Theories Of Sleep

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Evolutionary Explanation of Sleep
Lifestyle factors
- Aquatic vs terrestrial
- Diurnal vs nocturnal
- Predator or prey
- Sleep site
- Size
Evolutionary Explanation of Sleep
Meddis (1975) Predator Prey Status THEORY
Sleep keeps vulnerable prey animals safe when normal activties impossible
Diurnal can't forage at night, sleep evolved to keep safe from predators
Amount of time animal sleeps depends on safety of sleeping site and how much time spent getting food
Evolutionary Explanation of Sleep
Webb (1982) Hibernation THEORY
Emphasises importance of energy conversation
Animals hibernate to conserve energy when hunting and foraging are impossible
Inactive during sleep
Evolutionary Explanation of Sleep
Allison and Chicchetti (1976)
Prey animals sleep significantly less than predators oppose Meddis
Basal Metabollic Rate positively correlated with sleeping timet supports Webb
Evolutionary Explanation of Sleep
Lesku et al (2006)
Herbivores had less REM and total sleep time
BMR negatively correlated with NREM and total sleep time
Evolutionary Explanation of Sleep
Pilleri (1979)
Indus dolphins have evolved blindness, despite dangers from floating debris still have short naps
4-60 seconds 7 hours a day
If sleep served adaptive function would have been eliminated through natural selection
Evolutionary Explanation of Sleep
Alternative Explanation
Restoration Theory
Restoration Theory of Sleep
Sleep essential for restoring body and mind
REM - Essential for brain restoration. People recovering from drug overdose spend most time in REM, newborns spend 1/3rd sleep in REM. Brain energy consumption similar in REM as waking behaviour
NREM - Essential for restoration of body, new skin cells grow more quickly during sleep. Increased release of growth hormones during stage 4, stimulates repair of body tissue
Restoration Theory of Sleep
Shapiro (1981)
People who completed ultra marathon slept extra 1.5 hours 2 nights after race and stage 4 sleep took up greater proportion of total sleep time
Restoration Theory of Sleep
Ryback and Lewis (1971)
Healthy volunteers who spent six weeks in bed had no change in their sleep patterns
Restoration Theory of Sleep
Peter Tripp
Long term effects:
- Divorced
- Lost job
- Drifted
Short term effects:
- Hallucinatiosn, spiders in shoes
- Irrational behaviour
- Psychotic
- Altered state of conciousness
Restoration Theory of Sleep
Alternative Explanation
Evolutionary approach
Theories of Sleep
Issues and Debates
Reductionist - Evolutionary NOT reductionist as it incorporates range of environmental factors, able to explain why different animals sleep in different ways. Restoration theory IS reductionist as it only considers biological factors
Nature/Nurture - Interaction between nature and nurture in Evolutionary whereas restoration focuses on nature
Psychology as a science - Restoration theory uses range of scientific objective measures, findings significantly more valid in research

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