Ultradian Rhythms

• What is the definition of an ultradian rhythm?

  A cycle that lasts less than 24 hours
• What is one of the most intensively researched ultradian rhythms?

  The stages of sleep
• How many distinct stages of sleep have psychologists identified?

  Five distinct stages of sleep
• How long does a complete sleep cycle last?

  90 minutes
• What characterizes each stage of sleep?

  Different levels of brainwave activity
• What are the two main types of sleep stages?

  REM and NREM sleep
• What is the duration of Stage 1 of sleep?

  10 minutes
• What brainwave activity is associated with Stage 1 sleep?

  Alpha waves
• How long does Stage 2 of sleep last?

  20 minutes
• What brainwave patterns are observed in Stage 2 sleep?

  Sleep spindles and K complexes
• What characterizes Stages 3 and 4 of sleep?

  Slow delta waves with greater amplitude
• How long do Stages 3 and 4 of sleep last?

  20-40 minutes
• What is the characteristic of Stage 5 sleep?

  Body paralyzed with full REM sleep
• How long after sleep onset does Stage 5 occur?

  90 minutes
• What does evidence suggest about the stages of sleep?

  There are distinct stages in sleep
• What did Dement and Kleitman (1957) find about REM sleep?

  REM activity correlates with dreaming
• What was a criticism of Dement and Kleitman's study?

  The small size of the original sample
• What is a gender bias in ultradian sleep cycle research?

  Use of an all male sample
• What did Tucker et al. (2007) find about individual differences in sleep cycles?

  Significant differences in stage duration
• Why is gender bias a weakness in sleep research?

  It may not represent female sleep patterns
• What does lucid dreaming suggest about sleep stages?

  Some skip stages and go to REM
• What is a methodological issue in sleep research?

  Artificial sleep environment in labs
• Why does the artificial nature of sleep research matter?

  It lacks ecological validity
• What are the stages of sleep and their characteristics?

  • Stage 1: Light sleep, 10 minutes, Alpha waves
  • Stage 2: Non-REM, 20 minutes, Theta waves, Sleep spindles
  • Stage 3: Deep sleep, Slow delta waves, 20-40 minutes
  • Stage 4: Deep sleep, Greater amplitude, 20-40 minutes
  • Stage 5: REM sleep, Body paralyzed, 90 minutes after sleep onset
• What are the strengths and weaknesses of the research on ultradian sleep cycles?

  Strengths:

  • Evidence supports distinct sleep stages
  • Correlation between REM and dreaming

  
  

  Weaknesses:

  • Gender bias in samples
  • Individual differences in sleep patterns
  • Methodological issues with artificial environments