Psychology Unit 3: Sleep

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Biological Rhythms

Definition: Physiological processes that have a cyclical nature, repeating over a set time, e.g. Circadian rhythms last for around 24 hours, and determined by internal biological mechanisms (endogenous pacemakers)

Circadian Rhythms: 24 hours e.g. sleep-wake and body temperature

Infradian Rhythms: over 24 hours e.g. menstrual cycle and hibernation (animals)

Ultradian Rhythms: under 24 hours e.g. BRAC or sleep cycle

D: generally rhythms can be considered interactionist due to interaction of exo zgs and endo pms

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Circadian (24 hours)

Maintained by endogenous pacemakers and influenced by exogenous zeitgebers, such as light, e.g. time we fall asleep and wake influenced by light but then endogenous pacemakers influence sleep-wake cycle

  • Siffre: 6 months in cave (self) therefore no exo zgs = day lengthened to 25 hours indicating free running 25 hour rhythm but factors such as light and temperature shorten to 24 hour cycle
    • experimenter bias: tested self, also case study and therefore cannot check consistency/not generaliseable
  • Folkard: 6 students in cave for 1 month = also lengthened to 25 hour cycle
    • support for Siffre, but small sample therefore cannot check for consistency
  • Folkard: 12 ppts in isolated conditions with strict mealtimes and bedtimes etc, but manipulated environment by gradually quickening clock to a 22 hour cycle = only one ppt adjusted to 22 hour cycle
    • support for bio rhythms as other 11 ppts had strong rhythms
  • Miles: man blind from birth has 24.9 hour cycle
    • supports influence of visual info (exo zgs) in rhythms
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Circadian (24 hours)

Endogenous Pacemakers in Sleep-Wake:

Darkness -> Retina -> SCN -> pineal gland (melatonin = sleepy) -> raphe nuclei (serotonin = suppressed by light) -> RAS (onset/arousal of sleep)

Evidence for SCN:

  • Ralph: mutant hamsters (20 hour) and adult hamsters (25 hour) had SCN transplants from other group = mutant with adult SCN developed 25 hour sleep wake cycle and vice versa
  • Damage to SCN in animals produces irregular patterns of eating and drinking and sleep wake

Evidence for melatonin:

  • Dose of melatonin in afternoon produces phase advance - sleep and wake earlier
  • Exposure to bright light in evening produces phase delay - sleep and wake later
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Circadian (24 hours) IDAs

A: Bio - endogenous pacemakers maintain cyclical nature of biological rhythms

D: Deterministic - suggests cycles such as sleep-wake are purely controlled by biological mechanisms and influence of environment, removes Free Will as suggests no control over behaviour; control over time sleeping or when we sleep?

I: Using animals in research - provides empirical evidence e.g. Ralph and transplanted SCNs, however as animals biologically and psychologically differ to humans research may not be generalisable to humans, possible ethical issue if causing distress e.g. by manipulating sleep-wake cycle in hamsters could be causing stress.

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Infradian (24+ hours)

  • Reinberg: one female in cave for 3 months = day lengthened and menstrual cycle shortened to 25.7 days
    • support for exo zgs in bio rhythms
  • Russell: daily sweat samples from females rubbed onto other females upper lips = synchronised menstrual patterns
    • support for exo zgs influencing endo pms
  • Pengelly and Asmundson: blinded squirrels in captivity with no cues to seasons etc (food always available, constant darkness and temperature) = hibernated at roughly same time
    • support for endo pms in maintaining bio rhythms even in absence of exo zgs

Reliable as consistent research, but low pop val due to biased small sample so cannot check consistency within studies.

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Infradian (24+ hours) IDAs

A: Bio as rhythms maintained by biological mechanisms (endo pms)

D: Determinstic as no contol over rhythms due to biological nature therefore suggests cannot control

I: Use of animals as differ to humans therefore not generaliseable (due to biological and psychological differences) and may cause harm to animals

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Ultradian (-24 hours)

BRAC (Basic Rest and Activity Cycles): peaks and troughs over 90 mins (attention, heart rate, eating), determined by exo zgs, particularly in adults who have longer BRAC than babies and small animals with fast metabolic rates.

Sleep cycle lasts 90 minutes and repeats 4-5 times during sleep. NREM = conserve energy and sensory info inhibited by hypothalamus. Broken down into stages of NREM sleep:

  • 1: heart rate/brain waves slow, muscles relax, feel like floating/falling then jerk awake
  • 2: sleep spindles (rapid high peak brainwaves), heart rate/blood pressure/body temp drop
  • 3: slow brain waves, deep sleep, breath and heart rate slow
  • 4: heart/breath rate/blood pressure/body temp lowest (sleep walk + talk)

1,2,3,4,3,2,REM: Rapid eye movements, beta waves sim to awake, high heart/breath rate and blood pressure, paralysed muscles and sexual stimulation e.g. erection, difficult to wake, dreaming takes place. Motor neurones inhibited (don't move) but sensory info can enter consciousness.

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  • Dement and Kleitman: sleeping ppts and EEG = 80/90% woken in REM recall dream, 7% NREM
    • reliable due to empirical evidence (EEG) but other studies indicate 70% NREM recall therefore contradiction
    • low eco val as in sleep lab therefore not same as real life sleep (electrodes on head etc)

Occurs as result of high acetylcholine and ends with increase in noradrenaline; certain drugs to treat depression increase noradrenaline levels thus eliminating REM, destruction of locus coeruileus eliminates REM (as produces neurotransmitters controlling REM)

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Lifespan Changes

Solely REM in foetuses at 30 weeks but 50% at full term, also 50% REM in newborns until 3 months when REM/NREM pattern established. Newborns sleep for about 16 hours, short sleep-wake cycle of 4 hours, due to feeding frequently, but by 6 months adapted to Circadian rhythm and reduces to 14 hours at one year with 45-60 minute cycle (increases to 70 minutes between five and ten years old.

Five to twelve years sleep for 9 hours with deep sleep in first half particularly due to maturing systems. REM decreases due to brain maturation and increased exercise. Sleep doesn't change much as a teen, but external influences are greater therefore less regular sleep-wake cycle. 18-30 year olds sleep less and may experience daytimes sleepiness due to less and shallower sleep = external influences.

30 -45

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Shift Work

Change to rhythm takes time for body to adjust, e.g. hormone production is over a week, therefore desynchonrisation of functions and rhythms (zgs remain same but rhythm changes) results in headaches, irritability, tiredness, therefore can be physically and psychologically detrrimental to workers, increases potential for accidents, reduces productivity

  • Green: reviewed nuclear disasters (Chernobyl: 1:23am, Three Mile Island: 4am) = during peak times for sleep impulse (body is most desperate for sleep)
  • Gold: nurses on rotating shifts = twice as many errors as those on permanent day/night shifts
    • both high eco val as RL, lack int val as measure effect of poor lighting etc not shift work
  • Czeisler: two groups of workers + new night shift; group with bright light + darkness from 9am-5pm = shifted sleep-wake rhythm 10 hours in 6 days compared to 1 hour change in other group

Easier to lengthen day than shorten day: rotate shifts forward (Czeisler). Permanent day or night shifts (Gold). Bright light in evening to stimulate workers (phase delay effect) (Dawson and Campbell)

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Jet Lag

Similar desynchronisation to shift work as change in time zones (exo zgs) = inability to sleep, tired during new day, decreased performance, etc.

Less jet lag flying West as temporarily lengthen day (phase delay better than phase advance)

  • Recht: basebal teams not crossing time zones = 46% games won, cross east to west = 44% won, west to east = 37% therefore debilitated due to jet lag
    • extraneous variables - other teams better, not jet lag? (low internal val)
  • Harma and Suvanto: 4 day flight, 10 time zones, 40 F flight attendants = sleepier over 4 days, slept less well, melatonin and body temperature desynchronised, body temperature resynchronised quicker than melatonin.
    • both high eco val as RL, however extraneous variables, e.g. in flight lack of sleep before flight? low oxygen in cabin or consumption of alcoholic beverages in flight? therefore lot int val + self report methods

A: Biological

D: Interactionist of NvN and Deterministic but element of Free Will due to coping methods e.g. melatonin supplement (Blakemore: fewer people jet lagged compared to placebo group, Takahashi: speeds up resynchronisation of rhythms)

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Fall instantly and involuntarily asleep for up to 20 minutes. Explanations include

  • Genes
    • Dement: 30% concordance rate of twins developing disorder
      • not clear if MZ or DZ; MZ = 100% expected (D: Diathesis Stress Model)
    • 2% Japan, 0.05% Europe therefore ethnic variations due to families (genes)
      • Mignot: contradict - no evidence of narcolepsy running in family or twins
  • Hypocretins: neurotransmitters associated with control of REM (therefore explains immediate REM in narcoleptic episodes)
    • Chemelli: GM animals with no hypocretin experience narcolepsy
    • Lin: sim to above but no hypocretin receptors experience narcolepsy
      • consistent: disruption to hypocretin process therefore support for explanation, empirical evidence
  • Link between genes and hypocretins:
    • Lin: narcoleptic dogs have mutation on twelfth chromosome disrupts processing hypocretins

D: Nature = A: Biological = D: Deterministic 

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Functions of Sleep (Evolutionary)

Sleep is adaptive as has not become extinct and different species has developed different sleeping patterns to survive e.g. only REM/NREM and REM, long/short periods of sleep.

  • Predator Avoidance: sleep when most vulnerable e.g. at night, in order to hide from predators (prey animals nap e.g. sheep = 2 hours, predators sleep for longer as safe)
    • Allison and Cicchetti: correlation between danger and amount of sleep (animals)
    • Benent: still and unnoticeable therefore safe from predators, but then why do humans snore? - animals differ to humans therefore nature and function of sleep may differ
  • Energy Conservation: animals with high metabolic rate use more energy = sleep longer
    • Zepelin and Rechstschaffen: correlation between body and sleep size (animals)
    • Hobson: less likely to find food at night therefore sleep instead of wasting energy

D: Nature as A: Evolutionary (genetic) = D: Reductionist as suggests purely for survival, no consideration of other factors

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Functions of Sleep (Restoration)


  • Oswald: skin growth at night and higher ATP (energy in cells) suggests growth at night etc
  • Adam: correlation between time in REM and heaviness (similar to Zepelin and Rechtschaffen)


  • Peter Tripp: no sleep for 201 hours = psychological symptoms e.g. hallucinations,brain waves same as in sleep (abnormal functioning) but after 24 hours sleep was fine (rebound effect: sleep longer for recovery but don't need to sleep for as long as lost)
    • high eco val as real life but extraneous variables, for example may have been mcrosleeping (not controlled)
  • Dement: cats on flowerpots in water so that everytime they fell asleep they fell off into the water and woke = experienced distressing symptoms and died (sleep deprivation)
    • low internal val: result of stress rather than sleep deprivation?
    • I: Ethics = distressing to animal, harm
    • Animals not generaliseable to humans
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