The nature of sleep and lifespan changes, restoration theory and the evoloutionary approach

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Psychology revision part B ­ Sleep States
The nature of sleep and lifespan changes:
The developmental approach: considers human behaviour from a perspective of how it changes
over the course of a person's lifespan. Focuses on averages and how they are different at all ages.
The Nature of Sleep:
What is sleep: it involves being very still except if you're a dolphin. Sleepers are quite
unresponsive and are in an altered state of consciences. We usually sleep in a quiet private
secure place e.g. our bedroom. We can however sleep standing up if we have to; cows and
horses sleep standing up.
The time spent sleeping varies: giraffes sleep for 3 hours whereas sloths sleep for 20 hours.
Characteristic activity of electric in the brain can tell you when you are in the different stages.
REM sleep is absence in reptiles.
Sleeps necessary for survival, species have special patterns adapted to them.
Life Span changes in sleep:
Prenatal sleep: difficult to see sleep patterns, can only see REM sleep.
Premature babies EEG's aren't as valid as they aren't still in the uterus.
Okai: studied REM and NREM sleep in unborn babies of 30 pregnant women, identified at 32
weeks. Correlates with neurone structures responsible for sleep stages: may help explain
brain development.
Infants sleep: about 17-18 hours of sleep a day, 50% is REM and it is only interrupted for
3-4 hours for food. By 6 months babies sleep longer for about 6 hours before they need
food again, tends to be associated with the night time. Can however be influenced by
parents behaviour.
Toddlers: by 12 months children sleep for 13 hours ­ REM sleep for 4-5 hours. Age 2-3
daytime naps are still common. A02: Armitage: babies of depressed mothers took longer to
fall asleep than those of other mothers had more episodes of sleep during the day.
Mechanisms unclear but thought to be linked to maternal hormones and or genetics.
Baird; found that risk of waking at night was associated with depression prior to pregnancy
Childhood: 5-12 years total sleep declines. Younger children straight into SWS before usual
cycle starts and you generally wake up feeling refreshed at this age.
Adolescences: social pressures and reduced parental influence and staying up later
Crowley (2007): sleep patterns vary with school years, Mondays we get jet lag.
Carskadon: A grade 16-18 year olds slept an average of an hour a day extra than others.
[Critical stage of development which is crucial to healthy development.]
Hansen: Suggests school start time should adjust to accommodate for this ­ no tests before
Adults: Sleep time and structure both change. Total sleep decreases and the time it takes to
get to sleep increases. We also at this stage wake up more during the night and begin again
to feel refreshed on waking. Daytime naps also increase.
A02: poor sleep associated with depression, poor memory and greater use of sleep remedies.
Healthy adults much less likely to nap. Anocoli: poor sleep in elderly due to ill health.

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Cultural differences in sleep patterns:
Tanjala et al (1993): surveryed 11-16 year olds from 11 EU countries (over 40,000 children).
Was found that Israeli children slept least ­ in average of about 8.5 hours. And swiss children
slept most on average of about 9.5 hours.
Explanations of sleep:
Restoration Theory:
Slow wave sleep allows the body to repair and REM allows for brain recovery.
Slow wave sleep (SWS):
Growth hormone secreted which is important for childhood growth and development.…read more

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Crick and Mitchison: during REM sleep unwanted memories are discarded and more
important memories are accessible
REM may consolidate procedural memory SWS consolidation of semantic memory and
episodic memory.
[The effects of sleep deprivation ­ look to sheet: however remember case studies here are used
and so participants are likely to be unique and as seen in the biological approach there are many
individual differences when looking into sleep. Ethical issues: depriving people of sleep.…read more

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Zepelin and rechtschaffen (1974): smaller animals with high metabolic rate sleep more than
larger animals
Supports the view that energy conservation is a main reason for sleep.
However, exceptions such as sloths which are very large animals and sleep for 20 hours.
Allison and Cicchette (1976): species who have a higher risk of predatation sleep less,
however expectations such as rabbits sleep as much as those who have a low danger rating.…read more


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