Evaluation of Circadian Rhythms

• strengths

  • practical application to shift work
  • practical application to drug treatments (chronotherapeutics)
• practical application to shift work 


  knowledge of circadian rhythms have given us a better understanding of the adverse consequences if they are disrupted- desynchronisation

  • Bolvin et al. (1966)- night workers engaging in shift work experience a period of reduced concentration around 6am resulting in more mistakes and accidents
  • Knutsson (2003)- a relationship found between shift work and poor health- shift workers are three times more likely to develop heart disease

  research into the sleep/wake cycle may have economic implications in terms of how to best manage worker productivity
• practical application to shift work COUNTER ARGUMENT 


  correlational research-> difficult to establish whether desynchronisation of the sleep/wake cycle is actually cause of negative effects. there may be other factors. eg. Solomon (1993)-> high divorce rates in shift workers might be due to missing out on important family events. suggests that it may not be biological factors that create adverse consequences with shift work
• practical application to drug treatments (chronotherapeutics) 


  one real-world application of circadian rhythms is chronotherapeutics- the study of how timing 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 such as anticancer, anti-epileptic etc
• limitations

  • poor control in studies
  • use of case studies and small samples
  • individual differences
• poor control in studies

  • in most early research studies of circadian rhythms ppts. were isolated from variables that might affect their circadian rhythm, such as clocks, radios etc. but they were not isolated from artificial light because it was believed that dim artificial light would not affect their circadian rhythm
  • research suggests that this may not be true- researchers altered ppts' circadian rhythms down to 22 hours and up to 28 hours by using dim artificial lighting alone-> these early studies may have been confounded by the presence of artificial light
• 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 the wider population and this limits the extent to which meaningful generalisations can be made
  • in Siffre's most recent cave study he observed, at the age of 60, that his internal clock ticked much more slowly than when he was a young man. this illustrates the fact that, even when the same person is involved, there are factors that vary which may prevent general conclusions being drawn
• 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 like to rise early and go to bed early, whilst others prefer to wake late and go to bed late