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Psychology Revision ­ Unit 3 Sleep

Biological rhythms (changes in the way biological systems behaviour e.g. sleep wake cycle):
The circadian rhythm:
Key Facts:
Circadian Rhythms last about 24 hours ­ e.g. sleep wake cycle and body temperature.
The Suprachiasmitic Nucleus (SCN) is a small group of cells in…

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Research methodology: In all the early studies participants were isolated from variables
which effect there circadian rhythm such as clocks, radio and daylight. However they weren't
isolated from light, as there was an artificial light, which was suggested to not affect the
circadian rhythm, but recent research suggests this isn't…

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A02: The biological approach
All studies here propose that behaviour can be explained in terms of structures in the brain
and hormones however human behaviour is often more complex than this. People do also
make choices about what they do which isn't determined by their biology.
Miles et al (1977)…

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Infradian Rhythms (period of more than one day but less than one year):
Monthly Cycles: Driven by fluctuating hormones which regulate ovulation.
Process: pituitary gland releases hormones (FSH ­follicle stimulating hormone and LH ­
luteinising hormone) which stimulate a follicle in one ovary to ripen an egg and trigger the…

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Born et al (1999): people who were told to wake up at earlier times of the night than usual had
higher levels of ACTH the stress hormone to help them wake up earlier.

Real world application:
Therapies such as phototherapy uses very strong lights in the evening and/or early morning…

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Exogenous Zeitgebers:
Resetting the biological clock with exogenous zeitgebers is known as entrainment.
Free-running is where the biological clock operates in the absence of any exogenous cues.
This is the dominant zeitgeber in humans as it can reset the body's main pacemaker, SCN. It
can also reset oscillators located…

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The power of artificial lighting:
Because light is the dominant zeitgeber, will any level of light work as a zeitgeber?
Siffre, Aschoff and Wevers studies of biological rhythms allowed all pps to be exposed to
artificial lighting as they didn't think it would affect circadian rhythms. However Campbell and

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Jet lad: people report less difficulty in adjusting when they fly west ­ phase delay ­ like going
to bed later than usual (E.g. London to new york) then when flying east ­ phase advance ­
like having to get up earlier than usual (New York to London).

Consequences of…

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Other factors:
Shift work effects: may not just be due to the disruption of biological rhythms. May be due
to the lack of sleep associated with having to go to bed at unusal times.
Shift workers also experience social disruption as well as disruption to there biological
rhythms. (difficult to…

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Lab experiments: Boivin et al is a lab experiment so although extrenous variables can be
carefully controlled it is hard to tell if this research will apply to everyday life. Therefore field
experiments must also be conducted to confirm the findings.
Boivin and James (2002): conducted this experiment in a…


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