Sleep & Bio Rhythms

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Biological Rhythms

  • Bio rhythm= Physiological process running on a cycle
  • Ultradian= Less than a day 
    • Eg sleep cycle. Systematically move through phases of light/deep sleep following 90min cycle repeating 5/6 times a night
  • Circadian= Occurs aprox daily 
    • Eg sleep/wake cycle, light enters eyes (ez) to optic chiasm, SCN triggered where cells are that fire regularly. SCN signals pineal gland to release melatonin which=feelings of sleepiness
  • Infradian= Occurs monthly/annually, prepares us/animals to adapt to different seasons
    • Eg migration and hibernation in animals, SAD and menstrual cycle in humans
  • To reset= we get rid of exogenous zeitgebers
  • Exogeneous zeitgebers= external cue
  • Endogenous pacemaker= internal cue/body clock
  • Superchiasmatic nucleus in the hypothalymus (responsible for melatonin release)
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Bio Rhythms: Studies


  • Dement&Kleitman- Observed EEG in sleep lab, identified stages of NREM/REM sleep, rapid eye movement, beta waves, dreaming etc
    • Supports EPs as we all experience these stages of sleep in same order every time we sleep


  • Silver- removed SCN from hamsters, rhythms became erratic/desynchronised, suggests SCN plays role in circadian body rhythms
    • Good control but doesn't prove SCN=body clock, could be damage to other areas of brain that causes damage
  • So second experiment carried out where SCN fetal tissue implanted into hamster brains, slowly regained some pattern/regular circ rhythms
    • Reimplanting proves cause&effect/causual relationship between SCN & bio rhythms therefore study supports EPs role in bio rhythms
    • Animals, can't generalise as SCN may not have same role in humans
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Bio Rhythms: Studies cont'd

  • Issues/debates- ethical issues w/ animals however costs outweigh benefits (curing/helping with sleep disorders etc)
  • Nature based, doesn't take into account environmental factors etc
  • Siffre- Cave for 7 months, measured vital functions scientifically, found our brain runs on 25 hour clockbut sun 'resets' to 24
    • Evidence for EPs= still has cycle w/out EZs, evidence of EZ= 25 hour not 24
    • High int val, scientific measures not EZs provides strong support for theory
    • Difficult to generalise, restricted sample, unique case, biasbiasbias! May not apply to bio rhythms in everyday situations so low ext val
    • Issues/debates- psych as science, objective measures used to monitor bio rhythms so more reliable approach


  • Pengelly&Asmundson- Squirrels blinded from birth, kept in neutral environment, they hibernated @ same time as wild squirrels, but some hibernated a bit earlier each year
    • Evidence for EP= still hibernated w/out EZs, evidence for EZ= not fully acurate
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Bio Rhythms: Studies cont'd

    • High int val, provides strong support
    • Animals sp can't generalise to people (we don't hibernate/could work differently)
    • Issues&debates- ethical issues of blinding squirrels
    • Nature based, no nurture
  • Seasonal Affective Disorder (SAD)- Depression caused by lack of light in winter months, treated by light therapy and melatonin
    • Suggests EZs control/have role in controlling infradian rhythms
  • Russell et al- armpit sweat from one lady rubbed on anothers lips and periods synched which would be adaptive because pregnant @ same time
    • Evidence for EP= still have period even if it didn't synchronise
    • Evidence for EZ= external cues alter bodily rhythm 
  • Issues & debates of explanation-
    • Not reductionist!!!! because complex studies of EZs & EPs
    • Ethics w/ animals
    • Deterministic, suggests low serotonin, brain damage, genetic makeup cause aggression therefore removing free will/choice to deccide on appropriate action
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Disrupting Biological rhythms

Shift Work

  • Disrupts circadian rhythms by making people work when they should be asleep, forcing our bodies/minds to adjust to a new pattern. 
  • Internal synchronisation- different rhythms adapt at different speeds
  • 14% of people in UK work shifts, needs to be reduced to avoid disasters like Chernobyl
  • Forward shift rotation (better)=phase delay, day lengthens (eg morning/afternoon/evening)
  • Backward shift rotation= phase advance, day shortens (eg evening,afternoon,morning)
  • Biological clock= always trying to delay sleep by an hour a day, speeding up/working with body clock= better

Jet lag

  • Caused by rapid travel across time zones (plane) too fast for body to adjust to EPs
  • East to West= phase delay/day is longer (feels like staying up later), its easier 'cause of natural 25hour body clock
  • West to East= day shorter, phase advance (feels like going to bed early)
  • Jet lag occurs 'cause EZs working on advanced delayed time scale to EP
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Disrupting Biological rhythms: Studies

  • Shift Work
  • Cziesler- Lorry drivers day/evening/night pattern, disruption caused tiredness and bad/worse work, pattern changed to day/evening/night 3 weeks at a time, felt better, more productive etc. so forward shift rotation=best
    • High ext val, reflects real life therefore can apply to shift work patterns in real life
    • Culture bias, america, harder  to generalise
    • Low pop val, restricted to one proffession therefore cannot apply to all other jobs
  • Gorden et al- police went from back to forward shift, 30% less sleeping on the job, 40% reduction in accidents at work
    • Same issues as Cziesler tbh
  • Jet Lag
  • Schwartz- 2 baseball teams flown, E to W=44% games won, W to E 31% games won & bad jet lag symptoms, suggests phase delay easier to adjust to than advance
    • Hard to establish cause&effect, direction of travel or sporting ability? Doesn't tell us about affect of phase advance/delay/direction of travel
    • Culture/gender bias
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Disrupting Biological rhythms: Evaluation

Shift Work

  • Other than direction of shift, others suggest ways of reducing shift work consequences
  • Coren- rapid rotation is effective, Philips- suggested permenant shifts, Sack- napping @ work might help, but when beds were provided was not popular

Issues & Debates

  • Reductionist- Not reductionist because they consider range of factors (EPs & EZs) that can influence bio rhythms
  • Nature/nurture- There is an interaction between nature/nurture, because the conflict between EPs and EZs causes disruption to the bio rhythms
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Lifespan Changes in Sleep

  • Newborn
  • Babies sleep for 16-20 hrs a day, 50% in REM, premmie babies up to 80%
  • Endogonous bio rhythms are synchronised with EZs
  • Toddlers-Adults
  • At around 1 year kids sleep 6-8hrs a night = 1-2 daytime naps, REM= approx 25%
  • At 1-2 yrs sleep wake cycle established for up to adulthood
  • 70+
  • In old age sleep patterns change, night time fragmented (reduction in melatonin release also= day time sleepiness, napping) harder to fall/stay asleep
  • Older people= report more sleep disorders
  • Evaluation
  • Individual differences in sleep patterns
  • Don't fully understand reasons for changes in sleep patterns
  • We do not know the functions of these stages of sleep eg REM & NREM
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Theories of Sleep

Evolutionary explanation

Suggests sleep evolved into an essential behaviour because it provides selective advantages. Sleep doesn't serve a basic physiological function (sleep not strictly necessary) but has other functions (eg engergy conservation). Sleep=habit evolved to help fit into ecological niche which explains why different animals=different sleep patterns as it depends on various lifestyle factors:

  • Environment they live in effects their sleep patterns
    • Aquatic vs terrestrial- eg dolphins sleep one side of brain @ a time as adaption
    • Diurnal vs nocturnal- Active on set period every 24hrs, innactive for remainder
  • Predetor or prey effects sleep as prey animals=herbivores (mostly) so more vulnerable when asleep
  • Sleep site for prey tends to be relatively safe eg deep burrow
  • Size of animals effects sleep- bigger animals sleep less than smaller, but is it related to lifestyle or different physiology?
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Theories of Sleep

Evolutionary explanation

  • Predator Prey status- Meddis (1975), sleep keeps vulnerable prey safe, diurnal animals can't forage at night so sleep to keep safe (also no point being awake), animals at risk from predators evolved to sleep more to keep safe...key idea: sleep=effected by risk of danger, food gathering
  • Hibernation theory- Webb (1982), hibernation & sleep to conserve energy when foraging=difficult/impossible, animals inactive so conserves energy, animals w/ high metabolic rate use more energy & sleep more...key idea: difficulty food gathering and metabolic rate effect sleep
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Theories of Sleep

Restoration Theory

Oswald said sleep=necessary for survival, specifically it allows time for the brain & body to be restored.

  • REM sleep=essential for brain restoration, people recovering from drug overdose /newborns spend most of sleep in REM suggesting it restores the brain, brain energy consumption in REM=similar to awake suggesting this stage poses a restorative function
  • NREM=essential for body restoration, new skin cells grow quicker during sleep, probably due to increased growth hormones released during stage 4 of sleep, also stimulates repair of body tissue suggesting sleep poses a restorative function

Main predictions of the theory:

  • Deficits in functionnig when sleep deprived (no energy, can't do stenuous brain activity)
  • Rebound effects following sleep deprivation
  • Increase in REM sleep during brain growth, reorganisation & repair
  • Increase in SWS or REM when ill/injured
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Theories of Sleep: Studies

Evolutionary Explanation

  • Allison&Cicchetti- Studied sleep in 39 animal species & found that prey animals sleep way less than predators (opposing Meddis view sleep keeps them safe, but still evolutionary!), prey animals often herbivores & therefore need to spend most of their time grazing which might explain why they sleep less.
    • Supports evolutionary theory
  • Hibernation/energy conservation approach shows that BMR positively correlated w/ sleep time (higher BMR=more animal sleeps to conserve energy), small animals have higher BMR that large animals so sleep more
    • Supports Webb
  • Lesku- Analysed data on sleep patterns in 54 species, studied range of variables (body mass, brain mass, BMR, sleep exposure, herbivore or carnivore etc), found brain mass positively correlates w/ REM, sleep site negatively correlates w/ REM (^danger=v REM sleep)
  • So sleeptime & proportions of REM/NREM are influenced by a range of factors such as sleep sites/BMR/brain & body mass 
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Theories of Sleep: Studies cont'd

  • ...(Lesku) supports evolutionary because diff animals sleep for diff amounts of time 'cause they've adapted to survive in their ecological nische
  • Research=based on animals in natural habitat, high ext validity, subsequently gives good indication of effects of evolution on sleep cycles
  • Correlational evidence because unable to establish cause & effect therefore may not provide strong support/show effects of evolution on sleep cycles
  • Peter Tripp- (explained on next card) sleep deprivation caused extreme deficits/problems which it wouldn't have if evolutionary explanation was correct
  • Pilleri- Indus dolphins live in muddy waters and evolved blindness as eyesight= uneccesary, have excellent sonar to help find prey while dodging debris, despite dangers sleep has not dissapeared (sleep in short 4-60 second naps for 7 hours a day)
    • This is a problem for evolutionary approach 'cause if sleep just adaptive it'd have been eliminated instead of developing odd sleep/wake cycle/sonar to adapt
    • Controlled conditions to assess two captured dolphins so can assess sleep patterns/psychology as a science etc, high int val, objective, no ext variables therefore increasing support for idea that sleep isn't adaptive
    • Dolphins in captivity so might not be normal sleep patterns reducing validity
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Theories of Sleep: Studies Cont'd

Restoration theory

  • Ryback&Lewis- Volunteers spent 6 weeks in bed, found no change in sleep patterns
    • Theory would predict less need for sleep/stage 4 if unactive, but wasn't the case
  • Shapiro- Studied marathon runners (57 mile run), found they slept for extra 1.5 hrs for 2 nights after, stage 4 took up approx 45% where it usually is 25%
    • Supports idea that stage 4 sleep is needed to restore the body
  • Peter Tripp- Spent 201 hrs awake, short term= hallucinations, irritability, altered state of conciousness, brain waves like REM when asleep, drop in body temperature, long term=lost job, divorce, no longer himself (may not have been related to sleep deprivation)
    • No time to recover/restore body/brain so his body forced him into REM while awake which suggests we need it
    • High int val (controlled every last detail) therefore can be generalised
    • Case study, low pop val + biases means it's hard to generalise
  • Randy Gardener-264 hrs of sleep deprivation, some hallucinations but that was pm it
    • No psychiatric problems...was that just Tripp's individual reaction? 
    • Supports theory 'cause caught up on REM/stage 4 sleep afterwards however no long term effects... 
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Theories of Sleep: Studies Cont'd

    • (Gardener), Wasn't monitored till after 80hrs so may have slept
    • Case study problems
    • But still unsure if effects of sleep deprivation same w/ everyone
      • Fatal familal insomnia where no sleep= death?? Supports theory
  • Jouvet- Cats on flowerpots over water, in REM sleep they fell into water, woke up & climbed back on pot, cats became conditioned to wake up before REM to prevent this
    • Cats exhibited odd behaviour (hypersexuality, no control of body temp) and died
      • Ethical issues of killing cats
      • High internal validity
      • Animal research, so hard to generalise to humans
  • Rechtschaffen- used yoked-control procedure to deprive rates of sleep, two groups of rats, control=same amount of stress as experimental, but provoked at random times, whereas experimental rats provoked as soon as they fell asleep (sleep deprived)
    • Control=perfect health, experimental became weak, uncoordinated, weak, developed sores that wouldn't heal, weird body temp, lost weight and died after approx 16 days
      • ethics
      • high int val, lots of control
      • suggests sleep is essential to function, supports theory
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Theories of Sleep: Evaluation

Alternative explanations: (each other lol)

Issues & Debates

  • Reductionist-Evolutionary is not reductionist as it incorporates range of environmental factors that may affect sleep patterns in animal kingdom, able to explain why diff animals sleep in diff ways. Restoration is reductionist as it only considers bio factors as explanation of sleep, can't explain differences in sleeping patterns between animals
  • Nature/Nurture-There is an interaction between nature/nurture in the evolutionary explanation, however in restoration theory the focus is on nature
  • Psychology as a science-Restoration theory in particular uses a range of scientific objective measures such as EEG machines to monitor changes in sleep patterns as a result of sleep deprvation, as such the findings of these investigations are significantly more valid than research into the evolutionary approach
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Sleep Disorders: Insomnia

  • Dyssomnia- Problem with amount/quality/timing of sleep, often produces daytime tiredness
  • Parasomnia- Behavioural/physiological events that occur during sleep, rarely associated with daytime tiredness

Insomnia is a dyssomnia, and there are two types;

  • Primary Insomnia- Chronic insomnia occuring in the absence of psychological/physical conditions that might explain the disorder. Most extreme form of primary insomnia is idiopathic insomnia
  • Secondary Insomnia- Chronic Insomnia that can be explained by a pre existing medical condition; psychological disorder, parkinsons disease, drug use, fatal familial insomnia etc
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Sleep Disorders: Insomnia

Explanation #1= Anxiety & Personality Factors

  • Primary insomnia has been linked w/ people w/ higher than avrge anxiety.
  • People with the personality trait neuroticism= greater risk of secondary insomnia, nuerotic person characterised by obsessional thoughts, compulsive acts & physical complaints without any objective evidence of illness
  • A person's chronotype can also affect the development of insomnia. Eg w/ Larks and Owls, Owls are at a greater risk of insomnia as the 9-5 routine doesn't intergrate easily w/ their internal body clocks preferred routine

Explanation #2- Sleep Apnoea

  • It's a disorder where a person stops breathing while asleep, pauses lasting from a few second to minutes, occuring 5-30 times a night
  • Obstructive sleep apnoea is caused by airways being blocked (narrowing airways or enlarged tissue at the back of the mouth)
  • Central sleep apnoea is linked w/ heart problems & is probably caused by a malfunction in the brains control of the repiratory & heart functions

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Sleep Disorders: Insomnia cont'd

Explanation #1 studies-

  • Vgontzas- Found insomniacs have increased levels of ACTH (hormone linked with long term stress) & cortisol, & reducing aroual is usually effective. Suggests stress leads to insomnia
    • Can't establish cause & effect
  • Vahtera- Found vulnerability to sleep disorders after traumatic life events= highly correlated with personality trait anxiety
  • Gregory- Study on 1000 children followed up from birth to 34 yrs old, studied variables such as levels of family conflict in questionnaires measuring tension/hostility/distress/ bad experiences. Found family conflict between 9 & 15 significantly correlated w/ frequency of insomnia at 18, concluded a possible relationship between family conflict & later sleep problems. Insecurity may lead to high levels of anxiety/tendency to focus on family difficulties (fits in with research showing insomnia=linked with anxiety
    • High int val, control variables eg gender, health, depression etc
  • Jansson-Frojmark & Lindbolm- Found link between depression/anxiety/insomnia
    • Depression/anxiety could be cause and/or effect of insomnia
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Sleep Disorders: Insomnia cont'd

Issues & Debates

Ethics- Longitudinal studies like J-F & L have parents consent from birth, kids consent at 16

Reductionist- Theories of insomnia= not reductionist, take range of factors into account eg personality/biological factors/environmental factors, to explain insomnia, however simply using one explanation for the onset of insomnia is reductionist (eg chronotype) as it only focuses on one cause

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Sleep Disorders: Sleep Walking

Sleep walking is a parasomnia, (doesn't lead to day time tiredness), occuring during NREM stages 3 & 4 early in the night, cannot happen in REM as muscles= paralysed

Explanation #1- Psychodynamic (Freudian)

Desire to sleep where you did as a child, sleep walking is acting out unconcious desires, Freud also suggested that we work through unconcious anxieties during REM, if they haven't been succesfully delt with in this stage they will spill over into NREM and are challenged into motor activities such as sleep walking

General Evaluation- Cannot explain the automatic acts sleepwalkers carry out (eg making tea), this explanation can't be experimentally tested & is therefore unfalsifiable

Explanation #2- Genetics

There's some evidence that sleep walking= genetic, sleep walking should occur in families with history of the disorder & that MZ twins show high concordance rates of the disorder

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Sleep Disorders: Sleep Walking Cont'd

Explanation #2 Studies

  • Bakwin- Studied frequency of sleep walking in 19 MZ/14 DZ twins between, found concordance rate of 47% in MZ twins, 7% in DZ twins, supports genetic explanation, but concordance rate not 100% so there must be environmental factors involved. Also found tendency within families for sleep walking, far more siblings of MZ sleepwalkers walked in their sleep than would be expected from the general population
  • Hublin- Finnish study of 11,000 p's between 33-60 yrs, answered q's about frequency of sleepwalking, found males genetic influence= 66% in childhood & 80% in adulthood, females= 57% in childhood & 36% in adulthood
    • (meaning if parents sleptwalked as a child son has 66% chance, if sleptwalked as adult 80% chance of sleepwalking)
    • Large sample size, no gender bias
    • Culture bias
    • Concordance rates (not 100%)
    • Retrospective (about things that have already happened)
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Sleep Disorders: Sleep Walking Cont'd

Issues & Debates

Reductionist- Genetic explanation reduces complex behaviour into simplistic explanation, genetic predisposition. Cannot explain variety of tasks carried out in sleep walking & doesn't provide full explanation

Nature/nurture- Genetic approach focuses on biological explanations for behaviour, however concordance rates in MZ twins are not 100% suggesting nurture plays a part in explaining sleep walking too, therefore genetics doesn't provide full explanation

Determinist- Both genetic & psychodynamic explanation suggest sleep walking can't be controlled- genetic predisposition or unconcious desires drive behavour (removing free will)

Psychology as a science- Psychodynamic approach can't be tested objectively, evidence for this approach comes from subjective interpretation as such the theory can't be falsified, so it isn't scientific

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Sleep Disorders: Narcolepsy

Narcolepsy is a dysomnia, begins in early adolescence/adulthood & continues throughout life, about 1 in 2000, but many are undiagnosed when only minor symptoms are present.

Explanation #1- REM system malfunction

Malfunction in the system that regulates REM, a lot of symptoms if narolepsy are experienced to some extent during a REM cycle

  • Cataplexy (loss of muscle tone while concious)
  • Sleep paralysis (inability to move at the start/end of sleep)
  • Sleep stages (narcoleptics fall straight into REM & spend most time asleep in REM)
  • Extreme daytime tiredness (they have less NREM)

Explanation #2- Orexin

Orexin is a hormone responsible for wakefulness & control of REM sleep. It is believed that a lack of orexin/orexin receptors may be responsible for narcolepsy in humans

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Sleep Disorders: Narcolepsy Cont'd

Explanation #1 studies

  • Siegal- Found that cataplexy in narcoleptic dogs is linked to the activation of cells that are usually only activated in REM sleep
    • Dogs, so difficult to generalise findings

Explanation #2 studies

  • Wickens- Found orexin is involved in controlling REM sleep
  • Dog studies- Narcoleptic dogs have tendency toward cataplexy when excited, also fall straight into REM. Through selective breeding they found that a gene defect is responsible, the gene responsible for regulating brain receptors for orexin
  • Nishino- Found narcoleptic humans have low levels of orexin in cerebrospinal fluid
  • MZ twins- Doesn't support the explanation because whilst higher than DZ twins concordance rate is still only 30% suggesting enviromental factors as well
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Sleep Disorders: Narcolepsy Cont'd

Issues & Debates

Reductionist- They assume narcolepsy is only caused by activation of cells/malfunction in REM systems as it doesn't take into account other important factors

Nature/Nurture- Focus on biolgical explanations for behaviour, very little consideration for environmental factors that could play a role in explaining narcolepsy eg why different emotional states may be linked with onset of narcoleptic episodes

Ethical Issues- Selective breeding of animals is iffy, specifically manipulating genes to cause disorders, however the research has allowed psychologists to investigate a potential explanation that can't be researched on humans & it could lead to successful treatments for narolepsy therefore benefits outweigh the costs

Psychology as a science- The suggestion that orexin levels in the brain are linked with narcolepsy allows us to create testable hypothesis & investigate them using objective methods, subsequently this approach is scientific

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