Rhythms

• What are the 3 types of rhythms?

  1. Circadian
  2. Infradian
  3. Ultradian
• What is the circadian rhythm?

  The internal biological clock that regulates the sleep-wake cycle.
• What is the term for an external factor?

  Exogenous zeitgeber
• What is it called when the biological clock is left without any exogenous zeitgebers (external factors)

  It 'free-runs'
• What is another example of the circadian rhythm besides the sleep-wake cycle?

  Core body temperature
• Who lived in a cave for 6 months to see the effects on his biological rhythms?

  Siffre
• What happened to Siffre in the cave?

  His rhythm slowed down and sometimes stretched up to 48 hours
• What did Siffre's study show about circadian rhythms?

  Biological rhythms heavily rely on exogenous zeitgebers to function
• Who found further contradictory research on circadian rhythms with 12 people in a cave?

  Folkard
• What did Folkard find?

  His PPs could not adjust to a 22 hour sleep cycle when he changed the clock without them knowing
• What are the strengths of circadian rhythms?

  • Real-life application - shift work and knowing the best time to take drugs
  • Research support - Siffre, Folkard
• What are the limitations of circadian rhythms?

  • Genetic differences in people (participant variables)
  • Small samples & case studies used so can't generalise
  • Artificial tasks
  • Not a fully controlled environment (cave)
• What is an infradian rhythm?

  An infradian rhythm is a biological rhythm that occurs over a period longer than 24 hours, such as the menstrual cycle.
• What is an example of another infradian rhythm?

  Seasonal affective disorder - circannual rhythm
• Who studied whether women's period cycles sync when sharing pheromones?

  McClintock
• How did McClintock get the pheromones from women at different stages of their cycles and how were they transferred to the other women?

  The women placed a cotton pad in their armpit for 8 hours and they were later rubbed on the lips of the women each day
• What were the findings of McClintock's study?

  The women had been brought closer to their 'odour donor'
• What are the strengths of infradian rhythms?

  • Real-life application for treating disorders (seasonal depression)
  • Evidence of exogenous zeitgebers
• What are the limitations of infradian rhythms?

  • Research is unreliable - results haven't been repeated
  • Sample issue with McClintock
  • McClintock's study could be coincidental
• What are ultradian rhythms?

  Ultradian rhythms are biological rhythms that occur more than once a day, with a period shorter than 24 hours.
• What is an example of an ultradian rhythm?

  The sleep cycle
• How do they study brain activity during the sleep cycle?

  They use EEG to observe electrical impulses
• How many stages are there in the sleep cycle?

  5
• How long do the sleep stages last in total?

  Around 90 minutes
• What are the strengths of ultradian rhythms?

  • Scientific methods used - EEG is an objective method
  • EEG can become more accurate using ERP
• What are the limitations of ultradian rhythms?

  • Participant variables - different sleep cycles
  • EEG studies are artificial
• What happens in each stage of the sleep cycle?

  • Stage 1&2 - deeper brainwaves
  • Stage 3&4 - larger brainwaves and deeper sleep
  • Stage 5 - REM sleep, brain activity speeds up