A03

• What are the strengths of circadian rhythms?

  1. Practical application to shift work
  2. Practical application to drug treatments
• What are the limitations of circadian rhythms?

  1. Poor control in studies
  2. Use of case studies and small samples
  3. Individual differences
• Strength = practical application to shift work

  • Knowledge of circadian rhythms has given us a better understanding of the adverse consequences if they are disrupted
  • e.g. Boivin et a. (1966) - night workers engaging in shift work experience a period of reduced concentration around 6 am resulting in more mistakes and accidents
  • e.g. Knutsson (2003) - a relationship found between shift work and poor health - shift workers are 3x more likely to develop heart disease
  • May have economic implications of how to best manage worker productivity
• Strength = practical application to drug treatments

  • Chronotherapeutics - the study of how timings affects drug treatments
  • There are certain peak times during the day or night when drugs are likely to be at their most effective
  • Has led to the development of guidelines to do with the timing of drug dosing for a whole range of medications e.g. anticancer, anti-epileptic etc.
• Limitation = poor control in studies

  • In most early research studies of circadian rhythms participants were isolated from variables that might affect their circadian rhythm, such as clocks, radios etc.
  • But they were not isolated from artificial light as it was believed artificial light wouldn't affect their circadian rhythms
  • Researcher suggests this may not be true - participants' circadian rhythms down to 22 hours and up to 28 hours using dim artificial lighting alone
  • Early studies may have been confounded by artificial light
• Limitation = use of case studies and small samples

  • Studies of the sleep/ wake cycle tend to involve small groups or studies of single individuals
  • May not be representative of wider population
  • In Siffre's most recent cave study he observed, at the age of 60, that his interna clock ticked much more slowly than when he was a young man
  • Illustrates that even when the same person is involved there are factors that vary which may prevent general conclusions being drawn
• Limitation = Individual differences

  • Cycle length: research has found that circadian cycles can vary from 13 to 65 hours
  • Cycle onset: Individuals appear to be innately different in terms of when their circadian rhythms reach their peak
  • This explains why some people prefer to rise early and go to bed early, whereas others prefer the opposite