circadian rhythms

circadian rhythms are biological cycles lasting around 24 hours. e.g sleep/wake cycle or body temperature

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Aschoff and Weber
placed participants in a bunker with no natural light. They settled into a sleep/wake cycle of between 25 and 27 hours, suggesting that endogenous pacemakers control the sleep/wake cycle in the absence of light cues.
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Siffre
spent 6 months in a cave with no time cues. artificial lights came on when he was awake. he settled into a sleep/wake cycle of 25 to 30 hours. supports the idea that endogenous pacemakers exert and influence on circadian rhythms
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Folkard et al
Isolated 12 participants from natural light for 3 weeks, manipulating the clock so that only 22 hours passed a day. of the 12 participants 11 kept pace with the clock. this shows the strength of the circadian rhythm as a free-running cycle
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Czeisler
kept 24 participants in constant artificial low-level light for one month and put them on a 28 hour cycle. When readings of body temperature and blood chemicals were analysed they were shown to have adopted a cycle of 24 hours and 11 minutes.
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Duffy et al
found that early risers prefer 6am to 10pm and later risers prefer 10am to 1am. this shows that individual differences exist in sleep/wake cycles
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Card 2

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spent 6 months in a cave with no time cues. artificial lights came on when he was awake. he settled into a sleep/wake cycle of 25 to 30 hours. supports the idea that endogenous pacemakers exert and influence on circadian rhythms

Back

Siffre

Card 3

Front

Isolated 12 participants from natural light for 3 weeks, manipulating the clock so that only 22 hours passed a day. of the 12 participants 11 kept pace with the clock. this shows the strength of the circadian rhythm as a free-running cycle

Back

Preview of the back of card 3

Card 4

Front

kept 24 participants in constant artificial low-level light for one month and put them on a 28 hour cycle. When readings of body temperature and blood chemicals were analysed they were shown to have adopted a cycle of 24 hours and 11 minutes.

Back

Preview of the back of card 4

Card 5

Front

found that early risers prefer 6am to 10pm and later risers prefer 10am to 1am. this shows that individual differences exist in sleep/wake cycles

Back

Preview of the back of card 5

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