Consciousness is our awareness of ourselves and our environment (Paller & Suzuki, 2014). Consciousness enables us to exert voluntary control and to communicate our mental states to others. When we learn a complex concept or behavior, it is consciousness that focuses our attention. It lets us assemble information from many sources as we reflect on the past, adapt to the present, and plan for the future.

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Can consciousness persist in a permanently motionless body? Possibly, depending on the underlying condition. A hospitalized 23-year-old woman showed no outward signs of conscious awareness (Owen, 2014; Owen et al., 2006). But when researchers asked her to imagine playing tennis, fMRI scans revealed activity in a brain area that normally controls arm and leg movements. Even in a motionless body, the researchers concluded, the brain—and the mind—may still be active (FIGURE 2.25).

Consciousness is not located in any one small brain area. Conscious awareness is a product of coordinated, brain-wide activity (Chennu et al., 2014; Gaillard et al., 2009; Schurger et al., 2010). In a brain scan, your awareness of a loved one’s presence would appear as a pattern of strong signals bouncing back and forth among many brain areas (Blanke, 2012; Boly et al., 2011; Olivé et al., 2015). Our brain is a whole system, and our mental experiences arise from coordinated brain activity.

When we consciously focus on a new or complex task, our brain uses sequential processing, giving full attention to one thing at a time. But sequential processing is only one track in the two-track mind. Even while your conscious awareness is intensely focused elsewhere, your mind’s other track is taking care of routine business (breathing and heart function, body balance, and hundreds of other tasks) by means of parallel processing. Some “80 to 90 percent of what we do is unconscious,” says Nobel Laureate and memory expert Eric Kandel (2008).

In addition to normal waking awareness, consciousness comes to us in altered states, aspects of which are discussed in other chapters—hypnosis in Chapter 5, for example, and consciousness-altering drugs in Chapter 13. Here we take a close look at the role of attention, and two altered states we all experience—sleep and dreams.

Your conscious awareness focuses, like a flashlight beam, on a very small part of all that you experience. Psychologists call this selective attention. Until reading this sentence, you were unaware that your nose is jutting into your line of vision. Now, suddenly, the spotlight shifts, and your nose stubbornly intrudes on the words before you. While focusing on these words, you’ve also been blocking other parts of your environment from awareness, though your normal side vision would let you see them easily. You can change that. As you stare at the X below, notice what surrounds these sentences (the edges of the page, the desktop, the floor).

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X

Chat on your phone, text, or tweak your playlist while driving, and your selective attention will shift back and forth between the road and its electronic competition. Indeed, it shifts more than we realize. One study left people in a room for 28 minutes, free to surf the Internet and to control and watch a TV. How many times did their attention shift between the two? Participants guessed it was about 15 times. Not even close! The actual number (verified by eye-tracking equipment) was 120 (Brasel & Gips, 2011).

Rapid toggling between activities is today’s great enemy of sustained, focused attention. When we switch attentional gears, especially when we shift complex tasks like noticing and avoiding cars around us, we pay a toll—a slight and sometimes fatal delay in coping (Rubenstein et al., 2001).

When a driver attends to a conversation, activity in brain areas vital to driving decreases an average of 37 percent (Just et al., 2008). Chatting or texting—something 1 in 4 drivers admits doing—has been present in about 28 percent of traffic accidents (NSC, 2010; Pew, 2011). One video cam study of teen drivers found that driver distraction from passengers or phones occurred just before 58 percent of their crashes (AAA, 2015). Phone use is the bigger distraction. Talking with passengers raises the risk of an accident 1.6 above normal. Using a cell phone (even a hands-free set) carries a risk 4 times higher than normal—equal to the risk of drunk driving (McEvoy et al., 2005, 2007).

Talking is distracting, but texting wins the danger game. In an 18-month video cam study that tracked the driving habits of long-haul truckers, their risk of a collision was 23 times greater when they were texting (Olson et al., 2009). Mindful of such findings, most U.S. states now ban texting while driving.

Our conscious attention is so powerfully selective that we become “blind” to all but a tiny sliver of the immense ocean of visual stimuli constantly before us. In one famous study, people watched a one-minute video of basketball players, three in black shirts and three in white shirts, tossing a ball (Becklen & Cervone, 1983; Neisser, 1979). Researchers told the viewers to press a key each time they saw a black-shirted player pass the ball. Most viewers were so intent on their task that they failed to notice a young woman carrying an umbrella stroll across the screen midway through the clip (FIGURE 2.26). During a replay, they were amazed to see her! With their attention focused elsewhere, the viewers suffered from inattentional blindness. In another study, two smart-aleck researchers had a gorilla-suited assistant thump his chest and move through the swirl of players. Did he steal the show? No—half the pass-counting viewers failed to see him, too (Simons & Chabris, 1999).

The invisible gorilla struck again in a study of 24 radiologists who were asked to search for signs of cancer in lung scans. All but 4 of them missed the little image of a gorilla embedded in the scan (Drew et al., 2013). They did, however, spot the much tinier groups of cancer cells, which were the focus of their attention.

Given that most of us miss people strolling by in gorilla suits while our attention is focused elsewhere, imagine the fun that others can have by distracting us. Misdirect our attention and we will miss the hand slipping into the pocket. “Every time you perform a magic trick, you’re engaging in experimental psychology,” says magician Teller, a master of mind-messing methods (2009). Clever thieves know this, too. One psychologist was surprised by a woman exposing herself. Only later did he realize her crime partner had picked his pocket (Gallace, 2012).

Magicians also exploit our change blindness (a form of inattentional blindness). With a dramatic flourish, they direct our selective attention away from other changes being made. So, too, in laboratory experiments, where viewers failed to notice that, after a brief visual interruption, a big Coke bottle had disappeared, a railing had risen, clothing had changed color—and construction workers had changed places (FIGURE 2.27) (Chabris & Simons, 2010; Resnick et al., 1997). Out of sight, out of mind.

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The point to remember: Our conscious mind is in one place at a time. But outside our conscious awareness, the other track of our two-track mind remains active—even during sleep, as we see next.

Each night, we lose consciousness and slip into sleep. We may feel “dead to the world,” but we are not. Our perceptual window remains open a crack, and our two-track mind continues to process information outside our conscious awareness. We move around on the bed but manage not to fall out. And if someone speaks our name, our unconscious body will perk up. Although the roar of my [ND’s] neighborhood garbage truck leaves me undisturbed, my baby’s cry will shatter my sleep. Our auditory cortex responds to sound stimuli during sleep (Kutas, 1990).

Sleep’s mysteries puzzled scientists for centuries. Now, in laboratories around the world, some of these mysteries are being solved as people sleep, attached to recording devices, while others observe. By recording brain waves and muscle movements, and by watching and sometimes waking sleepers, researchers are glimpsing things that a thousand years of common sense never told us.

Biological Rhythms and Sleep

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Like the ocean, life has its rhythmic tides. Let’s look more closely at two of these biological rhythms—our 24-hour biological clock and our 90-minute sleep cycle.

CIRCADIAN RHYTHM Try pulling an all-nighter, or working an occasional night shift. You’ll feel groggiest in the middle of the night but may gain new energy when your normal wake-up time arrives. This happens thanks to your body’s internal biological clock, its circadian rhythm (from the Latin circa, “about,” and diem, “day”). Your wake-up call is a sign that your internal clock is doing its job—keeping you roughly in tune with the 24-hour cycle of day and night. As morning approaches, body temperature rises. Then it peaks during the day, dips for a time in early afternoon (when many people take naps), and begins to drop again in the evening. Thinking is sharpest and memory most accurate when we are at our daily peak in circadian arousal.

Age and experience can alter our circadian rhythm. Most 20-year-olds are evening-energized “owls,” with performance improving across the day (May & Hasher, 1998). After age 20, our clocks begin to shift. Most older adults are morning-loving “larks,” with performance declining as the day wears on (Roenneberg et al., 2004). Women, if they have children, but also as they go through menopause, morph into larks slightly earlier than men (Leonhard & Randler, 2009; Randler & Bausback, 2010). Most retirement homes are quiet by mid-evening, when the night has hardly begun for many young adults.

SLEEP STAGES Sooner or later, sleep overtakes us all, and consciousness fades as different parts of our brain’s cortex stop communicating (Massimini et al., 2005). Yet the sleeping brain is active and has its own biological rhythm. About every 90 minutes, we cycle through distinct sleep stages. This basic fact came to light after 8-year-old Armond Aserinsky went to bed one night in 1952. His father, Eugene, needed to test an electroencephalograph he had repaired that day (Aserinsky, 1988; Seligman & Yellen, 1987). Placing electrodes near Armond’s eyes to record the rolling eye movements then believed to occur during sleep, Aserinsky watched the machine go wild, tracing deep zigzags on the graph paper. Could the machine still be broken? As the night proceeded and the activity recurred, Aserinsky realized that the periods of fast, jerky eye movements were accompanied by energetic brain activity. Awakened during one such episode, Armond reported having a dream. Aserinsky had discovered what we now know as REM sleep (rapid eye movement sleep).

Similar procedures used with thousands of volunteers showed the cycles were a normal part of sleep (Kleitman, 1960). To appreciate these studies, imagine yourself as a participant. As the hour grows late, you feel sleepy and get ready for bed. A researcher comes in and tapes electrodes to your scalp (to detect your brain waves), on your chin (to detect muscle tension), and just outside the corners of your eyes (to detect eye movements) (FIGURE 2.28). Other devices will record your heart rate, breathing rate, and genital arousal.

When you are in bed with your eyes closed, the researcher in the next room sees on the EEG the relatively slow alpha waves of your awake but relaxed state (FIGURE 2.29). As you adapt to all this equipment, you grow tired. Then, in a moment you won’t remember, your breathing slows and you slip into sleep. The EEG now shows the irregular brain waves of the non-REM sleep stage called NREM-1 sleep (Silber et al., 2008).

During this brief NREM-1 sleep you may experience fantastic images resembling hallucinations. You may have a sensation of falling (at which moment your body may suddenly jerk) or of floating weightlessly. These are hypnagogic sensations (from the Greek root words meaning “leading to sleep”). Your brain may later treat them as real memories. People who claim they were abducted by aliens—often shortly after getting into bed—commonly recall being floated off from (or pinned down on) their beds (Clancy, 2005).

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You then relax more deeply and begin about 20 minutes of NREM-2 sleep. The EEG will show bursts of rapid, rhythmic brain-wave activity. Although you could still be awakened without too much difficulty, you are now clearly asleep.

Then you enter the deep sleep of NREM-3. During this slow-wave sleep, which lasts for about 30 minutes, your brain emits large, slow delta waves. You would be hard to awaken. (It is at the end of this stage that children may wet the bed.)

REM SLEEP About an hour after you first dive into sleep, a strange thing happens. You reverse course. From NREM-3, you head back through NREM-2 (where you’ll ultimately spend about half your night). You then enter the most puzzling sleep phase—REM sleep (FIGURE 2.30). And the show begins. For about 10 minutes, your brain waves become rapid and saw-toothed, more like those of the nearly awake NREM-1 sleep. But unlike NREM-1, during REM sleep your heart rate rises and your breathing becomes rapid and irregular. Every half-minute or so, your eyes dart around in a brief burst of activity behind your closed lids. These eye movements announce the beginning of a dream—often emotional, usually story-like, and richly hallucinatory.

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Except during very scary dreams, your genitals become aroused during REM sleep. You have an erection or increased vaginal lubrication and clitoral engorgement, regardless of whether the dream’s content is sexual (Karacan et al., 1966). Men’s common “morning erection” stems from the night’s last REM period, often just before waking. (Many men who have occasional erectile problems get sleep-related erections, suggesting the problem is not between their legs.)

During REM sleep, your brain’s motor cortex is active but your brainstem blocks its messages. This leaves your muscles relaxed, so much so that, except for an occasional finger, toe, or facial twitch, you are essentially paralyzed. Moreover, you cannot easily be awakened. REM sleep is thus sometimes called paradoxical sleep. The body is internally aroused, with waking-like brain activity, but externally calm—except for those darting eyes

As the night goes on, the 90-minute sleep cycle repeats itself over and over—with one difference. Deep NREM-3 sleep grows shorter and disappears, and REM and NREM-2 sleep periods get longer (see FIGURE 2.30). By morning, we have spent 20 to 25 percent of an average night’s sleep—some 100 minutes—in REM sleep. In sleep lab studies, 37 percent of participants have reported rarely or never having dreams “that you can remember the next morning” (Moore, 2004). Yet even they, more than 80 percent of the time, could recall a dream if awakened during REM sleep. Each year, we spend about 600 hours experiencing some 1500 dreams. Over a typical lifetime, this adds up to more than 100,000 dreams—all swallowed by the night but not acted out, thanks to REM’s protective paralysis.

Why Do We Sleep?

True or false? “Everyone needs 8 hours of sleep.” False. The first clue to how much sleep a person needs is their age. Newborns often sleep two-thirds of their day, most adults no more than one-third. But there is more to our sleep differences than age.

Some adults thrive on fewer than 6 hours a night. Others regularly rack up 9 hours or more. Some of us are awake between nightly sleep periods, breaking the night into a “first sleep” and a “second sleep” (Randall, 2012). And for those who can nap, a 15-minute midday snooze can be as effective as an additional hour at night (Horne, 2011). Heredity influences sleep patterns, and researchers are tracking the sleep-regulating genes in humans and other animals (Donlea et al., 2009; Hor & Tafti, 2009; Mackenzie et al., 2015).

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But let’s not forget another of this book’s Big Ideas: Biological, psychological, and social-cultural influences interact. We can see this interaction in sleep patterns. Thanks to modern lighting, shift work, and social media diversions, many who would have gone to bed at 9:00 P.M. a century ago are now up until 11:00 P.M. or later. Those extra hours awake are often subtracted from sleep time. In Britain, Canada, Germany, Japan, and the United States, adults average 6½ to 7 hours of sleep a night on workdays, and 7 to 8 hours on other days (National Sleep Foundation, 2013).

Whether for work or play, bright light can disrupt our biological clock, tricking the brain into thinking night is morning. The process begins in our eyes’ retinas, which contain light-sensitive proteins. Bright light sets off an internal alarm by activating these proteins, which then signal a brain structure called the suprachiasmatic nucleus (FIGURE 2.31). This brain structure in turn decreases production of the sleep-inducing hormone melatonin (Chang et al., 2015; Gandhi et al., 2015). This process can put sports teams at a disadvantage. One study of more than 24,000 Major League Baseball games found that teams who had crossed three time zones before playing a series had nearly a 60 percent chance of losing their first game (Winter et al., 2009).

SLEEP THEORIES So our sleep patterns differ from person to person and from culture to culture. But why do we need to sleep? Psychologists offer five possible reasons.

Given all the benefits of sleep, it’s no wonder that sleep loss—our next topic of discussion—hits us so hard.

Sleep Deprivation and Sleep Disorders

Sleep commands roughly one-third of our lives—some 25 years, on average. With enough sleep, we awaken refreshed and in a better mood. We work more efficiently and accurately. But when our body yearns for sleep and does not get it, we feel terrible. Trying to stay awake, we will eventually lose. In the tiredness battle, sleep always wins.

THE EFFECTS OF SLEEP LOSS Today, more than ever, our sleep patterns leave us not only sleepy but drained of energy and feelings of well-being. This tiredness tendency has grown so steadily that some researchers have labeled current times as the “Great Sleep Recession” (Keyes et al., 2015). After a series of 5-hour nights, we run up a sleep debt that won’t be wiped out by one long snooze. “The brain keeps an accurate count of sleep debt for at least two weeks,” reported sleep researcher William Dement (1999, p. 64).

College students are especially sleep deprived. In one national survey, 69 percent reported “feeling tired” or “having little energy” on at least several days in the two previous weeks (AP, 2009). Small wonder so many fall asleep in class. The going needn’t get boring for students to start snoring.

Sleep loss also affects our mood. Tired often equals crabby—less sleep predicts more conflicts in students’ friendships and romantic relationships (Gordon & Chen, 2014; Tavernier & Willoughby, 2014). Sleep loss can also predict depression, as one study of 15,500 young people, ages 12 to 18, showed. Risk of depression was 71 percent higher for teens who slept 5 or fewer hours a night, compared with those who slept 8 hours or more (Gangwisch et al., 2010). The link does not reflect an effect of depression on sleep. In long-term studies, sleep loss predicts depression, not vice versa (Gregory et al., 2009). REM sleep’s processing of emotional experiences helps protect against depression (Walker & van der Helm, 2009). After a good night’s sleep, we often do feel better the next day.

Chronic sleep loss can suppress the immune system, lowering our resistance to illness. With fewer immune cells, we are less able to battle viral infections and cancer (Möller-Levet et al., 2013; Motivala & Irwin, 2007). One experiment exposed volunteers to a cold virus. Those who had been averaging less than 7 hours of sleep a night were three times more likely to develop the cold than were those sleeping 8 or more hours a night (Cohen et al., 2009). Sleep’s protective effect may help explain why people who sleep 7 to 8 hours a night tend to outlive their sleep-deprived agemates (Dew et al., 2003; Parthasarathy et al., 2015).

When sleepy frontal lobes confront visual attention tasks, reactions slow and errors increase (Caldwell, 2012; Lim & Dinges, 2010). For drivers in an unexpected situation, slow responses can spell disaster. Drowsy driving has contributed to an estimated one of six deadly American traffic accidents (AAA, 2010). One 2-year study examined the driving accident rates of more than 20,000 Virginia 16- to 18-year-olds in two major cities. In one city, the high schools started 75 to 80 minutes later than in the other. The late starters had about 25 percent fewer crashes (Vorona et al., 2011).

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Deliberate manipulation of driver fatigue on the road would be illegal and unethical. But twice each year, most North Americans participate in a revealing sleep-manipulation experiment: We “spring forward” to daylight savings time and “fall back” to standard time. A search of millions of Canadian and U.S. records showed that accidents increased immediately after the spring-forward change, which shortens sleep (Coren, 1996) (FIGURE 2.33). The same spring-forward effect appeared in another study, which showed that tired people are more likely to “cyberloaf”—to fritter away time online. On the Monday after daylight savings time begins, entertainment-related Google searches have been 3.1 percent higher than on the preceding Monday, and 6.4 percent higher than on the following Monday (Wagner et al., 2012).

So sleep loss can destroy our mood, lower our resistance to infection, and decrease driver safety. It can also make us gain weight. Children and adults who sleep less than normal are heavier than average. And in recent decades, people have been sleeping less and weighing more (Shiromani et al., 2012). Here’s how it happens. Sleep deprivation

These effects may help explain the weight gain common among sleep-deprived college students.

FIGURE 2.34 summarizes the effects of sleep deprivation. But there is good news! Psychologists have discovered a treatment that strengthens memory, increases concentration, boosts mood, moderates hunger, reduces obesity, fortifies the disease-fighting immune system, and lessens the risk of fatal accidents. Even better news: The treatment feels good, it can be self-administered, the supplies are limitless, and it’s free! If you are a typical college-age student, often going to bed near 2:00 A.M. and dragged out of bed 6 hours later by the dreaded alarm, the treatment is simple: Add 15 minutes to your sleep each night until you feel more like a rested and energized student and less like a zombie. For some additional tips on getting better quality sleep, see TABLE 2.2.

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MAJOR SLEEP DISORDERS Do you have trouble sleeping when anxious or excited? Most of us do. (Warning: A smart phone tucked under your pillow as an alarm clock increases the likelihood that you’ll have a bad night’s sleep.) An occasional loss of sleep is nothing to worry about. But for those who have a major sleep disorder—insomnia, narcolepsy, sleep apnea, sleepwalking, sleeptalking, or night terrors—trying to sleep can be a nightmare. (See TABLE 2.3 for a summary of these disorders.)

Dreams

Now playing at an inner theater near you: the premiere showing of a sleeping person’s dream. This never-before-seen mental movie features engaging characters wrapped in a plot that is original and unlikely, yet seemingly real.

REM dreams are vivid, emotional, and often bizarre (Loftus & Ketcham, 1994). Waking from one, we may wonder how our brain can so creatively, colorfully, and completely construct this inner world. Caught for a moment between our dreaming and waking consciousness, we may even be unsure which world is real. A 4-year-old may awaken and scream for his parents, terrified of the bear in the house.

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Each of us spends about six years of our life in dreams—adventures that remain locked behind our moving eyelids and usually vanish with the new day. The discovery of the link between REM sleep and dreaming gave us a key to that lock. Now, instead of relying on a dreamer’s hazy recall hours or days after waking, researchers can catch dreams as they happen. They can awaken people during or within 3 minutes after a REM sleep period and hear a vivid account.

WHAT WE DREAM Few REM dreams are sweet. For both women and men, 8 in 10 are bad dreams (Domhoff, 2007). Common themes are failing in an attempt to do something; being attacked, pursued, or rejected; or experiencing misfortune (Hall et al., 1982). Dreams with sexual imagery occur less often than you might think. In one study, only 1 in 10 dreams among young men and 1 in 30 among young women had sexual overtones (Domhoff, 1996). More commonly, our dreams feature people and places from the day’s nonsexual experiences (De Koninck, 2000).

Our two-track mind continues to monitor our environment while we sleep. Sensory stimuli—a particular odor or a phone’s ringing—may be instantly woven into the dream story. In a classic experiment, researchers lightly sprayed cold water on dreamers’ faces (Dement & Wolpert, 1958). Compared with sleepers who did not get the cold-water treatment, these people were more likely to dream about a waterfall, a leaky roof, or even about being sprayed by someone.

WHY WE DREAM Dream theorists have proposed several explanations of why we dream, including these five:

Despite their differences, today’s dream researchers agree on one thing: We need REM sleep. Deprived of it in sleep labs or in real life, people return more and more quickly to the REM stage when finally allowed to sleep undisturbed. They literally sleep like babies—with increased REM sleep, known as REM rebound. Withdrawing REM-suppressing sleeping pills also increases REM sleep, often with nightmares.

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We have glimpsed the truth of this chapter’s overriding principle: Biological and psychological explanations of behavior are partners, not competitors. We are privileged to live in a time of breathtaking discovery about the interplay of our biology and our behavior and mental processes. Yet what is unknown still dwarfs what is known. We can describe the brain. We can learn the functions of its parts. We can study how the parts communicate. We can observe sleeping and waking brains. But how do we get mind out of meat? How does the electrochemical whir in a hunk of tissue the size of a head of lettuce give rise to a feeling of joy, a creative idea, or a crazy dream?

The mind seeking to understand the brain—that is indeed among the ultimate scientific challenges. And so it will always be. To paraphrase scientist John Barrow, a brain simple enough to be understood is too simple to produce a mind able to understand it.