human sleep

The great mystery of sleep in human experience is that we can know so little about an activity so intimate to us all. To put our familiarity with sleep into perspective, consider that we spend roughly a third of our lives sleeping—about eight hours’ sleep in every twenty-four-hour period. Sleep’s familiarity, however, paradoxically seems to blind us to its comprehensiveness. Many of us will be surprised, for example, to reflect that we spend as much time asleep each week as we do at our jobs. Similarly, when we view sleep in cumulative perspective, the lengths of time we log unconscious rapidly grow striking. Adult humans sleep between three and four months a year, while children and adolescents devote close to half of their young years to sleep. Over the course of a lifetime, by the time we have reached seventy years of age, each of us will have spent well over twenty years asleep. And curiously, five of those years will be spent dreaming.


Because dream sleep is the most unstable stage of sleep, due to all of the hallucinated activity that attends it, it is the time when we are most likely to spontaneously, or naturally, awaken. In fact, every morning, prior to our real or final awakening, we all awaken momentarily several times. Typically in a morning dream sleep period there are five or six of these tendencies toward waking. The dreamer may not even open his or her eyes, but on an EEG these “micro awakenings” are readily apparent. This is why when we awaken in the morning, we frequently are able to recall having just been dreaming. Our dreaming literally wakes us up. Because of this propensity to awaken from dream sleep, and because dream sleep always comes at the end of a ninety minute cycle, we tend to sleep in periods that are rough multiples of ninety minutes—most commonly four cycles, or 360 minutes (six hours), or five cycles, which is 450 minutes, or seven and a half hours. If you should awaken during the night and look at your clock, you will see that these ninety-minute cycles do indeed define our sleep periods; our awakenings from sleep are almost always in multiples of ninety minutes.

While there is a propensity for us to sleep in ninety-minute cycles, that is, to awaken at their completion and thus from dream sleep, there are many variables—alarm clocks, children, roommates, dogs, cats, street noises, needing to go to the bathroom—that cause us to awaken from all of the various stages of sleep. What has been demonstrated is that if we awaken from dream sleep, we most likely will recall having been dreaming, whereas if we awaken from any stage other than dream sleep, we most likely will not recall having been dreaming or, for that matter, having had any dreams during the night. Even when we do awaken directly from a dream, it can still be difficult to recall the dream in detail. Most dreams are lost by the time we get to the shower. 

©1995 Charles McPhee. Excerpted from Stop Sleeping Through Your Dreams: A Guide to Awakening Consciousness During Dream Sleep published by Henry Holt and Company, Inc.

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