While we can now investigate sleep and related phenomena, not all researchers agree on exactly why we sleep. A number of different theories have been proposed to explain the necessity of sleep as well as the functions and purposes of sleep. The following are three of the major theories of sleep.
Repair and Restoration Theory of Sleep:According to the repair and restoration theory of sleep, sleeping is essential for revitalizing and restoring the physiological processes that keep the body and mind healthy and properly functioning. This theory suggests that NREM sleep is important for restoring physiological functions, while REM sleep is essential in restoring mental functions.
Support for this theory is provided by research that shows periods of REM sleep increase following periods of sleep deprivation and strenuous physical activity. During sleep, the body also increases its rate of cell division and protein synthesis, further suggesting that repair and restoration occurs during sleeping periods.
Evolutionary Theory of Sleep:Evolutionary theory, also known as the adaptive theory of sleep, suggests that periods of activity and inactivity evolved as a means of conserving energy. According to this theory, all species have adapted to sleep during periods of time when wakefulness would be the most hazardous.
Support for this theory comes from comparative research of different animal species. Animals that have few natural predators, such as bears and lions, often sleep between 12 to 15 hours each day. On the other hand, animals that have many natural predators have only short periods of sleep, usually getting no more than 4 or 5 hours of sleep each day.
Information Consolidation Theory of Sleep:The information consolidation theory of sleep is based on cognitive research and suggests that people sleep in order to process information that has been acquired during the day. In addition to processing information from the day prior, this theory also argues that sleep allows the brain to prepare for the day to come. Some research also suggests that sleep helps cement the things we have learned during the day into long-term memory. Support for this idea stems from a number of sleep deprivation studies demonstrating that a lack of sleep has a serious impact on the ability to recall and remember information.
Final Thoughts:While there is research and evidence to support each of these theories of sleep, there is still no clear-cut support for any one theory. It is also possible that each of these theories can be used to explain why we sleep. Sleeping impacts many physiological processes, so it is very possible that sleep occurs for many reasons and purposes.
Considered the father of psychoanalysis, Sigmund Freud (1856-1939) revolutionizes the study of dreams with his work The Interpretation Of Dreams.Freud begins to analyze dreams in order to understand aspects of personality as they relate to pathology. He believes that nothing you do occurs by chance; every action and thought is motivated by your unconscious at some level. In order to live in a civilized society, you have a tendency to hold back our urges and repress our impulses. However, these urges and impulses must be released in some way; they have a way of coming to the surface in disguised forms.
One way these urges and impulses are released is through your dreams. Because the content of the unconscious may be extremely disturbing or harmful, Freud believes that the unconscious expresses itself in a symbolic language.
Freud categorizes aspects of the mind into three parts:
Id - centered around primal impulses, pleasures, desires, unchecked urges and wish fulfillment.
Ego - concerned with the conscious, the rational, the moral and the self-aware aspect of the mind.
Superego - the censor for the id, which is also responsible for enforcing the moral codes of the ego.
When you are awake, the impulses and desires of the id are suppressed by the superego. Through dreams, you are able to get a glimpse into your unconscious or the id. Because your guards are down during the dream state, your unconscious has the opportunity to act out and express the hidden desires of the id. However, the desires of the id can, at times, be so disturbing and even psychologically harmful that a "censor" comes into play and translates the id's disturbing content into a more acceptable symbolic form. This helps to preserve sleep and prevent you from waking up shocked at the images. As a result, confusing and cryptic dream images occur.
According to Freud, the reason you struggle to remember your dreams, is because the superego is at work. It is doing its job by protecting the conscious mind from the disturbing images and desires conjured by the unconscious.