5 missions. Guess, learn, then check. Your place is saved.
Mission 1You dream mostly in one stage of sleep. What are the others for?
Mission 2Long flight: your body says 3 a.m. at breakfast. What resets it?
Mission 3Lying awake at 3 a.m.: is it the body, the bedroom or the brain?
Mission 4Freud thought every dream is a disguised wish. Disguised from whom?
Mission 5Brain busy, body paralysed: why does REM sleep turn into a story?
The specification points and sources are listed under the lesson: see Sources.
Mission 1
You dream mostly in one stage of sleep. What are the others for?
Make a guess: You dream mostly in one stage of sleep. What are the others for?
Sleep and dreaming · the sleep cycle
Why do we need sleep?
Sleep is an active state with three big benefits:
Healthy brain: sleep clears waste from the brain and strengthens the pathways that store new memories.
Physical repair: in deep sleep the body repairs tissue, builds bone and muscle and supports the immune system.
Emotional stability: sleep, especially REM, helps you process emotions. After poor sleep people are more irritable and less able to cope.
Sleep and dreaming · the sleep cycle
Four stages, light to deep
Stage
What happens
Stage 1
Light sleep as you drift off; muscles relax; easily woken
Stage 2
Heart rate and temperature fall; brief bursts of activity called sleep spindles
Stage 3
Deeper sleep; slow delta waves appear
Stage 4
Deepest sleep; mostly delta waves; very hard to wake
These are non-REM (NREM) stages. Your spec calls them the four sleep stages; REM sleep follows them.
Some sleep scientists now merge stages 3 and 4 into one stage. In the exam, use stages 1 to 4 plus REM.
Sleep and dreaming · the sleep cycle
REM sleep
REM stands for rapid eye movement: the eyes dart about under closed lids.
Brain activity is fast and close to waking levels.
Breathing and heart rate become quicker and less regular.
The arm and leg muscles are temporarily paralysed, so you can't act out dreams.
Dreaming happens mostly in REM. Some dreaming also occurs in NREM sleep, but it is usually less vivid.
Sleep and dreaming · the sleep cycle
The sleep cycle
One sleep cycle: stages 1, 2, 3, 4, back up through 3 and 2, then REM.
A cycle lasts about 90 minutes, and a night usually has 4 to 5 cycles.
Early cycles contain the most deep sleep (stages 3 and 4).
Later cycles contain less deep sleep and longer REM periods; the last one can last up to an hour.
Quick check
?A sleep lab records a volunteer two hours after she falls asleep. Her brain shows mostly slow delta waves, her eyes are still, and a loud noise does not wake her. Which stage is she in?
Calculate
?A teenager sleeps for 7.5 hours. If each sleep cycle lasts 90 minutes, how many complete cycles does she pass through?
Sort it
?Is each feature typical of REM sleep or of non-REM sleep (stages 1 to 4)?
Tap a statement, then tap the group it belongs in. Then press Check.
Mission check
?You dream mostly in one stage of sleep. What are the others for?
Dreaming happens mostly in REM, but the other four stages matter too. Stages 1 and 2 take you down into stages 3 and 4, the deepest sleep, when the body repairs tissue and builds bone and muscle and the brain clears waste and strengthens memories. You repeat this cycle about every 90 minutes.
Mission 2
Long flight: your body says 3 a.m. at breakfast. What resets it?
Make a guess: Long flight: your body says 3 a.m. at breakfast. What resets it?
Sleep and dreaming · body clocks
Bodily rhythms
Your body runs on cycles called biological rhythms.
A circadian rhythm repeats about every 24 hours. The sleep–wake cycle is one: you feel sleepy at night and alert by day.
Body temperature also follows a circadian rhythm, lowest in the early morning.
An ultradian rhythm repeats more than once in 24 hours. The sleep cycle (about 90 minutes, several times a night) is ultradian.
Sleep and dreaming · body clocks
The clock inside you
An internal influence on sleep is a body clock that keeps rhythms going without outside cues.
As it gets dark, the brain signals the pineal gland to release the hormone melatonin, which makes you sleepy.
Melatonin levels are high at night and low in the morning.
Sleep and dreaming · body clocks
Cues from outside
An external influence is a zeitgeber ("time-giver"): an environmental cue that resets the body clock daily.
Light is the most important. Light reaching the eyes stops melatonin release and shifts the clock.
Others: meal times, alarm clocks, social routines.
Jet lag and shift work: the clock is out of step with these cues.
With no zeitgebers, rhythms continue but drift from 24 hours.
Key studySleep and dreaming · body clocks
Siffre (1975)
Aim
To see how the sleep–wake cycle behaves with no zeitgebers such as daylight or clocks.
Method
Case study of Siffre himself, aged 33, alone in a Texas cave for about six months in 1972, with no clocks or daylight. He phoned the surface team on waking and before sleeping, and they switched his lights on or off. His heart, brain and muscles were monitored.
Results
His sleep–wake cycle varied from about 18 to 52 hours, with long spells of about 48 hours. His memory and mood got worse.
Conclusion
Without zeitgebers the body clock still runs but drifts from 24 hours.
Strength
Detailed physical data over a long period.
Weakness
One participant, so results may not generalise.
Sort it
?Is each one an internal or an external influence on sleep?
Tap a statement, then tap the group it belongs in. Then press Check.
Quick check
?Jo works night shifts and tries to sleep at 9 a.m. in a bright bedroom. She feels tired but keeps waking. What is the best explanation?
Sort it
?Evaluating the explanations. Is each point a strength or a weakness?
Tap a statement, then tap the group it belongs in. Then press Check.
Mission check
?Long flight: your body says 3 a.m. at breakfast. What resets it?
Your body has its own roughly 24-hour clock, and the pineal gland releases melatonin when that clock says it is night. Light is the main zeitgeber: daylight at the new time stops melatonin release and gradually shifts the clock until it matches local time.
Mission 3
Lying awake at 3 a.m.: is it the body, the bedroom or the brain?
Make a guess: Lying awake at 3 a.m.: is it the body, the bedroom or the brain?
Sleep and dreaming · sleep disorders
What is insomnia?
Insomnia means regularly having problems sleeping.
Symptoms: finding it hard to fall asleep, waking in the night and lying awake, waking too early, and still feeling tired, irritable or unable to concentrate during the day.
Primary insomnia has no other cause; secondary insomnia is a symptom of another problem, such as pain or depression.
Sleep and dreaming · sleep disorders
Why do people lie awake?
Stress and anxiety activate the sympathetic nervous system: heart and breathing speed up and the mind races, so the body is too aroused to sleep.
The bedroom: noise, light, heat, an uncomfortable bed.
Lifestyle: late caffeine, a large meal, late gaming, jet lag, shift work.
Health: pain or illness.
Evaluation: poor sleep also raises stress, so cause and effect are hard to separate.
Sleep and dreaming · sleep disorders
Narcolepsy
Narcolepsy: a rare, long-term brain disorder affecting control of sleep and waking.
Symptoms: extreme daytime sleepiness, sudden sleep attacks, cataplexy (muscle weakness triggered by emotion, such as laughter), sleep paralysis.
Explanation: low hypocretin, a brain chemical that keeps us awake; the immune system may attack the cells making it.
Genes: a linked genetic marker exists, but many people without narcolepsy carry it.
Quick check
?For two weeks before his exams, Sam lies awake for an hour or more after going to bed. His heart races and he keeps going over his revision. Which explanation fits best?
Sort it
?Is each symptom more typical of insomnia or of narcolepsy?
Tap a statement, then tap the group it belongs in. Then press Check.
Mission check
?Lying awake at 3 a.m.: is it the body, the bedroom or the brain?
It can be any of the three, and they often combine. Stress arouses the body through the sympathetic nervous system, a noisy or bright bedroom makes sleep harder, and caffeine, screens, pain or illness all play a part.
Mission 4
Freud thought every dream is a disguised wish. Disguised from whom?
Make a guess: Freud thought every dream is a disguised wish. Disguised from whom?
Sleep and dreaming · Freud's theory
The unconscious mind
Freud said most of the mind is unconscious: thoughts, memories and desires you are not aware of.
Repression pushes disturbing or unacceptable wishes out of the conscious mind into the unconscious.
Repressed wishes don't disappear. They push to be expressed.
Freud called dreams "the royal road to the unconscious".
Sleep and dreaming · Freud's theory
Wish fulfilment: two layers of a dream
Wish fulfilment: Freud claimed every dream fulfils a wish, often a repressed one.
In sleep the mind's guard relaxes, so wishes can surface.
A raw wish would shock the dreamer awake, so it is disguised. Freud called dreams the guardians of sleep.
Manifest content: the dream as you remember it, its story, people and places.
Latent content: the hidden meaning underneath, the real wish.
Sleep and dreaming · Freud's theory
Dreamwork
Dreamwork turns the latent content into the manifest content:
Condensation: several ideas are squeezed into one image.
Displacement: a feeling is moved onto a less important person or object.
Symbolism: the wish appears as a symbol.
Secondary elaboration: the mind stitches the pieces into a story.
In dream analysis, the therapist works backwards from manifest to latent content.
Key studySleep and dreaming · Freud's theory
Freud (1909) Little Hans
Aim
To explain a five-year-old boy's phobia of horses, using his dreams and fantasies.
Method
Case study of one boy, Hans. His father, a Freud supporter, recorded Hans's behaviour, dreams and fantasies and sent them to Freud by letter.
Results
Hans feared horses, especially the black around their mouths and their blinkers. He described a big giraffe and a crumpled one: he took the crumpled one away and the big one called out.
Conclusion
The horses stood for Hans's father; the giraffes showed a hidden wish to have his mother to himself (the Oedipus complex).
Strength
Rich, detailed data about one child over time.
Weakness
Data came from a father who supported Freud, so may be biased.
Quick check
?Maya dreams she misses a train that leaves without her. Her analyst says the dream really shows a hidden wish to leave home. In Freud's terms, the hidden wish is the dream's…
Sort it
?Evaluating Freud's theory of dreaming. Is each point a strength or a weakness?
Tap a statement, then tap the group it belongs in. Then press Check.
Mission check
?Freud thought every dream is a disguised wish. Disguised from whom?
From you. Freud said the wish is repressed because your conscious mind would find it disturbing, so dreamwork disguises the latent content as a harmless-looking manifest story. That way the wish is fulfilled without waking you: the dream guards your sleep.
Mission 5
Brain busy, body paralysed: why does REM sleep turn into a story?
Make a guess: Brain busy, body paralysed: why does REM sleep turn into a story?
Sleep and dreaming · activation-synthesis
The brain in REM sleep
In REM sleep brain activity is close to waking levels, the eyes move rapidly and most vivid dreams happen.
Hobson and McCarley (1977) proposed the activation-synthesis theory: dreams are a by-product of brain activity in REM sleep.
Dreams have no hidden message. They come from the brain trying to make sense of its own activity.
Sleep and dreaming · activation-synthesis
Activation
In REM sleep three things happen at once:
Random activation: neurons in the brain stem fire randomly, sending signals up to the higher brain.
Sensory blockade: sensory signals are blocked.
Movement inhibition: signals to the muscles are blocked, so the body is paralysed and can't act out the dream.
Sleep and dreaming · activation-synthesis
Synthesis
The cerebral cortex receives the random signals and tries to make sense of them.
It synthesises them, combining them with stored memories into a story: the dream.
Because the input is random, dreams are often bizarre: sudden scene changes, impossible events, odd mixtures of people.
Any meaning is added by the cortex as it builds the story, not hidden in advance.
Quick check
?Leo dreams that a dog is chasing him, but his legs won't move however hard he tries. Which part of the theory best explains why he can't move?
Sort it
?Evaluating activation-synthesis. Is each point a strength or a weakness?
Tap a statement, then tap the group it belongs in. Then press Check.
Quick check
?Which statement shows the main difference between activation-synthesis and Freud's theory?
Mission check
?Brain busy, body paralysed: why does REM sleep turn into a story?
In REM sleep, neurons in the brain stem fire randomly while the senses are blocked and the muscles are paralysed. The cerebral cortex tries to make sense of this random activity by combining it with stored memories, and the story it builds is the dream, often bizarre because its input was random.
Recap
Big ideas
Sleep keeps the brain healthy, repairs the body and supports emotional stability.
The four sleep stages run from light (stage 1) to deep (stage 4); REM sleep follows, with fast brain activity, paralysed muscles and most dreaming.
Key question: why do you need to sleep and dream? Sleep repairs the body and brain, and dreaming happens mostly in REM.
A cycle lasts about 90 minutes and repeats 4 to 5 times a night, with more deep sleep early and more REM later.
The sleep–wake cycle is a circadian rhythm of about 24 hours; the 90-minute sleep cycle is an ultradian rhythm.
The pineal gland releases melatonin as it gets dark, making you sleepy; levels are high at night and low in the morning.
Light is the main external influence (zeitgeber); Siffre (1975) showed that without zeitgebers the sleep–wake cycle drifts away from 24 hours.
Insomnia means regularly having trouble getting to sleep or staying asleep, with tiredness during the day.
Stress (through the sympathetic nervous system), the bedroom, lifestyle and health can all cause it, often together.
Narcolepsy is a rare brain disorder with daytime sleepiness, sleep attacks and cataplexy, linked to low hypocretin.
Key question: why do you need to sleep and dream? When sleep goes wrong, as in insomnia and narcolepsy, daily life suffers.
Freud: dreams fulfil repressed wishes from the unconscious, disguised by dreamwork so they don't wake you.
Manifest content is the remembered story; latent content is the hidden wish that dream analysis tries to uncover.
Freud (1909) used Little Hans's fantasies to support his theory; weaknesses include bias and a theory that can't be tested.
Key question: why do you need to sleep and dream? For Freud, dreaming lets hidden wishes be expressed safely in disguise.
Activation-synthesis (Hobson and McCarley, 1977): in REM sleep, random activation from the brain stem, sensory blockade and movement inhibition happen together.
The cortex synthesises the random signals with memories into a story, which is why dreams are often bizarre.
Strengths: biological, testable evidence; weaknesses: it ignores meaning and struggles with NREM and lucid dreams.
Key question: why do you need to sleep and dream? For activation-synthesis, dreams are the brain making sense of its own activity during REM.
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Mini-lesson complete!
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You've worked through Sleep and Dreaming for Edexcel GCSE Psychology (1PS0). 🎉
Mission 1You dream mostly in one stage of sleep. What are the others for?
Mission 2Long flight: your body says 3 a.m. at breakfast. What resets it?
Mission 3Lying awake at 3 a.m.: is it the body, the bedroom or the brain?
Mission 4Freud thought every dream is a disguised wish. Disguised from whom?
Mission 5Brain busy, body paralysed: why does REM sleep turn into a story?