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Biological Rhythms & Sleep
The Circadian Rhythm

The Sleep Wake Cycle
o Guided by external cues; knowing the time of day and feeling tired when it gets dark. The
endogenous clock works without cues, setting the cycle for 24-25 hours. External cues
(E.g. daylight) help to adjust the internal clock…

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(1983) tested cognitive performance in a field rather than a lab situation and didn't find any

Ultradian & Infradian Rhythms

Ultradian Rhythms
o Sleep Stages
Stages 1 + 2 ­The brain produce a typical pattern called a BETA wave. As you
become more relaxed, your waves become more slow…

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Two weeks after ovulation, if there is no pregnancy, progesterone is reduced and
this caused the lining of the womb to be shed.


1. Exogenous Cues ­ Research has shown that women who live together (and do not take
contraceptives) tend to menstruate at the same time every month.…

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Murphy (1998) found that if you shine a light on the back of pp's knees, it shifts their
circadian rhythm.
o Social Cues ­ Biologists believe that social cues were the main zietgebers for human
circadian rhythms. Our daily rhythm appeared to be entrained by social convention, not
internal biology.…

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1. Sleep Patterns ­ Sleep is an adaptive mechanism that makes their parents lives easier.
Daytime sleep allows parents to carry out chores ­ enhancing survival. Night waking ensures
that the bay is fed regularly, forcing the parent to acknowledge their cold and hungry state.
2. REM Sleep ­ An…

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3. Reduced Sleep ­ This is partly due to physiological changes as well as actual problems staying
asleep. Problems staying asleep are also explained by the fact that deep sleep is reduced in
old age.
4. Explanation of Old Age ­ Reduction in SWS leads to a reduced production of…

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The Nature of Deindividuation
o Characteristics ­ Low self-evaluation and decreased concern about the evaluation of
others. This leads to an increase in behaviour that is not normally inhibited by social
o Factors ­ Anonymity and altered consciousness due to drugs or alcohol. Zimbardo (1969)
stressed that…

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2. Lack of Support ­ A meta-analysis of 60 studies concluded that there is insufficient support
for this theory. Postmes and Spears (1998) found that disinhibition and antisocial behaviour
are not more common in large groups and anonymous settings. Neither was there much
evidence relating to reduced self-awareness.
3. Pro-social…

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model however, is criticised by Poole and Regoli, as they found that the best indicator of
violence among juvenile offenders was pre-institutional violence.

o Stages in the process
Difficult social conditions
= Scapegoating of less powerful group
= Negative evalution and dehumanisation of target group
= Moral values and…

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tryptophan exhibited increased aggressive behaviour, suggesting a link between serotonin
and aggression. Popova et al. suggested that in animals, they are selectively bred for
domestication and for increasingly docile temperaments ­ there is an increasing
concentration of serotonin.
2. Evidence from Antidepressants ­ Low levels of serotonin are associated with…


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