5 stages span 90 minutes - each stage have different level of brainwave activity monitored with EEGs
stage 1 & 2
light sleep - easily woken
waves in light sleep/stage 1 & 2
alpha (slower and rhythmic)
theta (slower and deeper)
stage 3 & 4
deep sleep - difficult to wake someone
waves in deep sleep/stage 3 & 4
delta (greater amplitude and slow wave)
stage 5
REM (rapid eye movement) sleep - paralysed body
sped up brain activity
jerky eyelid movement and dreaming
resembles awake brain
AO3 strength - supporting evidence
Dement & Kleitman 1957 = EEG record brain activity in 9 Ps in sleep lab, caffeine and alcohol effects
REM activity correlated with dreaming due to accurate recall when woken up; CA - small sample size therefore low population validity; REB - similar findings in replicated studies
therefore REM sleep important component of ultradian sleep cycle and is accompanied by dreaming
AO3 limitation - methodology
Dement & Kleitman's et al. sleep lab has control of TVs but lacks mundane realism because the participants were attached to machinery which doesn't reflect how they normally sleep - therefore the sleep patterns don't represent their ordinary ones.
