A variation on Meddis is Webb’s (1974) Conservation Theory which also considers sleep to be an adaptive behaviour but this time in order to conserve energy. This theory compares sleep to hibernation as during hibernation, body temperature drops and the animal becomes inactive in order to conserve energy when food is scarce. Similarly to the ‘protection’ theory, this theory also states that the night time would have been an unproductive period for attaining food. Hence, humans tend to sleep at night to conserve resources by lowering the metabolic rate. It is also proposed that others factors affect sleep such as the higher the risk level from predators, the more the animal will sleep and the amount of time searching for food also effects the duration of an animal’s sleep time.
While on one hand, the hibernation theory is clearer and less ambiguous than the protection theory, it has still been subject to many criticisms. Meddis criticised this hibernation theory for being over-simplistic as according to Meddis, sleep has little to do with conserving energy but is rather a compromise between protection from danger and dietary requirements.
Empson (1993) described sleep as a very complex function of the brain that is more to do with the body and physiology than evolutionary history. Hence, the evolutionary theory in its entity fails to reflect the complexity of sleep, to explain why we have five stages of sleep and why we suffer psychological problems from sleep deprivation. It also does not consider the possibility of ‘snoring’ and although it has been noted that the evolution of biology and physiology takes hundreds of years- there is also the argument that according to this theory, sleep should now be pointless in human societies as we are more advanced and able to protect ourselves at night.
Another theory of sleep is the Restoration theory. Oswald (1966) put forward that sleep restores depleted sources of energy and removes waste from muscles while repairing cells e.g. during the day waste chemicals build up in the muscles following physical exertion and neurotransmitters are also likely to be used up as they are used for communication throughout the nervous system. Therefore, sleep may allow the body to remove this waste and replenish its levels of neurotransmitters in order to be prepared for activity the following day. The body could also repair the damaged cells during this time which is particularly beneficial for growth in the young.
Oswald proposed that there are two types of sleep; non REM sleep and REM sleep. Oswald claimed that NREM sleep is the time dedicated to replenishing and repairing the body. According to Oswald, stages 3 and 4 of sleep occur at the beginning of the night when the body is exhausted thus during these stages, our bodies secrete greater levels of growth hormone into the blood in order to facilitate the repair process which seems to offer support to this theory. It has been established that many restorative functions do indeed appear to occur while we sleep such as the process of digestion, protein synthesis and the removal of waste from muscles.
Shapiro (1981) provided further support for this theory as after studying ultra marathon runners who has completed a 57-mile run, it was found that they slept 90 minutes longer than usual for the next two nights. REM sleep decreased while stage 4 for NREM sleep increased markedly from 25% to 45%. This strongly indicates and demonstrates that extra sleep was needed to repair the extra activity that their bodies underwent.
REM sleep on the other hand was developed by Oswald (1980) and Hartman (1984) and is supposedly dedicated to restoring the brain. This theory was reinforced by Stern & Morgane (1974) who believed that neurotransmitter levels within the brain may be restored during SEM sleep. More sleep is needed for younger children and babies as their brain is growing and developing at its fastest rate. A newborn spends 9 hours a day in REM compared to 2 hours in adults.
The restoration theory seems to make a lot of sense, particularly considering that we do indeed feel more refreshed after a healthy amount of sleep. Many researches support this theory as it has been shown that the disruption of stage 4 sleep can cause fibrositis which is a condition of the lower back caused by muscle wasting and it has also been proven that we secrete a growth hormone essential for protein synthesis in our sleep. This scientific and objective evidence greatly emphasises and provides support for Oswald’s theories of sleep. Further evidence also provides additional support for the restoration theory such as; the way patients who have suffered a brain insult will spend longer in REM for an average of 6 weeks and how babies sleep for much longer than adults as these pieces of information indicate that REM sleep is spent repairing our bodies and helping young brains to develop.
Conversely, there is also much evidence to dispute this theory. It has been pointed out that protein synthesis occurs 24 hours a day, not just during stage 4 which may disprove Oswald’s theory but nonetheless, evidence has shown that protein synthesis does seem to peak at stage 4. Ryback & Lewis also proved that sleep doesn’t seem to decrease when our level of daytime activity decreases and Horne & Millar (1985) found that we fall asleep earlier following physical exertion but we do not necessarily sleep for longer – this may contradicts the restoration theory’s claim that sleep restores the damage done to our body in the day. It is also argued that the processes that occur during sleep also occur while we’re awake too which therefore reveals why the restoration theory is often considered over simplistic, especially considering the fact that neuro-chemicals appear to be produced throughout a night’s sleep and not just during REM.
Furthermore, in regards to animal studies; the restoration theory claims that more active species will sleep for longer. Though, the sloth is one of the least active creatures but sleeps for 20 hours a day whereas some very active humans get by on just a few hours of sleep.
However, Horne (1988) extends Oswald’s theory by suggesting that sleep is actually divided into core sleep (REM) and optional seep (SWS). He suggested that brain restoration and repair takes place during core sleep and body restoration occurs during optional sleep but can also occur at other times. This is an improvement as it tries to address the argument that body restoration also occurs when we are awake.
Sleep deprivation studies provide evidence for the restoration theory too. Pete Tripp, for example, attempted to stay awake for eight days in Jan 1959. Two psychologists joined in the study in order to help him stay awake. Findings showed that initially Tripp was very upbeat and alert but it gradually became increasingly difficult for him to stay awake. After 2-3 days, Tripp became very abusive towards those around him. Daily medical examinations showed that physical changes like a dramatic drop in body temperature took place and in turn this caused his behaviour to decline. By day 5, he was hallucinating. Peter Tripp achieved his goal of no sleep for 201 hours and when he finally went to sleep, he slept for 24 hours and returned back to normal.
In one way Peter Tripp’s experiment can support the restoration theory as it he did sleep for longer than usual and he did start hallucinating which indicates that his brain was overworked as it had no time to replenish itself. It also showed the detrimental effect not sleeping can have on the body- both psychologically and physically. However, his experiment also goes against the restoration theory of sleep as even after 201 hours of not sleeping, Tripp only slept for 24 hours. He did not make up for all the hours of sleep he missed indicating that perhaps the amount of sleep we need is not entirely dependent on the amount of activity done in the day.
There are also certain methodological and ethical issues involved in this study. Tripp’s experiment was undertaken in a controlled environment and involved the use of drugs and help of other people to keep him awake therefore the findings are not ecologically valid as it is not reflective of real life situation. This could be an advantage though in certain respects as the controlled conditions allow for a clear cause and effect relationship to be identified. Moreover, the study was a case study which on one had is a strength as it would prompt rich, qualitative data but it is also a weakness as its idiographic so only focuses on the individual at hand- preventing it from being generalised to the wider population. In regards to ethnical issues, protection from harm is a big problem in this study as Tripp suffered many distressing side effects such as hallucinations.
Randy Gardner (1965) also deprived himself of sleep by staying awake for eleven nights for a school science project. He reported blurred vision, slurred speech and mild paranoia. When Randy did sleep, he slept for 14 hours and 14 minutes the first night and two hours longer than usual on the next two nights. Despite losing 90 hours of sleep, he only made up for 11 hours. Nevertheless, he caught up on a disproportionate amount of his lost stage 4 and REM sleep suggesting they are vital stages. Again, it is difficult to generalise these case studies to the wider population due to the very small sample size.
Human sleep deprivation studies do appear to support the restoration theory and they have emphasised how total sleep deprivation is fatal showing that it is an absolute necessity for us. However, sleep deprivation theories can often be very artificial which creates the issue of mundane realism. It has also be argued in these studies, the stress could result in the side effects instead – especially as the participant is usually very closely monitored and observed.
