Ultradian Rythms

Question 1

Supporting evidence for ultradian sleep cycles

Answer 1

Supporting evidence for ultradian sleep cycles comes from research conducted by Dement & Kleitman (1957). They studied 9 participants who slept for up to 61 nights in a laboratory whilst their brain activity was recorded using an EEG. They found that activity changed
predictably in sleep cycles throughout an entire sleep period. They woke participants during
different stages of sleep and found that people awakened during REM sleep reported dreams 80-90% of the time, compared to only 7% for NREM sleep. Replications of their research have produced reliable findings and provide strong empirical evidence for the five stages of sleep occurring as part of an ultradian rhythm, However….

Question 2

Research into the stages of sleep links to the debate of psychology as a science.

Answer 2

Research into the stages of sleep links to the debate of psychology as a science. The use of a laboratory setting allows scientists to control conditions to reduce extraneous variables, such as what is consumed before sleep, to isolate the role of biological mechanisms. However, to measure the physiology of sleep in a laboratory, participants are connected to many electrodes, which can affect the quality and quantity of sleep they experience. Therefore, the environment does not reflect the range of factors that can influence sleep in real life and therefore laboratory-based research into sleep lacks ecological validity.

Question 3

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Answer 3

There is often a lack of population validity in sleep-lab research, as volunteer samples of
young people are often used. Middle-aged people may be busy trying to raise families and
succeed at work, so find less time to volunteer for lengthy sleep research. This suggests our
knowledge of the stages of sleep is limited due to the use of unrepresentative samples.