AO3: Zeitgebers

• Limitation: Environmental observations

  What? Don't have same effect in all environments

  Who? Arctic circle - similar sleep patterns all year round despite having six months of total darkness

  Why? Sleep/wake controlled primarily by endogenous pacemakers
• Limitation: Case study evidence

  What? Evidence challenging zeitgebers

  Who? Miles et al. - despite social cues, sleep/wake cycle couldn't be adjusted because of abnormal circadian rhythm

  Why? Social cues alone not effective