strengths

• • The use of carefully controlled conditions and removal of the SCN means that this study has good internal validity
  • The researcher was able to directly observe the effect of circadian rhythm disruption in a way which would have been impossible with human research
• Further support for the influence of endogenous pacemakers on circadian rhythms was provided by Skene & Arendt (2007)
• • They pointed out that most blind people who still have some light perception have normal circadian rhythms of 24 hours, whereas blind people with no light perception display irregular circadian rhythms
  • This demonstrates the importance of light in terms of the internal sleep-wake cycle