Biological Rhythms

• Supporting evidence for ultradian rhythms

  Dement & Kleitman (1957)- found that a consistency of timings of sleep-stage cycle between all ppts suggests the sleep stage cycle is controlled by endogenous pacemakers.

  A large different would suggest that exogenous factors are responsible as they are unique.
• Supporting evidence for infradian rhythms

  Stern & McClintock (1998)- demonstrated how exogenous factors such as pheromones can influence a woman's infradian menstrual cycle.
• Supporting evidence for circadian rhythms

  Kleitman & Richardson (1938)- found that without light, biological rhythms continue but become very inconsistent. Suggesting that sunlight acts as an exogenous zeitgeber.
• However point for Kleitman & Richardson

  They had access to food and social interactions (exogenous zeitgebers). This means that endogenous pacemakers may not have solely controlled their body clock.
• Supporting evidence for circadian rhythms

  Vetter et al (2011)- found that when ppts were exposed to warm light their rhythm synced with dawn and when exposed to blue light their rhythm synced with work hours. They concluded that light type affects the SCN and the sleep/wake cycle.
• What is a limitation of sleep studies regarding sample size?

  They often involve small number of participants
• Why can't generalizations always be made from sleep studies?

  Due to small sample sizes
• What are the two types of individuals based on sleep patterns?

  'Larks' and 'owls'
• How does age influence the sleep/wake cycle?

  Adolescents' rhythms run 2 hours later than adults
• What were the ages of Richardson and Kleitman during their experiments?

  Richardson was in his early 20s, Kleitman in his 40s
• What were the implications of the research conducted in North Tyneside regarding school hours?

  • Lessons started at 10am
  • Positive academic outcomes
  • Improved health outcomes
• What negative effects can result from desynchronisation of circadian rhythms?

  Disruption of synchrony between cues and pacemakers
• How do changing shift patterns affect shift workers?

  They are more likely to develop heart disease
• What are some psychological effects of shift work?

  Lowered vigilance and increased anxiety