Psychology Topics > Consciousness and Sleep


We're doing things a little different with this topic. Rather than having just one introduction section followed by key figures and concepts, we're giving you overview sections for numerous topics within Consciousness and Sleep, dive into topics such as altered states of consciousness and the different stages of sleep, then cover some of the key theorists. And of course, we have several videos that are interesting, educational, and fun.

Consciousness & Sleep

States of consciousness are a subjective perceptual experience and therefore difficult to define. Some people define the difference between consciousness and unconsciousness by whether the person's eyes are open or shut. According to the Webster Dictionary, consciousness is defined as the quality or state of being aware especially of something within oneself. William James, a key figure in the study of consciousness, believed that consciousness consisted of a steady stream of thoughts, emotions, and perceptions.

consciousness can also be thought of as two separate factors, monitor and control. Monitoring refers to the ability to perceive one's environment, survey potential problems, identify goals and make decisions. Attention (or focusing one's awareness on any thought or outside event) is another word for monitoring.

In contrast, control is one's ability to organize thoughts and utilize behaviors to complete tasks. In other words, monitoring allows a person to survey the environment and make decisions. Control allows that person to act on those decisions.

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Alternate States Of Consciousness

If states of consciousness were on a continuum, with consciousness at one end and sleep at the other end, hypnosis and meditation would fall in the middle. Hypnosis is a state of consciousness, which is characterized by deep relaxation and high suggestibility. You've probably seen people get hypnotized and then act in bizarre ways such as clucking like a chicken - although this is certainly possible, it's not the purpose of hypnosis (at least not for us). Rather, hypnosis has real therapeutic value.

In therapeutic situations, hypnosis is utilized to help people quit smoking or even undergo surgery without anesthesia. In order to accomplish this, the therapist "suggests" to a hypnotized individual that they will be relaxed and numb throughout their body during a medical procedure. The therapist would have to repeat this process on more than one occasion to reinforce the suggestion. The more times a hypnotherapist reinforces a suggestion, the stronger it will be and the more likely it will work.

Hypnosis has been helpful for some people that have severe allergic reactions to anesthesia or other pain medications. It allows these people to undergo painful procedures without anesthetic and still not feel any pain. Hypnosis has also been used to help people lose weight and stop smoking.

In the media, hypnosis has usually been portrayed as a technique for unlocking unconscious memories of traumatic events. Many therapists have stopped this practice, however, because of the risk of false memory syndrome and the Misinformation Effect. As the name suggests, false memory syndrome refers to clients who have memories of childhood abuse but were never abused. It is thought that these false memories were implanted intentionally or unintentionally by therapists who were using hypnosis to uncover hidden memories.

Although hypnotherapists can make these "suggestions," it should also be noted that even individuals under hypnosis will not complete any task that is against their ethical or moral code. An example of this is hypnotizing someone and then suggesting to them that they go kill someone. This scenario may make a good movie, but in reality, it would not work.

Meditation is another alternate state of consciousness that consists of deep relaxation in which the individual focuses attention on a single thought, word, or image. A word or sound in hypnosis is called a mantra. Meditation also sometimes referred to as "mindfulness." This means that the individual is focusing his or her awareness on the "here and now," i.e. focusing on what is being experiences in the present moment. Meditation also involves concentration on breathing and is thought of as a uniquely spiritual experience for each individual. Unlike hypnosis, it does not include high suggestibility.


At the far end of the consciousness continuum are unconscious states such as sleep. Sleep, like other states of consciousness, is unique to each individual. The stages of sleep, however, follow a similar pattern. These stages (as well as other states of consciousness) are characterized by different brain waves: Beta; Alpha; Theta; and Delta. Beta waves typically occur during wakeful states. Alpha waves are correlated with forms of meditation, hypnosis, and light sleep, while both Theta and Delta waves occur in deep sleep states.

Stages of sleep (Stages 1 - 4 are NREM)

  • STAGE 1: Person transitions from being awake to being asleep, has increased Theta waves and decreased Alpha and Beta waves. It typically takes the average person 30 minutes to move to stage 2 of sleep. It is easy to awaken from this stage.
  • STAGE 2: Person begins to experience sleep spindles, K-complexes, Theta, and Delta waves. These are all waves that can be identified via Electroencephalogram (try saying that 3 times fast) also called an EEG. An EEG is a device that measures brain electrical activity in the form of brain waves mentioned above. During this stage, our heart rate and breathing slows, and our body temperature decreases.
  • STAGE 3: Person has increased Delta waves and is now in a deep sleep.
  • STAGE 4: This is a very deep sleep also characterized by increased delta waves.
  • REM: Person enters REM (rapid eye movement) sleep. During this stage, the eyes move rapidly back and forth under closed eyelids. It is thought that this REM movement aids the processing of information and experiences. This is also the stage in which dreaming occurs. In this stage, our heart rate and breathing quickens, our blood pressure rises and our body temperature fluctuates. Our brain activity is almost the same as when we are awake, however, there is a temporary paralysis to our body so we are unable to move until we move to a different stage of sleep. Current researchers are also beginning to discover that dreaming occurs in other sleep stages but these dreams are not as vivid as REM dreaming.


As a person sleeps, he or she alternates between stages. Whereas in the beginning of sleep, a person spends more time in the first 3 stages of sleep, by the end, he or she spends the most time in REM sleep. REM sleep generally begins after the first 90 minutes of sleep and then reoccurs throughout the night as we alternate between stages.

There are many theories about why we sleep, but the reality is we don't know with certainty. Here are some possible explanations of why we sleep.

  • Restorative and Repair: sleep restores our body physiologically and REM restores us mentally. The body also increases cell division are repair while the body is at rest.
  • Evolutionary theory: this is an adaptive theory that suggests we need to conserve energy, therefore, we sleep at night because earlier man would have been more vulnerable to predators if they were to sleep during the day.
  • Information consolidation: this theory states that we use sleep to process experiences and information that we learned during the day. In this theory, sleep is also believed to help solidify the transfer of information to long term memory.
Sleep Deprivation

Sleep deprivation is characterized by irritability, exhaustion, impaired immunity, increased stress, and psychotic behaviors (e.g. hallucinations) after not sleeping for 3 days. REM appears particularly important. Scientists that monitored patients via EEG and deprived them of REM sleep (waking the individual once they entered REM sleep) found that REM deprived individuals entered REM stage sleep sooner and spent a greater percentage of time in REM sleep than non-REM deprived individuals. In some situations, however, such as depression, REM deprivation can be beneficial and actually alleviate depressive symptoms. REM deprivation is also correlated with the development of Parkinson's and related disorders.

The amount of sleep we need differs from person to person. On average, a adult needs between 7-8 hours of sleep each night. More specifically, the amount of sleep we need is calculated from 2 factors; basal sleep need, and sleep debt. Our basal sleep need is the amount of sleep our bodies need on a regular basis. Our sleep debt is the amount of sleep we have lost due to various causes such as sickness, awakening in the middle of the night, sleep habits, etc.. If a person has an unresolved sleep debt, he or she will feel more sleepy during the day. This accounts for why a person will sleep longer after going 24 or more hours without sleep.

Relevant Tests Used In Sleep Studies

Electroencephalogram (EEG)
This device measures the electrical activity of the brain. Specialists use this device to determine which stage of sleep a person is in. The EEG measures the frequency of brain waves (i.e. how many times the wave occurs in a specific time period) and the amplitude of brain waves (i.e. the size of the wave.)

Electrooculagram (EOG)
This device measures eye activity. During different stages of sleep, our eyes move in distinct ways. For example, during slow wave sleep (SWS), we have slow, rolling eye movements, However, during REM sleep, our eye movements are much more rapid and occur in a sharp, back and forth way. The EOG is a vital tool for identifying REM sleep since the EEG in REM, wake and stage look so similar. But, when we combine the EEG and EOG it is easy to see the differences.

Electromyogram (EMG)
This device is used to measure the muscle activity that occurs during sleep, and is particularly helpful when attempting to identify REM sleep. During REM sleep, humans experience a type of temporary paralysis during which the EMG drops to almost nothing (close to a flat line).

Electrocardiogram (ECG or EKG)
The electrocardiogram is a measure of heart muscle contractions.

Sleep Disorders

A sleep disorder characterized by "sleep attacks," an immediate entry of a conscious individual into the REM stage of sleep. This disorder is very dangerous because these "sleep attacks" occur without warning and could occur during dangerous activities such as driving.

A sleep disorder characterized by difficulties falling asleep, staying asleep, or both. People with insomnia are also excessively tired during the day.

Night Terrors
This disorder is seen most frequently in children and consists of the child awakening in the night with intense panic or autonomic arousal. A child with this disorder may awaken screaming, but then falls back asleep. Upon awakening, he or she will have no memory of the event.

Nightmares are dreams characterized by extreme terror and panic. They are usually indicative of traumatic events in the individual's life.

Sleep Apnea
A person with sleep apnea stops breathing while they sleep due to obstruction to their airway. This causes their body to reflexively awaken in order to breathe again. The individual may or may not be aware of these awakenings which can occur hundreds of times each night.

Sleep Walking
This disorder is pretty self-explanatory.


Our discussion of conscious and unconscious states would not be complete without mentioning comas. A coma is a profound state of unconsciousness in which the person does not awaken or respond normally to pain, light or sound. There are many causes of comas such as brain damage, stroke, metabolic disorders, intoxication, and other problems with the parts of the brain responsible for sleep regulation. Individuals in a coma are at risk of asphyxiation because the muscles in the neck and airway become so relaxed that the airway closes. Medical doctors prevent this by inserting a tube to keep the airway open.

Comas usually last a few days to a few weeks. Doctors use certain assessments to determine whether the person has irreversible brain damage or is expected to recover. One of these assessments is called a Glasgow Coma Scale (GCS). The GCS is a 3-15 point scale (15 being the best). People are rated according to 3 categories, e.g. eye response, verbal response, and motor response. A score of 13 is considered minor damage. A score of 9 is moderate damage. A score below 9 is severe damage.

Key Figures & Theories

Rene' Descartes
Rene' Descartes was a philosopher who attempted to explain the concept of consciousness through his statement "cogito ergo sum," which means, "I think, therefore, I am." He believed that anything that could think was "conscious." Therefore, he believed animals were not conscious because they could not think as humans can.

John Locke
John Locke was influential on the subject of consciousness for his theory of the "self." He expounded on Descartes belief that thinking was vital for consciousness and stated, "that conscious thinking thing, (whatever substance, made up of whether spiritual, or material, simple, or compounded, it matters not) which is sensible, or conscious of pleasure and pain, capable of happiness or misery, and so is concerned for itself, as far as that consciousness extends." Locke was also notable for his theory of tabula rasa or "blank slate." He believed that infants were blank slates and were shaped by their experiences in life. This idea that experiences were vital to the child's developing personality was central to the field of psychology.

Sigmund Freud
Freud's contributions to the study of sleep and consciousness involved the importance of dream analysis. Freud analyzed dreams according to manifest content (literal storyline) and latent content (what the dream meant symbolically). Freud believed that dreams reflected unconscious experiences, wishes and desires of the individual. Freud also wrote The Interpretation of Dreams in 1899. In this book, Freud illustrated his theories of how and why he believed dreams were formed.

Carl Jung
Like Freud, Carl Jung also believed that dreams were a window to the unconscious mind and were filled with hidden meanings. He believed that dreams could be classified according to two categories, objective and subjective. Objective dreams were a picture of the individual's day-to-day life. Subjective dreams reflected the individual's inner life or unconscious world. Another important aspect of Jung's beliefs about dreams involved archetypes. Archetypes are like models, prototypes, or stereotypes that are used as a structural component to a developing personality. Jung stated that a person's archetypes were visible through their dreams. The archetypes that Jung described were the Self, Shadow, Anima (feminine characteristics), Animus (male characteristic), and Persona (the image an individual allows the external world to see.) Jung stated that the hidden meaning in dreams was an important part of psychoanalysis.

Rosalind Cartwright
Rosalind Cartwright, another dream expert, believes that dreams are the body's way of reviewing, revising, rehearsing, and repairing present and past experiences. One of her unique contributions to dream research considers how dreams are used to regulate moods. She stated that individuals who are in a bad mood when they go to sleep often wake up in the morning with a more positive attitude. She stated if people were not awaking refreshed and feeling better emotionally, their dreams would reveal issues that they were having difficulty processing. Cartwright also found that individuals in crisis who recovered quickly also dreamed longer and sooner in their sleep cycles than individuals who did not recover as rapidly.

David Chalmers
David Chalmers is noteworthy for his theories of consciousness. He believes that subjective experiences and feelings have not been explored adequately in theories of consciousness. Therefore, he proposes that there are two types of consciousness, the objective physical side and the subjective experiential side. He argues against physicalism, the belief that all things that exist are the result of physical processes. Chalmers is also known for his "philosophical zombie" argument. A philosophical zombie relies solely on the objective physical side of consciousness and cannot experience subjective experience. Chalmers stated "Zombies are probably not naturally possible: they probably cannot exist in our world, with its laws of nature." Despite his statement, however, he argues that zombies can logically exist. David Chalmers is currently the Director of the Centre for Consciousness at the University of Arizona. His notable works are "Facing Up to the Problem of Consciousness" (1995), and "The Conscious Mind" (1996).

William Dement
William Dement is a well known sleep researcher who founded the American Sleep Disorders Association. Dement used the EEG to monitor individual sleep cycles throughout the night which led to Dement's discovery of the 5 sleep stages. He also developed the Multiple Latency Sleep Test which is a test used to measure daytime sleepiness. Today, he currently teaches at Stanford School of Medicine.

Bernard Baars
Bernard Baars believes that an important aspect of consciousness is the individual's ability to solve problems in new ways that are not yet habitual. An action or decision that is habitual is not conscious but performed by the unconscious mind. For example, learning to ride a bike is a task that requires the attention of our conscious mind. After we learn to ride a bike, however, we no longer need to focus attention or be conscious of the processes involved in riding a bike (e.g. balance, speed, etc.)

Baars is also notable for his 9 functions of consciousness.

  • Definition and contexts
  • Adaptation and learning
  • Editing, flagging, and debugging
  • Recruiting and control function
  • Prioritizing and access control
  • Decision making and executive function
  • Analogy-forming function
  • Metacognitive of self-forming function
  • Auto-programming and self-maintenance