic (falling asleep) phase and the hypnopompic (waking up) phase.

Remembering Dreams

Remembering Dreams

Some people dream more often and more vividly than others, but there’s also a wide variation in how well we remember our dreams.

You might not think you dream all that often, but perhaps you’re just not retaining the memory of your dreams for very long after you wake up.

Dream recall varies greatly between individuals, but generally speaking, the younger you are, the more likely you are to remember your dreams. Women are also more adept at dream recall, and bizarrely, so are people who live in big cities rather than small towns.

But despite these variations of dream recall, almost everyone can remember at least one or two significant past dreams; often ones they had many years ago. These are the dreams that left a lasting impact due to their intensity, vividness, and level of emotional response.

Lucid Dreaming

Lucid dreaming is the phenomenon of being aware that you are dreaming. During a lucid dream, the person can control their actions and responses and often even guide and manipulate the dream’s narrative.

In recent years, psychologists have linked the state of lucid dreaming to a process called metacognition, which is characterized by an ability to examine, understand and regulate one’s own thoughts.

The neural systems associated with metacognition are similar to those associated with lucid dreaming. So, people with heightened metacognitive abilities are thought to be more prone to lucid dreaming than others.



In the common vernacular, a nightmare refers to any kind of bad dream that feels scary, upsetting, or unpleasant. But scientifically speaking, bad dreams and nightmares are distinct from one another. Psychologists define a nightmare as a dream that is so disturbing that it causes you to wake up.

Most of the time, upon waking, the person remembers the content of their nightmare in vivid detail.

Often, waking brings a deep sense of relief when the person realizes that their nightmare was just that; a nightmare. But sometimes, the feelings of fear and anxiety can remain for several hours into the day.

The Common Features of Dreams

As we mentioned above, there are no constraints to our dreams, and the same limitless potential our brains experience in waking life also applies during sleep.

But that being said, there are some typical features that are commonplace in most dreams, including…

1. Imagery


Visual imagery is the most prominent dream feature of all, but while some people almost always dream in color, others exclusively dream in black and white.

Interestingly, blind people, including those who were born blind, also dream in visual images, although they tend to experience a higher proportion of features such as sound, smell, and taste.

2. Emotion

Dreams often elicit an intense emotional response, such as fear, anxiety, embarrassment, and surprise. Sometimes, these emotions are so strong that they even cause the dreamer to wake up mid-way through the dream.

3. Incoherence


Most dreams, even the most mundane, feature disjointed and illogical components. The natural laws of the universe don’t apply, and the person moves through time and place in an inconsistent fashion that’s impossible in the waking world. For example, settings suddenly shift, and objects can transform in bizarre and unrealistic ways.

4. Unawareness

Except in the case of lucid dreaming, most dreams are involuntary. The dreamer has no control of the dream narrative or their own actions, and they have no idea that what they are experiencing is actually a dream.

How do Dreams Affect Sleep?

How do Dreams Affect Sleep

Dreaming can be dramatic, exciting, and scary, so it’s reasonable to assume that vivid dreams could negatively impact a person’s sleep.

But actually, in most cases, the reverse is true. Dreaming is a good indicator of a healthy sleep cycle, and although it might not feel like rest, the dream process is an important component of our brain’s recovery and restoration.

It also enhances memory consolidation and helps us to become more creative, imaginative, and inspired in our waking lives, too.

The only exception is nightmares. As mentioned above, the official scientific definition of a nightmare is a dream so unpleasant that it causes the person to wake up. And as we all know, frequently waking up during the night plays havoc on our sleep cycle, leading to sleep deprivation and all of the negative effects that it can bring.


Dreams are one of the most mysterious and fascinating phenomena of the human condition, and there’s still so much we don’t know about what they are, how they function, and what purpose they serve.

But hopefully, this post has helped explain the current scientific understanding of dreams and dreaming and how they might impact our sleep.