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Outline and evaluate restoration explanations of the functions of sleep.
(8 marks + 16 marks)
The restoration explanation to explain sleep proposed by Oswald (1980) suggests there are 2
functions; SWS to enable body repair, and REM to enable brain recovery.
During SWS, a growth hormone (GH) from the pituitary gland is released so protein synthesis which
allows for cell growth to take place. This restores body tissue which is important because proteins
are fragile and must be constantly replaced, making SWS a part of the body's natural recovery
Sassin found that when sleep cycles are reduced by 12 hours, the release of the GH is also reversed,
which proves how the release of the GH is linked with neural mechanisms to SWS.
Sassin's findings are supported by research by Van Cauter and Plat (1996) who found that the
amount of GH released correlates with the amount of SWS. They also found that the decline of GH in
elderly people has also been associated with reduced SWS.
This therefore gives academic credibility and reliability to Sassin's research because it is high in
ecological validity which gives us a good idea of the correlation between GH release during SWS.
To test whether SWS has an important restorative effect, there have been studies undergoing sleep
deprivation to see the effects on the body.
Studies have been carried out on non-humans which show that total sleep deprivation has fatal
consequences. Rechstaffen et al forced rats to remain physically active by rotating a disk they were
on every time they fell asleep. After 33 days, all sleep-deprived rats which suggests that a total lack
of SWS after a while breaks down the body and kills a person.
On the other hand, there are ethical issues with Rechstaffen's study because animals endured
torturous lives for an entire month and were inevitably killed. It's possible that the research did not
serve any scientific purpose because a rat's physiology is completely different to that of a human and
can't be generalised.
Furthermore, it's possible that the rats died from stress instead, because Rattenborg carried out the
same study on pigeons without any ill effects, suggesting that Rechstaffen's study is low in internal
validity because it was not SWS deprivation measured, but something such as stress instead.
Overall, there are issues with human research into sleep deprivation because the samples have been
generally restricted to case studies or observational studies of small groups of participants.
Most studies thereby lack population validity because participants in sleep deprivation studies are
likely to be of a certain personality type. For instance, someone who has difficulty sleeping is less
likely to volunteer for studies of sleep deprivation, and those who do volunteer are probably more
motivated to try and cope well with sleep deprivation, therefore research lacks population validity
because it's not representative of everybody.
Alternatively, REM sleep has been associated with brain growth. During lifespan changes, babies
have much higher REM percentages to cope with their rapid brain growth. The restoration
explanation suggests that the amount of REM sleep in any species is proportional to the immaturity
of the offspring at birth; for example the platypus is immature at birth and has about 8 hours of REM
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REM from birth.
This suggests a relationship between neural development and REM sleep.
Studies to investigate REM functions have tested the effects of partial sleep deprivation, known as
`REM rebound' which is the need for more sleep after a night deprived of REM sleep. To achieve REM
sleep deprivation, researchers wake sleeping volunteers as soon as their eyes start to move.…read more