Individuals have a certain chronotype, which determines whether or not the person is a morning person or a night person. In some cases, the circadian rhythm gets disrupted, such as when experiencing jet lag after crossing several time zones. Individuals who do rotating shift work also have disruptions in their circadian rhythm and sleep-wake cycle. These individuals are at risk for anxiety and depression. The person who does not get enough sleep will exhibit a sleep debt, which can be chronic. Individuals with a sleep debt will have decreased alertness and lower mental efficiency. The fact that modern man has a great deal of exposure to artificial light sources has decreased the amount of sleep a person gets. If one sleeps less than 7 hours of sleep a night, there will be an accrual of sleep debt. People who can nap easily probably have a sleep debt. Newborns need the most amount of sleep at about 14 to 17 hours a day. This declines over time so that individuals who are teens between 14 and 17 years require between 8 and 10 hours of sleep per night. By aged sixty-five or older, only about 7 to 8 hours of sleep per night is the average. No one should get less than 5 hours of sleep per night. Lack of sleep also leads to symptoms of depression. It can happen with acute sleep deprivation or a more prolonged sleep debt. Lack of sleep is linked to obesity, increased stress hormones, high blood pressure, and a worsened immune system. These are people who can easily fall asleep behind the wheel because they are not moving much while driving.
HISTORY OF CONSCIOUSNESS The first records on consciousness come from the ancient Incas and Mayan people. They believed there were multiple levels of consciousness. They believed also that consciousness was the basic form of existence. The Incas believed that consciousness also meant having concern for others. There were early Western researchers on consciousness. John Locke believed that consciousness was linked to personal identity and that it can survive after the physical body died. Rene Descartes wondered why consciousness was linked to the physical
81
