Theories of Sleep (Recuperation vs. Circadian)

Why do we sleep? What governs when or how long we sleep? This activity will assist you in understanding two common sleep theories, recuperation and circadian, which provide different answers to these questions. Depending on which one you support, it may change your outlook on sleep and your current sleeping habits.

Categorize each characteristic under the correct theory—recuperation or circadian—by placing an “X” in the appropriate column. Then, answer the questions that follow.

  Recuperation Circadian
Sleep restores the body to a state of homeostasis. X  
Sleep plays no role in physiological functioning.   X
We become tired when it is dark out.   X
Function of sleep is to restore energy levels X  
Function of sleep is to conserve energy X  
We become tired from wakefulness. X  
We sleep until the body is physiologically sound. X  
We sleep based on an internal timing mechanism.   X
Sleep depends on vulnerability from predators.   X
Sleep deprivation may cause behavioral disturbances. X  
We have a sleep-wake cycle.   X
When we sleep is based on some evolutionary aspects.   X
  • What are the main differences between the recuperation and circadian theories?

The recuperation theory is based on the belief that the purpose of sleep is to bring the body back into homeostasis (Pinel, 2007). There are various theories as to how the body’s homeostasis is depleted, but all recuperation theories assert that sleep is brought on by a depletion of homeostasis. The overarching function of sleep, according to the recuperation theory, is to bring stability back to the body that is lost during waking hours.

The circadian theory of sleep maintains that sleep is an evolutionary advent that is used to avoid predation and conserve energy. According to this theory, sleep is brought on by internal timing mechanisms, which regulates how much sleep an organism requires. This theory maintains that the amount and number of sleep periods are governed by susceptibility to predation and the necessity to conserve energy.

  • Which theory do you most agree with? Explain.

I would probably agree the most with the circadian theory of sleep. I have personally seen the mechanisms of this theory in action. I have tried to work night jobs before. It never worked for me. I could only do it for about a week before mental exhaustion overtook me. I am not saying that our instinct to sleep during the dark hours cannot be overcome. My wife has worked nights for some time and it doesn’t phase her one bit. But personally, I have never been able to overcome my internal clock which dictates that when the sun goes down so do I, as it were. Also, I have worked at quite a few jobs requiring 10 or more hours of manual labor a day. I do not think that my long hours of sleep after days like that were caused because of a homeostatic imbalance. Quite the opposite, I think that I slept long hours in order to conserve energy so that long workdays such as those could be offset by long hours of energy conservation.


Pinel, J. P. J. (2007). Basics of biopsychology. Boston, MA: Allyn and Bacon.


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