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How do psychologists define consciousness?

To be conscious is to be aware, but aware of what? Psychologists define consciousness as personal awareness of feelings, sensations, and thoughts. Driving through an unfamiliar city would provide ample opportunities to understand changes in our level of consciousness. You are aware of increased feelings of tension; you grip the steering wheel tightly. Your mouth has gone dry; beads of sweat cascade down your face. You see cars weaving in and out of traffic as if they were performing a high-speed ballet. You see a big truck in your rear-view mirror—or is it in your trunk? You start thinking that you shouldn’t be driving in this city during rush hour. Finally you reach the outskirts of the city and enter the suburbs. You see a snazzy sports car speed past you, and you picture yourself behind the wheel. Wait a minute! You just passed your exit!

As we noted in Chapter 1, William James described consciousness as a stream. Like a stream, consciousness is continuous, can change, and has depth. But the stream of consciousness is very personal; it is your own. Let’s return to your drive through an unfamiliar city. Throughout the drive, your awareness of external stimuli, such as other cars, and internal stimuli, such as the seat belt against your body, probably changed. Moreover, as you left the city, you daydreamed about a sports car. During this fantasy, your attention was directed inward and away from external sources of stimulation. To drive through the city, you had to focus your attention on the events around you; it was no time for consciousness to wander. But once you left the city, your attention could stray, and you missed your exit. We often engage in everyday behaviors without being completely aware of them; that is, they can occur outside of consciousness.

Psychologists have devised ingenious ways to investigate changes in our consciousness. For example, they have equipped people with beepers that sound at random intervals to signal them to report their thoughts in writing (Klinger, 1990). The advantage of this method is that it does not rely on memory.

These beepers are one of the methods used to study the change in consciousness that we call daydreaming. Almost all people daydream, although the frequency drops as we get older (Giambra, 1989). Most daydreams are spontaneous images or thoughts that pop into our mind for a brief time and are then forgotten. However, we can become adept at using daydreams to solve problems, to rehearse a sequence of events, or to find new or useful ideas. Some daydreams are deliberate attempts to deal with situations like a boring job by providing some internal stimulation. Nevertheless, the content of most daydreams is related to such everyday events as paying bills or selecting clothes to wear. About two -thirds of daydreams are related to the daydreamer’s immediate situation and tasks. Contrary to popular belief, daydreams about sex constitute a small proportion of all daydreams (Klinger, 1987). Nevertheless, approximately 95 percent of men and women report having had sexual daydreams at some time (Leitenberg & Henning, 1995).

The experience of daydreaming is different from normal waking consciousness, and for that reason it can be called an altered state of consciousness. However, our consciousness can change even more dramatically in the course of a day. The use of alcohol or other drugs often leads to major changes in consciousness and observable behavior. As we will see, some researchers consider hypnosis to be an altered state of consciousness. The rhythmic changes of sleeping and dreaming dramatically alter personal awareness. We will discuss the study of sleep and dreams as we investigate both consciousness and the biological rhythms of life.

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Circadian Rhythms

Biological changes that occur on a daily schedule are called circadian rhythms (circa, "about"; dies, "day"). Most of us have a single concentrated sleep period every 24 hours. The sleep-wake cycle is just one of our circadian rhythms; scientists can detect peaks and valleys in body temperature, heart rate, and hormone levels. For example, levels of the stress hormone cortisol are negligible an hour or two before sleep, begin increasing before we awaken, and reach a peak at or near awakening (Moore-Ede, Sulzman, & Fuller, 1982). Circadian rhythms are also important in detecting diseases and in planning drug treatments (Lamberg, 1989; Moore-Ede, Czeisler, & Richardson, 1983; Office of Technology Assessment, 1991). The results of medical tests can depend on when the test is given; drugs that help at one time of day may harm at another. The peak times for a number of indicators of health and disease are shown in Figure 6-1.

The Sleep-Wake Cycle. Chronobiology is the branch of science that investigates and applies information about biological rhythms. To determine what controls our biological rhythms, chronobiologists have observed volunteers who were isolated from all time cues-no watches, television, radio, or newspapers-in caves or special apartments. What happened in a world without time cues? If the volunteers typically went to sleep at midnight and awoke at 8 a.m., they began sleeping at 1 a.m. and awoke at 9 a.m. on the first day. On the next day they might begin their sleep another hour later (2 a.m.) and rise at about 10 a.m. Day by day their sleep cycle shifted later in the day, yet they maintained a systematic sleep-wake rhythm.

Why does our sleep-wake cycle shift? The answer lies in the suprachiasmatic nucleus (SCN), a pinhead-sized collection of neurons located in the hypothalamus (see Chapter2), just above the optic chiasm (Meijer & Rietveld, 1989). The SCN receives information about light and dark from the eyes and its own nerve pathways (Moore-Ede, 1993). The neurons of the SCN serve as an internal clock that exert indirect control over neurons throughout the body. Although this internal clock is accurate within a minute or two each day, it must be reset every day because it tends to run on a 25-hour cycle, not a 24 -hour, day (Moore-Ede, 1993).

Exactly how the biological clock operates is still under investigation. However, researchers suspect that the hormone melatonin, produced by the pineal gland, is involved. Bright light suppresses production of melatonin; darkness triggers secretion of the hormone. Because of its effects on our circadian rhythms, melatonin is sometimes referred to as "nature’s sleeping pill." Synthetic forms of it have been used to treat insomnia (Garfinkel et al., 1995), although more research needs to be done on the possible long-term effects of this treatment.

The 25-hour sleep-wake cycle in a laboratory is described as a free-running cycle because there are no external signals to reset the internal clock. Outside the laboratory, sunlight is the most important cue that resets the internal clock to a 24-hour day. However, meals, social interactions, and even alarm clocks also influence circadian rhythms (Moore-Ede, Sulzman, & Fuller, 1982).

Body Temperature. You might be surprised to find that your body temperature is not a constant 98.6 degrees; rather, it fluctuates 2 to 3 degrees over the course of a day (see Figure 6-2). The 24-hour (circadian) rhythm of body temperature is controlled by the SCN (Coleman, 1995). Body temperature is related to our level of alertness and our sleep-wake cycle. In fact, observations of circadian cycles in free-running situations show that sleep is associated more with our body temperature at bedtime than with the number of hours we have been awake (Czeisler et al., 1980). The sleep-wake and body temperature cycles are typically synchronized. However, when we are deprived of time cues or when we travel through time zones or change work shifts, these cycles can become uncoupled and cause problems such as fatigue and sleepiness.

High temperature typically corresponds to higher levels of alertness; low temperature generally corresponds to reduced alertness and motivation. Body temperature reaches its lowest point of the day during sleep; it then rises after we wake up and peaks in the afternoon. The body is primed for high levels of efficiency in the afternoon.

Have you heard the terms owls and larks applied to people with different sleep habits? Terms like these, as well as morning type and evening type (Smith, Reilly, & Midkiff, 1989), describe people who differ in the timing of their sleep-wake cycle and peak temperature. The peak temperature for a lark (morning type) is early in the day, around 8 a.m. An owl’s (evening type’s) temperature peaks later in the day, around 8 p.m. or later.

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Problems with Circadian Rhythms

Our 25-hour internal clock provides the flexibility needed to adjust to the seasons, with their accompanying changes in the number of hours of daylight. However, the modern era has stretched our body’s ability to adapt. For example, the ability to travel great distances through many time zones in very little time has given rise to the phenomenon known as jet lag.

Jet Lag. Hop on a jet in New York, and two hours later you can be in Chicago; the change of one time zone requires only a minor adjustment of your internal clock. A trip from New York to London takes about seven hours on a jet traveling through five time zones. You might be in London at 8 a.m., but your body thinks it’s the middle of the night (3 a.m. in New York). Your circadian rhythms are not synchronized with your surroundings; as a result, you are likely to experience the symptoms of jet lag: fatigue, difficulty concentrating, insomnia, and disturbed appetite.

Jet lag has little to do with the length of your flight; the key is the number of time zones you cross. Increase the number of time zones you cross, and you increase the need for adjustment. If you travel from New York to Lima, Peru--directly south through the same time zone—you do not need to reset your internal clock. But a trip from St. Louis to Hong Kong takes you through several time zones, requiring a major adjustment. The direction of travel influences the speed with which the body adapts. A westward trip—say from New York to Los Angeles—is equivalent to delaying your sleep by three hours and is called a phase delay. If you travel eastward from Los Angeles to New York, you shorten the day to 21 hours, which is known as a phase advance. Phase delays (east-west travel) coincide with the body’s tendency to extend the sleep-wake cycle to 25 hours. Therefore, it is easier to adapt to phase delays than to phase advances (west-east travel).

If you travel great distances and expect to experience jet lag, here is some advice. During short stays, eat and sleep on your home time so that you don’t need to reset your internal clock. For longer stays, start adjusting before you leave by eating meals according to the time of your destination. When you arrive at your destination, use the most powerful time cue—sunlight—to reset your internal clock to local time (Czeisler et al., 1986). However, the timing of your exposure to strong light is a key factor. The biological clock interprets exposure to bright light near the end of the usual sleep period (for example, 4 a.m.) as a dawn signal (a new day is starting) that can advance the clock and initiate a period of activity. By contrast, exposure to bright light near the end of the normal active period (awake hours) delays the clock and makes people want to go to sleep later than their normal time (Coleman, 1995).

Shift work often leads to a cumulative sleep loss. As many as 75 percent of night shift workers experience sleepiness on every night shift, and 20 percent report having fallen asleep on the job (Akerstedt, 1991). Charles Pollak, head of New York Hospital’s sleep clinic, says that the sleepiness resulting from shift rotation "doesn’t make it difficult to walk, see, or hear. But people who don’t get enough sleep can’t think, they can’t make appropriate judgments, [and] they can’t maintain long attention spans" (Toufexis, 1990, p. 78). The number of on-the-job errors peaks during the night shift, which can adversely affect work performance and even compromise public safety (Scott, 1994). The sleepiness resulting from shift work can interfere with a person’s ability to administer drugs to patients, to navigate a plane, or to operate a nuclear power plant. Sleepiness was a factor in serious accidents at two nuclear power plants (Chernobyl in the Ukraine and Three Mile Island in Pennsylvania) and the Exxon Valdez oil spill in Alaska. Moreover, an investigation of the 1986 explosion of the space shuttle Challenger cited errors in judgment that were related to sleep loss and shift work during the early morning hours (Report of the Presidential Commission on the Space Shuttle Challenger Accident, 1986). Sleep deprivation and sleep disorders contribute to accidents, reduced productivity, and higher medical costs (Fritz, 1993; National Commission on Sleep Disorders Research, 1992).

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