Topic 9: Sleep and dreaming - 9.2 Studies — Edexcel GCSE Psychology
Test yourself on Topic 9: Sleep and dreaming - 9.2 Studies with PEARSON EDEXCEL GCSE practice questions.
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Topic 9: Sleep and dreaming - 9.2 Studies explained
Michel Siffre spent six months in a cave to study the effects of isolation on the sleep-wake cycle, without external time cues like daylight or clocks.
Read the full explanation
He found that his circadian rhythm extended from a 24-hour cycle to approximately 25 hours. His perception of time was also distorted; he believed he had been in the cave for a shorter period than he actually had. This demonstrated that the human body has an internal pacemaker (endogenous pacemaker) regulating sleep, but it requires external cues (exogenous zeitgebers) to stay synchronised with the 24-hour day. As a case study of one man, it lacks generalisability, and Siffre experienced severe physical and psychological deterioration during the isolation.
Your focus
- Describe the aims, procedures, and findings of Siffre's (1975) cave study.
- Explain the role of endogenous pacemakers and exogenous zeitgebers in the sleep-wake cycle.
- Evaluate the strengths and weaknesses of Siffre's study, including methodological and ethical issues.
Topic 9: Sleep and dreaming - 9.2 Studies exam tips
Marking Points
- Identify the aim: to investigate the natural sleep-wake cycle without external time cues.
- Describe the method: a six-month case study in a cave without natural light or clocks.
- State the findings: his sleep-wake cycle extended to around 25 hours, and time perception was distorted.
- Explain the conclusion: endogenous pacemakers control the sleep-wake cycle but need exogenous zeitgebers to maintain a 24-hour rhythm.
- Evaluate the study: strengths include detailed longitudinal data; weaknesses include lack of generalisability and psychological distress.
Examiner Tips
- 💡Use the terms 'endogenous pacemaker' and 'exogenous zeitgeber' accurately when explaining Siffre's conclusions.
- 💡Remember that as a case study of one individual, the findings cannot be easily generalised to the wider population.
- 💡Be prepared to evaluate the ethics of the study, noting the severe psychological and physical toll the isolation took on Siffre.
Common Mistakes
- Believing Siffre's sleep cycle shortened. Correction: His sleep-wake cycle actually lengthened to around 25 hours.
- Thinking Siffre had no light at all. Correction: He had artificial light, which may have acted as a confounding variable affecting his circadian rhythm.
- Confusing endogenous and exogenous factors. Correction: Endogenous pacemakers are internal biological clocks, whereas exogenous zeitgebers are external environmental cues like sunlight.