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  • Created on: 23-12-15 11:37

Stages of Sleep

Research Evidence - Dement & Kleitman [LAB EXPERIMENT]

  • 9 sleeping participants / 61 nights -- woken at different stages of sleep
  • Dreaming in REM: 80 - 90% /// In NREM: 7% = RELIABLE CONSISTENCY

Measures of REM and Dreaming Different

  • REM + Dreaming qualitatively different -- QUESTIONABLE FINDINGS
  • REM: physiological + objective // Dreaming: Subjective interpretations + Not objective 


  • Stood the test of time - accepted by scientific community BUT 70% dream in NREM - QUESTIONS RELIABILITY
  • Foulkes: Confusion what constitutes a dream -- vague dream-like experiences/muddled thoughts

Psychology as a Science

  • Controlled -- enhance replicability + objectivity -- CONFIDENCE in findings
  • Critics: artificial - lack generalizability - demand characteristics - RESULTS STILL CONSISTENT = SOLID
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Lifespan Changes in Sleep


+ ADAPTIVE -- Babies sleep during the day to allow parents to get on with chores  = enhance survival /// Nightwaking to be fed regularly

+ BRAIN DEVELOPMENT - Spend more time in REM and it's linked to production of neurotransmitters and consolidation of memories. Premature babies: 90% in REM 

Childhood + Adolescence:

+ LINKED TO HORMONES - Hormones released at night - sleep disturbed = sleep deprivation // Symptoms of sleep deprivation similar to puberty: irritation, moodiness, changes in school perf., changes in motivation 

However that's REDUCTIONIST - various external pressures - CORRELATION still has FACE VALIDITY

Adulthood + Old Age

+ RED SLEEP LINKED TO PHYSIOLOGY - problems staying asleep: less growth hormone - less deep sleep // Symptoms: lack of energy, lower bone density -- however sleep apnoea and other medical illnesses are present

Need to be HOLISTIC - more knowledge = more effective treatment -- relaxation techniques and taking melatonin

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Nature of Sleep - GENERAL

Objective Measurements

  • Research replicated + reasonably well established. However it involves the measurement of sleep which means connection to electrodes = affecting quantity + quality. More than one night in the lab to ADJUST

Population Validity

  • External validity - lack of research into NORMAL SLEEP among the MIDDLE AGED -- too busy so find less time to volunteer which is ironically why they need to be studied = GREATEST sleep problems

External Factors + Co-Sleep

  • Work patterns, children, aches, pains, medication + sleeping w/a partner = effects under researched = practical difficulties in a lab but co-patterns may be both qualitatively + quantitavely different from sleeping alone

Cultural Differences

  • Northern + Central Europe + North America: MONOPHASIC /// Mediterranean + Central + South America: POLYPHASIC (w/siestas - avoiding work in the hottest parts of the afternoon} Brobley: 42% Greeks polyphasic
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Circadian Rhythm

Research Evidence For Role of Endogenous Pacemakers

Michel Siffre - 7 months underground - adequately fed / opportunity to exercise / make contact via phone but NO cues // Natural circadian rhythm JUST OVER 24 HOURS - patterns of sleep/wake persist even w/out exogenous zeitgebers

Methodological Issues

Siffre - taking care when generalizing the findings from case study > small sample = population validity is a WEAKNESS // He was a volunteer - already motivated + fully aware of the nature of the study

Ethical Issues

No one could predict the effects on him -  feelings of depression, suicidal thoughts and memory problems (80 days)

Further Supporting Evidence

Folkard - strong free running internal clock / 12 people / 3 weeks / NO natural light + other cues / UP @ 7:45 /// ASLEEP @ 11:45 & quickened: 24 hours after 22. Originally matched but as it quickened, stayed 24H - guided to a LIMITED extent 


Participants not isolated from artificial light - CZEISLER: Altered down to 22 and up to 28 w/dim light -- CONFOUNDING

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Endogenous Pacemakers

Research Evidence for Role of Endogenous Pacemakers

MORGAN: SCN removed from hamsters - rhythm disappeared // mutant hamsters bred (rhythm 20h) // those SCN's transplanted into normal hamsters = exhibited 20h circadian rhythm

Use of Animals - careful extrapolating + important application to human beh. then animal harm would be acceptable 

Lacks Eco Validity - lab conditions - replicable but may not be displayed in a less contrived environment = cant generalize

Evidence for Role of Melatonin

Smith-Magenis Syndrome: levels of melatonin inverted - rises in early morning - take supplements to help w/symptoms


Reducing the behavior to one component -- can infer cause and effect // however, gain a much better understanding of bio rhythm if we move just beyond endogenous pacemakers and look at other ext. factors: light, temperature, social cues

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Exogenous Pacemakers

Light Main Zeitgeber Blind man struggles to maintain 24h rhythm (24.9h) - needs stimulants + sedatives to get his biological rhythm on time. Difficulty functioning with daily routines despite exogenous zeitgebers

Reliability - CAMPBELL & MURPHY: different route to the SCN - through the back of the knees (via the skin / blood)

Light Not Only Exo Zeitgeber - LUCE & SEGAL: Arctic Circle - sleep 7 hours during each 24h period // LOBBAN: Rural Inuits - natural tendency to make the most of longer summer days // result of availability of social synchronisers (eating behavior and social customs) 

Advantage of Endogenous Pacemakers - Without Them @ Mercy of Environment

Not present - might sleep most of the day in winter + get less sleep in the summer // Main disadvantage: wont change when you need them to (like travelling across timezones) 

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Infradian Rhythms

Supporting Evidence

RUSSEL et AL: Effects of pheromones - daily samples of sweat collected from one group of women + rubbed on upper lips of other women = cycles become synchronized w/individual odor donor. (BENTLEY: evolutionary advantage)

Conflicting Evidence Women's basketball team - no correlation - exercise, dieting and stress can each cause changes 

Methodological Issues - Rely on recall = may be inaccurate / social desirability / if errors corrected = no synchronisation


Pre-Menstrual Symptoms: legal defence for some women who have committed offences. 

Dr. Katherine Dalton - akin to a mental disorder - cannot be held responsible. HOWEVER the suggestion that women have no control over their behavior when suffering from PMS may be open to abuse.

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Ultradian Rhythm

Research Evidence

Dement & Kleitman - the 9 participants 61 nights study w/Dreams

Psychology as a Science

Physiological meausres gathered in a sleep lab - artificial conditions + wired up to machines = affects sleep patterns


70% of those in NREM reported dreams // Foulkes' confusion as to what constitutes a dream


Alter our bio rhythms at will -- individuals who can control what happens in their dreams: LUCID dreaming - v. rare // Demonstrates that even when asleep, we are not completely determined by our biology + can exercise choices

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Disruption: JET LAG

Research Evidence - KLEIN et al -- passengers flying EAST TO WEST: 1 day readjustment // WEST TO EAST: 6 days -- travellers struggle with PHASE ADVANCE more than PHASE DELAY 

Further Research Evidence - RECHT et al - US baseball team over 3 YEARS / EAST to WEST: won 44% of games // WEST to EAST: won 37% of games ((some teams may have been better than others - length of study should've evened)

Biological Determinism - People can override their physiological drive to sleep by forcing themselves to adopt social rhythm of the destination - FULLER: period of fasting, followed by eating on the new times  = ENTRAIN rhythm

Practical Application - Melatonin - APPLIED to combat negative consequences of disruption - BEAUMONT: melatonin given at bedtime significantly reduces the symptoms of jet lag

Reductionist - Jet lag may be affected by other factors - sleep badly the night before, travel itself being tiring, long hours of getting to the airport, drinking alcohol or coffee, constant nioce, low-oxygen cabin air, annoying passengers. 

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Disruption: SHIFT WORK

Practical Application: Change type of shift system - MOST problems w/ ROTATING shifts that alternate every few days // Non-fluctuating shifts - less disruptive - one sleep-wake pattern 

Experimental Support: CZEISLER: Utah Chemical Plant / high rate of health problems, sleeping diff, work-related stress in staff on SHORT rotation shifts. PHASE DELAY is better + inc. shift rotation to 21 days. 9 months in: satisfaction increased, accidents reduced and factory output higher. 

Practical Application: CZEISLER: bright lights can reset bio rhythm within 3 days -- strong lights entrain all rhythms not just the sleep-wake cycle: POSITIVE application

Hawthorne Effect: Problem generalizing to everyday life - participants v motivated + know theyre being monitored

Practical Application: Night shift workers improve quality of their sleep during the day - quiet + dark bedroom + avoid bright lights. Can be v disruptive to other family members

Reductionism: Social factors must be considered - social disruption too - SOLOMON: divorce rates as high as 60% among all-night workers

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Disruption: GENERAL

Methdological Issues

Field studies - high ecological validity - MANY confounding variables: personality + other individual differences not controlled // more difficult to reach firm conclusions

Individual Differences

Effects of disruption may vary considerably - examples where disrupting rhythms had dramatic effects w/out any obvious effects on their cognitive abilities = attention + concentration or emotional well-being. Those with least changing rhythms = cope best overall. 

REINBERG et al: People who gave up shift work because they couldnt cope tended to have rhythms that changed a lot while o shift - whereas 'happy shift workers' had unchanging rhythms

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Restoration & Repair - Oswald

Research Evidence - fairly anecdotal - based on individual case studies - deprivation produces effects on memory and attention (and hallucinations + paranoia) Evidence strongest for restoration of brain processes. 

PETER TRIPP: NY DJ - didnt sleep for 8 days, paranoid delusions + halucinations - hard to test level of psychological functioning. AFTER: slept for 24 hours - awoke feeling restored ((Suggests he suffered psych cons. months/years later)

Case Studies - Lack generalizability + sleep deprivation OR individual / DEMENT: severe effects resulted from experimental effects - when warned of potential side effects = demand characteristics

Research Evidence - EXERCISE + SLEEP : SHAPIRO: Runners in a marathon slept for 1 1/2 hours longer for 2 nights after the run. Stage 4 sleep INCREASED - fits that NREM is for physical recovery. HORNE: sleep faster but not for longer

Contradictory Evidence - Failed to produce conclusive evidence that sleep is necessary to keep body functioning normally / HORNE: 50 controlled lab studies - deprivation - interfered with ability to perform physical exercise. Sleep for BRAIN FUNCTION ONLY -- when allowed to sleep: recovered more of REM and deep NREM than light NREM.

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RESTORATION: Core & Optional Sleep - Horne

Research EvidenceRandy Gardner: 17 yr old student, 11 days awake, difficulty performing tasks, didnt produce severe disturbances. AFTER: Slept for 15 hours - recovered 25% of lost sleep (70% in deep NREM & 50% in REM) = special important = supports Horne

Psychology as a Science - Little control in the study - periods of microsleep - dev. of sleep labs excellent example of how study of sleep functions in humans become more objective + scientific EEG + physiological measures recorded constantly - RELIABLE results

Evidence Supproting Role of REM in Restoration of Brain NeurotransmittersStern & Morgane Observed that REM deprivation led to REM rebound - inc. in REM - vital for brain recovery

Animal Studies - Sleep deprivation may have fatal consequences -- RECHTSCHAFFEN et AL  forced rats to remain physically active by rotating a disc that they were standing on everytime they started going to sleep = stress rather than lack of sleep (depriv. interferes with immune system => death)

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Use of Non-Human Animals

Raises problems of generalising from animals to humans - diff. sleep requirements + patterns


Focusing only on physiological processes - if theories extended to non-human animals then ecological factors included. YOUNG: more we know about sleep patterns of other species - more apparent that environmental pressures rather than restoration provide the key to understanding sleep.

Role of NREM and REM

Energy expenditure in REM is similar to waking levels - neurotransmitters restored during REM however it invovles considerable brain activity it's diff. to see how they would be restored - if anything they're being used up during REM sleep. 

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Energy Conservation - Webb

Supporting - Zeppelin & Rechtschaffen - Metabolic rate and animal size did relate to time spent sleeping in many species w/smaller animals w/higher metabolic rates sleeping longer than larger animals. BATS: 20h whereas GIRAFFES: 1h 

Extrapolation from Non-Human Animals - Giant sloth sleeps for far longer in the zoo than it does in its home environment. Wild animals sleep less than captive animals: more concerned w/predation + spend more time foraging.

Is Rest As Adaptive As Sleep - Amount of energy conservation in sleep is minimal - red. energy rates at best by 5-10% compared to simply resting. This suggests rest is as adaptive as sleeping. Risks associated w.sleep = outweigh marginal advatange of energy conservation. Energy conservation isnt sufficient to explain the complete function of sleep.

Corerlation - Not demonstrating a casual relationship between sleep and energy conservation / difficult to disentangle correlations between variables. Cannot say for certain which variable is more important in determining sleep time.

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Predator Avoidance - Meddis

Research Evidence

Sleep analysis of 39 species - negative relationship between risk of predation and amount of sleep. Carnivores sleep more (16h) and prey sleep less (3h) - there are exceptions though - rabbits sleep as much as moles

Waking Inactivity

Would do the same job with less vulnerability to predation. However, loss of consciousness ensures greater stillness than inactivity alone. Some species have adapted the need to both sleep and maintain vigilance - UNILATERAL SLEEP - why not in all species? Evolutionary advantages not great eough.

Psychology as a Science

Difficult to test scientifically - sleeping for longer or for shorter can both be seen as adaptive for species in danger. Unfalsifiable evolutionary theories - impossible to test directly + purely speculative

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Not Reductionist

Takes the whole animal and its lifestyle into account (foraging, avoidance, safe sleep sites, energy conservation) 

Role of NREM and REM

Cannot explain why we need both. Energy conservation is the main function - makes sense to need NREM but REM energy consumption is only slightly less than waking behavior. Larger animals with lower metabolic rates, have less NREM bc dont need to conserve as much energy. Sleep must have alternative functions than just energy function.

Persuasive Argument

Sleep is still found in species that would seem better off without it (INDUS dolphin) - blind bc good eyesight is not necessary given the poor visibllity of its environment. Sleeps in short naps between 4 and 60 seconds for a total of 7 hours each day. If it was merely adaptive - surely it would have been eliminated through process of natural selection

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Primary Insomnia

Evidence for Classical Conditioning - Sometimes cant sleep in their own bed but can sleep while watching TV or away from home. Learned associations - are not present in the unfamiliar sleep environment. Few nights of interrupted sleep per month can be enough to produce a cycle of poor sleep + inc. worry about it. 

Practical Application - Attribution Theory - the belief that they're going to have difficulty sleeping - if people can be convinced that the source of their difficulty lies elsewhere will end their maladaptive attribution. Insomniacs given a pill that will allegedly stimulate them or act as a sedative - those expecting arousal went to sleep faster bc attributed arousal to the pill and actually relaxed.

Nature/Nurture - Genetic vulnerability - physiological factors may predispose a person to develop insomnia - Hyperarousal: makes it more difficult. However, predisposing factors alone are unlikely to explain chronic primary insomnia = diathesis stress model -- environmental stressors trigger the disorder

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Secondary Insomnia

Not A Disorder DEMENT: not a disorder but a symptom - could be the effect of other psychological, physical or environmental factors = may in fact be the cause. Study: 15,000 Europeans found insomnia more often preceded rather than followed cases of mood disorders = might be helpful to treat insomnia regardless of whether it's primary/secondary

Difficulty Generalizing - Highly complex + unlikely to be explained by one single factor -- so many different causes: stress, depression, poor sleep hygiene (red. caffeine intake, sleeping in a darker room, cutting down daytime naps, inc. exercise), age, gender and so on. Impossible to make generalizations. 


Reliability and Validity of Sleep Insomnia Measures: Controversy over identification of insomnia - tend to overestimate their sleep problems: MERCER: Individuals greatly overestimate the time it takes them to fall asleep + underestimate how long they've slept. Subjective self-report should not be overly relied on,

Primary or Secondary: Important to distinguish between primary + secondary insomnia bc of the implications for treatment. Insomnia symptom of other disorder then it's important to treat the disorder rather than the insomnia. Many people suffering from depression begin to experience improved sleep after taking antidepressant pills eventhough they have no effect on sleep patterns of those not depressed

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Supporting Evidence - VOGEL: observed REM at the onset of sleep in a narcoleptic patient - supported by recordings of neural activity in the brainstems of narcoleptic dogs that showed cataplexy is linked to the activation of cells that in normal animals are active only during REM. 

Evidence for Hypocretin - Human studies: Narcoleptics: lower levels of hypocretin in cerebrospinal fluid - hypocretin producing cells are drastically reduced (93% reduction) 

Effective Treatment - The drug Modafinil (stimulant) - useful in treating the disorder - works by activating the nerve cells that contain Hypocretin. Lends support to the genetic explanation that hypocretin deficiency can explain onset

Evidence for Genetic Component - Weak genetic component - 1-2% of first degree relatives were also narcoleptic, compared to very low rates in the general population. Most dont have a relative w/the disorder. MZ's concordance: 30% (4 out of 16) - not entirely inherited and that environmental factors are also important.

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Narcolepsy - GENERAL

Nature v. Nurture

Caused by a combo of genetic susceptibility + one or more environmental triggers. PICCHIONO: several stressors inc. change of sleeping habit, flu, unexplained feber = sig. risk for narcolepsy

Use of Animals

Bred narcoleptic dogs - cant generalize non-human research as the inherited nature of narcolepsy has been shown to be qualitatively different in humans compared to dogs. In humans there is no clear gene - and the breeding of dogs to study sleep disorders is an emotive topic and scientists have to weigh up the costs and benefits of such programmes.

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Evidence for Genetic Component BROUGHTON: First degree relatives of an affected person: 10x greater than in general population. 50% for MZs & 10-15% for DZs. Gene found - only 50% of sleep walkers + 25% general population. (Not only)

Evidence for Neural Component OLIVIERO: Motor excitability of adult sleep walkers during wakefulness: signs of immaturity in the relevant neural circuits related to motor control. May be a biological phenomenon.

Sample - Not representative of the general population - most dont seek help or come to the notice of researchers since they're not aware + dont find it causes them a problem. Those who seek help are those who have been injured (qualitatively different from the rest of the sleep walking population)

Free Will + Determinism - Canada 1980s - Ken Parks pleaded not guilty to murdering his mother-in-law on grounds he was sleepwalking and jury acquitted him. Biological determinism - cannot control behavior

Alternative Explanation - Psychodynamic explanation sleepwalking + nightmares > superficially convincing. However explanations such as instinctual energies spilling over from REM to NREM dont lead to hypothesis that can be tested

Diathesis-Stress Model - Diathesis (genetic predisposition) + stress can be linked to risk factors that can precede sleep walking such as deprivation, alcohol and fever

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