A01

• What does the German word zeitgeber mean?

  'Time giver'
• What are exogenous zeitgebers?

  External factors that reset biological clocks
• What process do exogenous zeitgebers use to reset biological clocks?

  Entrainment
• What happens to the free-running biological clock in the absence of external cues?

  It continues in a distinct cyclical pattern
• What study is referenced regarding the free-running cycle?

  The Siffre study
• How does light function as a zeitgeber in humans?

  It resets the SCN and maintains sleep/wake cycle
• What indirect influences does light have on the body?

  It affects hormone secretion and blood circulation
• Who conducted the innovative study on light detection?

  Scott Campbell and Patricia Murphy
• What was the main finding of Campbell and Murphy's study?

  Light can be detected by skin receptors
• How much deviation in the sleep/wake cycle was produced in participants?

  Up to three hours
• What does the study suggest about light as a zeitgeber?

  It is a powerful exogenous zeitgeber
• How do newborn babies' sleep/wake cycles compare to adults?

  They are initially random and not synchronized
• At what age do circadian rhythms begin in babies?

  About 6 weeks of age
• When are babies' rhythms typically entrained by parental schedules?

  By about 16 weeks
• What factors imposed by parents help entrain babies' rhythms?

  Mealtimes and bedtimes
• What does research on jet lag suggest about entraining circadian rhythms?

  Adapting to local eating and sleeping times helps
• What is the effect of responding to one's own feelings of hunger and fatigue when traveling?

  It is less effective for entraining rhythms