A03

• What is a limitation of exogenous zeitgebers?

  They do not affect all environments equally
• How do the experiences of people in extreme light conditions differ from the usual narrative?

  They maintain similar sleep patterns year-round
• What is the sleep pattern of people living within the Arctic Circle?

  Similar sleep patterns all year round
• What does the experience of Arctic Circle inhabitants suggest about the sleep/wake cycle?

  It is primarily controlled by endogenous pacemakers
• What does case study evidence indicate about exogenous zeitgebers?

  • Evidence challenges their role
  • Laughton Miles et al. (1977) study
  • A blind man had a circadian rhythm of 24.9 hours
  • His sleep/wake cycle couldn't be adjusted by social cues
• What was the circadian rhythm of the blind man studied by Laughton Miles et al.?

  24.9 hours
• What social cues were the blind man exposed to in the study?

  Regular mealtimes
• What conclusion can be drawn from the blind man's inability to adjust his sleep/wake cycle?

  Social cues alone are ineffective for resetting rhythms