Understanding Psychology (10th Ed)

rapid eye movement (REM) sleep
Sleep occupying 20% of an adult’s 
sleeping time, characterized by 
increased heart rate, blood pressure, 
and breathing rate; erections; eye 
movements; and the experience of 
dreaming.
FIGURE 3 
During the night, the typical 
sleeper passes through all four stages of 
sleep and several REM periods. 
(Source: 
From Ernest Hartmann, 
The Biology of 
Dreaming
(1967), p. 6. Courtesy of Charles C 
Thomas Publisher, Ltd., Springfi eld, Illinois.)
REM sleep 
1 
Sleep stage 
0 1 
Hours slept 
3 8 
5 
2 4 6 
7 
4 
3 
2 
Wakefulness
People progress through four distinct stages of sleep during a night’s rest spread over cycles 
lasting about 90 minutes. REM sleep, which occupies only 20% of adults’ sleeping time, occurs 
in stage 1 sleep. These photos, taken at diff erent times of night, show the synchronized 
patterns of a couple accustomed to sleeping in the same bed.
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Paradoxically, while all this activity is occurring, the major muscles of the body 
appear to be paralyzed. In addition, and most important, REM sleep is usually accom-
panied by dreams, which—whether or not people remember them—are experienced 
by everyone during some part of their night’s sleep. Although some dreaming occurs 
in non-REM stages of sleep, dreams are most likely to occur in the REM period, where 
they are the most vivid and easily remembered (Conduit, Crewther, & Coleman, 2004; 
Lu et al., 2006; Titone, 2002). 
There is good reason to believe that REM sleep plays a critical role in everyday 
human functioning. People deprived of REM sleep—by being awakened every time 
they begin to display the physiological signs of that stage—show a rebound effect
when allowed to rest undisturbed. With this rebound effect, REM-deprived sleepers 
spend signifi cantly more time in REM sleep than they normally would. In addition, 
REM sleep may play a role in learning and memory, allowing us to rethink and 
restore information and emotional experiences that we’ve had during the day 
(Nishida et al., 2009; Walker & van der Helm, 2009). (Also see Applying Psychology in 
the 21st Century .)
Study Alert
Diff erentiate the fi ve stages 
of sleep (stage 1, stage 2, 
stage 3, stage 4, and REM 
sleep), which produce dif-
ferent brain-wave patterns.