Discuss the nature of sleep, including two explanations of the functions of sleep

also be generalised to all babies as they all undergo large amounts of REM sleep. Most human growth hormone is released during the first stages of sleep; this supports the restoration theory as growth hormone is necessary for growth and repair, however despite a correlation we cannot imply cause and effect, that the burst of growth hormone is related to restoration functions in sleep. Another source of empirical evidence is that people who have damaged their brain in cases such as drug overdoses, spend longer in REM sleep which supports the theory that REM sleep is when the brain recovers and repairs, however we still cannot imply cause and effect that the increase in REM sleep is to repair the brain, it could be due to trauma, shock or damage a part of the brain that regulates sleep. A 1984 study showed that marine dolphins sleep with one hemisphere at a time which means they cannot undergo REM sleep which disproves the theory, however this study cannot be generalised to humans because it involves animals which have different physiological processes to humans.The restoration theory relies heavily on the biological approach which has empirical evidence to support this, but it does not explain any of the cognitive processes or how peoples experience’s affect sleep. It does not talk about the differences of sleep between cultures, but it is possible that there is no difference between cultures. It also shows that the nature of sleep is deterministic in the way that we can’t control our requirement of more or less sleep.The evolutionary theory of sleep states that the way we sleep is due to changes in our body so that we are best adapted to the environment. It refers back to prehistoric times when it was difficult to survive due to lack of food or threat of predation. Meddis suggested that one of the reasons why we sleep is for protection (predation theory) – at night, Humans are less adapted to survive due to poor light vision so sleeping keeps us safe. There are a few problems with this, for example Lions who have no natural predator sleep for long periods of time while herbivores who are at most risk sleep for short periods of time, however this cannot be generalised to humans because animals have different physiological processes. Bentley also suggested that if sleep is designed to make us inconspicuous then why do we snore, which disproves the predation theory. Webb came up with the idea that we conserve energy while we sleep due to a lower metabolic rate, but Meddis criticises this theory by stating that it is too simplistic and the amount of calories saved by sleeping compared to resting would be the same as a slice of bread. The evolutionary theory is backed up by plenty of evidence and is based on science, but we are unable to go back in time and find out what prehistoric life was like so this theory is based on assumptions, which also means cause and effect cannot be implied. The theory is also not reductionist because it thinks about multiple meanings of sleep. Evolutionary theories are unable to explain the complexities of sleep or why we can die from lack of sleep so it does not offer a full approach to the nature of sleep. We are now much more advanced, food is readily available and we are able to protect ourselves at night, so sleep would be pointless according to the evolutionary theory, however there is a possibility of the genome lag and that it would take a long time to adapt to our need for less sleep.