A03

• A limitation of SCN research is that it may overlook the importance of other body clocks.

  e.g, research has shown that there are many circadian rhythms (peripheral oscillators) in many organs and cells in the body that are influenced by the SCN and can act independently.

  This means that researchers were able to change the feeding patterns of mice and alter the circadian rhythms of the liver by 12 hours, whilst leaving the SCN rhythm unaffected.

  Therefore, => the sleep/wake cycle isn’t solely governed by the SCN and there are other complex influences affecting our circadian rhythms.
• Point: A further limitation is that endogenous pacemakers cannot be studied in isolation.

  Evidence: For example, Siffre’s research managed to isolate endogenous pacemakers in a cave, but such studies are very rare.

  Explain: It is hard to separate pacemakers and zeitgebers for research purposes to study their unique role as they interact in everyday life.

  Link: Therefore, this suggests the more researchers attempt to isolate the influence of internal pacemakers, the lower the validity of the research.
• Point: A limitation of exogenous zeitgebers is that they do not have the same effect in all environments.

  Evidence: For example, some people live in places with very little darkness in summer and very little light in winter.

  Explain: The Inuits of Greenland show to have similar sleep patterns all year round, despite spending around half a year in total darkness.

  Link: Therefore, this seems to suggest that our sleep/wake cycle is predominantly controlled by endogenous pacemakers which can override environmental changes in light.
• Point: A strength of exogenous zeitgebers research is that it could explain age-related insomnia

  Evidence: For example, Hood (2004) found that the management of insomnia was improved if elderly people were more active and were exposed to more natural light by going out during the day.

  Explain: This means changes in lifestyle may be just as likely to cause age-related insomnia as internal biological changes.

  Link: Therefore, this is beneficial as the research can be used to help manage some sleep-related disorders.