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A2 PSYCHOLOGY NOTES Biological Rhythms, Sleep and Dreaming
RESTORATION THEORY OF SLEEP
The restoration theory of sleep suggests that during the day, wear and tear on our bodily tissues and
organs leads to damage, then at night during sleep, the body repairs these damaged tissues and cells
(Adam & Oswald, 1983). Evidence from empirical research, however, suggests that only nonREM sleep
is involved in restoring the body. According to Hartmann (1973), there is an increase in the amount of
time devoted to REM sleep following periods of intense exercise and this has been demonstrated in
several species of animal.
In humans, stage 4 sleep seems to be particularly important for repairing damage: Shapiro (1981)
investigated the sleep of Ultramarathon runners before and after they took part in a competition
(Ultramarathons are 57 miles). For the two days following the competition they slept 1½ hours longer.
Stage 4 sleep was 45% of total sleep time rather than the usual 25%.
Further evidence for the role of stage 4 sleep comes from observations that a growth hormone that is
important for RNA and protein synthesis, and hence tissue growth is released during stage 4 sleep.
Also, when stage 4 sleep is prevented (by waking up participants whenever they enter this stage), they
develop symptoms similar to those of fibrositis (severe inflammation of the back muscles). Moreover,
fibrositis sufferers experience a chronic lack of stage 4 sleep.
Other evidence that demonstrates the importance of stage sleep comes from sleep deprivation studies
such as the case of Randy Gardner. While Gardner did sleep for longer after his ordeal (15 hours when
he first fell asleep and longer than usual for a few nights), he only recovered about 25 hours of his sleep
debt before reverting to his normal sleep wake cycle nevertheless this was mostly stage 4 sleep
(recovered 70%) and REM (recovered 50%).
Evidence against restoration theory
In an experiment where healthy participants spent six weeks in bed, Ryback and Lewis (1971) found no
change in their patterns of sleep. Restoration theory, on the other hand, would predict that these
participants would have less sleep, since less damage would occur if they are inactive.