Nature of Sleep

• 5 stages of sleep
• 5 cycles (each of 90 mins.)

• Sleep consists of REM and NREM sleep

NREM sleep consists of 4 stages

Stages 1-2

- Alpha and theta waves

- Heart rate slows and temperature drops

-Easily awoken

Stages 3-4

- Slow delta waves

- Most of the bodies repair work is undertaken + production of growth hormones

• REM sleep- activity resembles the awake brain.

- Paradoxical sleep as the brain and eyes are active but the body is paralysed.

Research evidence for the stages of sleep.

Dement & Kleitman

Conducted a study using 9 participants

For up to 61 nights in a lab.

They woke participants at different stages of sleep.

80-90% recalled dreams when woken during REM sleep.

Only 7% reported dreams when woken in NREM sleep.

Research has stood the test of time and provides strong empirical evidence for the stages of sleep.

Contradictory Research

Some studies- 70% of participants reported dreams during NREM sleep.

Foulkes attributed this difference to confusion over what constitutes a dream.

Muddled thoughts or vague dream like experiences have been incorrectly categorised as dreams.

This is a difficulty in studying dreams.

Although sleep stages are based on empirical scientific evidence that can be measured objectively, dreams are subjective and rely on retrospective data.

Therefore cannot be measured objectively.

Population Validity

Lack of research into sleep in the middle aged.

Dement believes this is because they are too busy raising a family or working to volunteer for sleep studies.

There busy lives mean they are exactly the group that should be researched as it is also the time when many sleep problems occur.

This suggests that our knowledge of sleep is limited due to an inadequate sample of volunteers.