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Biological Rhythms and Sleep,
Aggression & Relationships…read more

Slide 2

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Biological Rhythms and
Circadian rhythms
Infradian rhythms
Ultradian rhythms
Endogenous Pacemakers…read more

Slide 3

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Circadian Rhythm
· 24 hour cycles
· Sleep/wake cycle most known
· Michel Siffre aka `cave man' -> spent 6 months in
cave absent from cues, his rhythm settled to 24
hours but sometimes 48 hours.
· Aschoff & Wever -> pp's in WW2 bunker, isolated
from cues, most rhythms between 22-24 hours
but some as long as 29 hours. Shows that external
cues are important at entraining rhythms.…read more

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· Early research flaw when estimating free running
-> not isolated from artificial light
Cziesler et al altered pp's rhythms from 22 hours to 28
hours using dim lighting.
· Individual differences:
Cycle length -> research has shown that they can vary
from 13 to 65 hours.
Cycle onset -> people have different peak times
Duffy et al, morning people wake up and go to bed
earlier, night people are opposite.
· Positive research evidence to show that exogenous
cues are important in the regulation of rhythms.…read more

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Body Temperature
· Follows 24 hour pattern
· Lowest at 4:30am 36c
· Trough after lunch -> not linked to food intake
· Highest at 6:30pm 38c
Wright et al, proposed higher body temperature leads to
increased physiological arousal and increased cognitive
Hord & Thompson, tested cognitive performance in a
field experiment and found that there was no
Follard et al, learning ability of 12-13 years, 2 groups had
stories read at either 9am or 3pm. Group at 3pm had
superior recall and retained 8% more meaningful
information.…read more

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Ultradian Rhythms
· 90 minute cycle
· BRAC (basic rest activity cycle):
Friedman & Fisher, observed psychiatric patients
over a 6 hour period and found a clear 90 minute
cycle of eating and drinking.
· BRAC ensures that biological processes work in
unison through its strict 90 minute cycle ->
provides nutrients to survive, body has what it
needs to run properly.…read more

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