Theories of sleep & dreaming Mark Illingworth & Emma Pearch Why do we sleep? For AS you need to know 2 theories of sleep: • Evolutionary Theory Evolutionary Theory ---Survival of the fittest (genes)--- • MEDDIS (1979): (1979) – Researched into the relationships between sleep patterns of predatory animals and their prey. – Found that prey sleep for less time than predators as being at an alert state as much as possible is essential to the prey’s survival. – Humans have evolved to sleep at night because without our eyesight we not only lose our productivity but we also become prey. • WEBB: – Looked at cases of prey that can sleep for lengths due to the safety of burrowing etc (e.g. Rabbits). – In circumstances where we can be relatively sure of our safety during sleep, we can then also sleep longer. Evaluating Evolutionary Theory + Similar animals sleep in similar ways. (i.e. reptiles do not have REM sleep - due to the less developed hypothalamus.) + Some animals have evolved their sleep patterns to adapt to their environments. - Surely if alertness is the question, why haven’t we evolved not to sleep? Then we could be vigilant 24/7. - This theory has no explanation for the different cycles of sleep which have been proven to occur. - We can’t test this theory, well, until someone invents a time machine so that we can observe changes in human sleep patterns over time. Why do we sleep? For AS you need to know 2 theories of sleep: • Evolutionary Theory ~~Survival of the fittest genes over time~~ • Restoration Theory Restoration Theory ~~Exertion requires regeneration~~ • OSWALD: – Looked at how the body recovers most during sleep, with peak levels of protein synthesis in cases for the recovery of the body as well as general growth. – ‘We need to sleep to restore ourselves physiologically and psychologically’ Evaluating Restoration Theory + All hormones work more effectively at night. + After 5/6 sleepless nights, delusions and other psychological problems are known to develop. + The youngest and oldest people sleep much less as with their lesser exertion, they require less restoration. + SHAPIRO: Studied marathon runners, who due to their massive exertions, required longer sleeping times to restore their bodies. - REM sleep is where the brain is often at its most active, so brain energy must not be being conserved. - Sleep studies are hard to certify as there can be many external factors that affect sleep. - RYBACK & LEWIS (1971): - Kept active people in a room and told them to do nothing, the participants were expected to not need to sleep due to the lack of exertion, but they did sleep. Why do we sleep? For AS you need to know 2 theories of sleep: • Evolutionary Theory ~~Survival of the fittest genes over time~~ • Restoration Theory ~~Exertion requires regeneration~~ [SORTED! – Onto the Dreaming then! Only need one of those!] Reprogramming Theory ~~Further processing new information~~ • EVANS (1984): – HERMAN & ROFFWARG (1983): Discovered that after spending a day wearing distorting lenses, participants spent more time than usual in REM sleep – interpreted as the brain taking longer to organise all the new experiences. – The brain goes ‘off-line’ during REM sleep and tries to make sense of events that have recently occurred. Evaluating Reprogramming Theory + May explain why most dreams are inclusive of recent events, and why dreams tend not to make sense. + Can explain why old people spend less time in REM sleep. (As they will rarely be encountering new things for the first time) - Foetuses & very young infants spend very much time in REM sleep, though they very little if any memories processed which would require sorting out. Why do we dream? For AS you need to know 1 theory of sleep: • Reprogramming Theory ~~Further processing new information~~ [SORTED! – Hope this helped, I’m off to sleep now!] No pun intended, its 2:16am, really!