Why do we sleep and dream, and what happens when sleep goes wrong?
Sleep, dreams and sleep disorders: the nature and stages of sleep, theories and explanations of why we sleep and dream, sleep disorders, and the research evidence and methods used to study sleep.
The SQA Higher Psychology mandatory Individual Behaviour topic on sleep and dreams: the stages and cycle of sleep, restoration and evolutionary theories of sleep, theories of dreaming, common sleep disorders, and the research evidence and methods used to study them.
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What this dot point is asking
This is the mandatory Individual Behaviour topic, so every candidate is examined on it. The SQA wants you to describe the nature and stages of sleep, explain at least one theory of why we sleep and one theory of why we dream, describe sleep disorders, and use research evidence and methods to support and evaluate these explanations. It is the source of a full -mark question on the Higher paper.
The answer
The nature and stages of sleep
Sleep is studied with the electroencephalogram (EEG), which records brain waves. Wakeful relaxation shows alpha waves, light sleep shows theta waves, and deep slow-wave sleep shows large, slow delta waves. REM sleep shows fast, awake-like brain activity alongside rapid eye movements and near-total muscle paralysis. The whole cycle is governed by the circadian rhythm (the roughly -hour body clock) set by light and managed by the hypothalamus and the hormone melatonin.
Theories of why we sleep
These theories are complementary rather than rivals: restoration explains the bodily function of sleep, while the evolutionary account explains why a need for it was selected for in the first place.
Theories of why we dream
Sleep disorders
Examples in context
Sleep-deprivation research is the most-used evidence on this topic. Studies in which volunteers are kept awake show falling concentration, irritability and microsleeps, supporting the idea that sleep performs a necessary recovery function. The famous case of Randy Gardner, who stayed awake for around days as a teenager, is used on both sides: he showed cognitive and mood problems while deprived, which supports restoration, yet recovered fully afterwards, which a strict restoration account struggles to explain. Animal evidence is used for the evolutionary theory: prey species that must stay alert sleep in short bursts, while safer species sleep longer, fitting the survival-value argument. A Higher answer that pairs a clear theory with two or three of these studies, then judges how well they fit, reaches the top band.
Try this
Q1. Describe the difference between slow-wave sleep and REM sleep. [4 marks]
- Cue. Slow-wave sleep is deep NREM sleep with large delta waves and physical recovery; REM sleep has fast, awake-like brain activity, rapid eye movements, muscle paralysis and vivid dreaming.
Q2. Explain one psychological and one biological theory of dreaming. [8 marks]
- Cue. Psychological: Freud's wish-fulfilment, dreams as disguised unconscious desire with manifest and latent content. Biological: activation-synthesis, the brain making a story from random REM signals.
Exam-style practice questions
Practice questions written in the style of SQA exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
SQA Higher (mandatory)20 marksExplain one theory of why we sleep and evaluate the research evidence that supports it.Show worked answer →
A typical -mark mandatory question, marked for both knowledge and understanding (KU) and analysis or evaluation. Roughly to marks reward accurate description of a theory, such as the restoration theory (sleep restores the body and brain, with slow-wave sleep linked to physical repair and growth hormone release, and REM sleep linked to restoring brain function and memory).
The remaining marks reward use and evaluation of evidence. Strong answers cite studies such as Oswald's work linking sleep to recovery, and the effects of sleep deprivation, then weigh them: deprivation studies support a recovery role, but Randy Gardner stayed awake for days with limited lasting harm, which challenges a purely restorative account. A reasoned judgement on how well the evidence supports the theory is the discriminator.
SQA Higher (mandatory)8 marksDescribe the stages of sleep and the sleep cycle.Show worked answer →
An -mark KU question. Markers want an accurate, ordered description rather than a list of labels.
Sleep moves through stages of non-REM sleep (NREM) from light sleep (stage 1) into deeper slow-wave sleep (stages 3 and 4), then into REM sleep where the brain is active and most vivid dreaming occurs. A full cycle lasts roughly minutes and repeats through the night, with more slow-wave sleep early on and longer REM periods towards morning. Reference to EEG patterns (alpha, theta, delta waves) and to physiological signs such as rapid eye movements and muscle paralysis in REM raises the mark.
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