Before we can consider different states of consciousnessconsciousnessOur awareness of ourselves and our environment — exists on a continuum from full alertness to deep unconsciousness., we have to attempt an answer to a rather prickly question – What is consciousness? As we consider this question, we'll see a number of problems with even attempting to come up with answers.

In chapter 1 we looked at Descartes' notion that the mind and body were separate entities. Descartes suggested that the non-material mind controlled the material body via the pineal gland, but as we'll see later in this chapter, the pineal gland is now known to serve other functions.

We may admit, however, that the mind does feel separate from the body. When we imagine ourselves looking out into the world, we may have a tendency to think in terms of the Cartesian Theater. This is the feeling that the mind is like a person inside of the head looking out at the world and controlling the body. This little person in the head doesn't really exist, of course, and if it were to exist, we would have to wonder what was inside of the head of that person inside the head, ad infinitum. This difficulty in understanding the relationship between the mind and the body is known as the mind-body problem of consciousness.

If I begin by at least accepting the notion that I'm conscious, how do I know that you are conscious? How can I be sure that I am not the only conscious one? In imagining a world in which no one else is actually conscious, you may realize that it might not be all that different from the world you currently experience. People move around, talk, and go to work and school, but what if they were all just automatons? What if they were just mindless zombies going about tasks with no internal mental experience at all? Sure, they could tell you they have internal experiences, but how could you be certain that their words weren't just for show, a clever ruse to throw you off track?

Certainly I could program a computer to say things that would make it sound like the computer has internal experience, but that wouldn't mean that it feels like something to be that computer. It seems that we naturally assume that other humans all have an internal mental experience, but can we ever really know?

This problem of other minds may make us wonder about the experience of other non-human organisms as well. In a famous essay, “What is it like to be a bat?” philosopher Thomas Nagel pondered this question. When we observe a bat's behavior, we might think there is “something it is like to be that organism” and then wonder what that something is actually like.

Nagel theorized, however, that it would be impossible for us to ever truly understand the experience of being a bat, because we are trapped in the viewpoint of being human. Nagel wrote that when he considers the experience of being a bat, “it tells me only what it would be like for me to behave as a bat does”. Our assumptions and expectations of what it's like to be another animal probably reveal more about what it's like to be a human. So when you try to see the world through your dog's eyes, you reveal how you think dogs experience the world, which may not represent how dogs actually experience it. In attempting to imagine the experience of other minds, we cannot escape the experience of our own minds.

Perhaps even our tendency to imagine that others have internal mental experience is unique to our human minds. We seem to automatically assume internal intentions, characteristics, and traits simply by observing behavior. We do this when we observe other humans (which is why movies are more engrossing than just patterns of light on a screen) and also when we observe other animals and even objects. This was demonstrated in a classic study by Fritz Heider and Marianne Simmel in which participants observed a brief animation of two circles and a triangle moving around a square. After viewing the video, participants felt that the shapes had distinct personalities, motivations, and emotions. While this film certainly wouldn't win any Academy Awards, it demonstrates our human tendency to assume internal experience based solely on observation of behavior.

In considering the consciousness of others, we might think of being conscious as being able to react to stimuli in the environment. This can be referred to as minimal consciousness. Of course, this minimal consciousness doesn't necessarily imply an experience of being that organism. Plants respond to light in their environment (and many even move toward it) but we may still doubt whether it feels like something to be a tree or a vine. On the other end of the spectrum, we might consider the rich and varied experience of full human consciousness, which includes responding to our environment as well as our own internal thoughts.

Part of the richness of this experience includes the ability to be aware of our own conscious processes and reflect on our own experience, known as self-consciousness. In this way, we're able to make ourselves the object of our conscious focus (rather than just being the subject that is experiencing consciousness). We can consider how others view us and even reflect on our own thoughts and reflections.

Speaking of reflecting, one way of attempting to determine whether other animals have a sense of self-awareness is the mark test used by Gordon Gallup in 1970. After giving chimps some experience with mirrors, Gallup secretly placed a spot of dye on their faces, then had those chimps interact with a mirror again. If, upon seeing the spot, they reached toward their own faces, Gallup believed this indicated that they understood how mirrors worked and could view themselves as objects.

Other research has indicated that human children are able to pass this test by the age of about 18 months. This test has been repeated in a number of animal designs, revealing that humans are in select company when it comes to being able to recognize ourselves in mirrors. Other primates like chimps and orangutans are able to pass the test (along with elephants, dolphins, and perhaps some bird species) while most other animals fail. This may not come as a surprise to dog or cat owners who see their pets repeatedly flummoxed by mirrors, never learning that they are looking at their own reflections.

Of course, while it's certainly interesting to consider which animals seem to be able to recognize themselves, we still can't be sure that passing this test really reflects some special type of self-awareness.

Even if I put aside the possibility that everyone else is a philosophical zombie and instead I assume that they do indeed have conscious experience, one large problem remains. If we aren't all zombies, why not? Why aren't we simply automatons? Why is there a subjective component to our experiences? And if we adopt a monist approach, how is it that this subjective experience arises from physical processes in the brain? This is known as the hard problem of consciousness. And given just how hard a problem it is, we don't quite have a good answer for it. We may assume that there must be some sort of evolutionary advantages to developing consciousness, but it's hard to say for sure why those advantages couldn't arise in non-conscious zombies who were simply programmed to behave as we do.

Information in our minds may fall into a number of different categories of consciousness, depending on our level of access to the information. The conscious level contains information that we are presently aware of. This would include all the thoughts and sensations that we are currently thinking about. Thoughts that aren't in our conscious mind at the moment but can be brought into consciousness rather easily are considered to be at the preconscious level.

The subconscious level consists of influences and mental processes that we are generally unaware of, though we can see their effects on our behavior. We may not be aware of these in the moment, but we can clearly see how they have influenced behavior after the fact. This level would also include the subtle influence of priming and mere-exposure effects, which will be discussed later in this chapter (you can remember subtle and subconscious).

Things can get murky here because these subconscious influences are frequently described using the term unconscious, though this is not meant to imply the Freudian/Psychodynamic unconscious. The Freudian unconscious level refers to wishes, desires, and fears which are repressed from the conscious mind in order to reduce anxiety, though the existence of this level of consciousness is disputed and not common in psychological research today.

Finally, the nonconscious level would include things that we are almost never aware of. This would include many processes of the autonomic nervous system such as muscle contractions for heart-rate or digestion, or levels of activation in different brain areas. We simply don't have conscious access to these processes in our body even if we try to think about them.

Even if we can't quite address all the philosophical questions that consciousness raises we can still consider what our subjective experience of consciousness is like and try to understand it. So let's consider some of the traits that consciousness seems to have (though there is still disagreement on some of these) as well as some evidence supporting the existence of these traits.

Unity – Consciousness is generally singular. While our precise state of consciousness may change, it tends to be considered a single state, rather than multiple consciousnesses at once. In this way, our consciousness tends toward unity. Consider watching a movie and you'll realize that we automatically incorporate the sights, sounds, and emotions into a single consciousness, rather than experiencing them as separate entities.

Intentionality – Intentionality means that consciousness is always focused on something. Consciousness seems to always be directed toward particular objects, thoughts, or events. Even when we daydream and our minds are wandering, in each moment our consciousness seems to be focused on something, whether that something is an internal thought, a particular sensation, or an external stimulus.

Selectivity – Our consciousness seems to be selective. It is able to pick up some messages and perceptions while ignoring others. This can be seen in what's known as the Cocktail Party Phenomenon. Imagine that you are at a cocktail party, in a large room with a few dozen other people. People gather in clusters and there is the constant din of other conversations around you. In this situation, you are able to focus your attention on the particular conversation you are in, and everything else fades into a kind of background static.

It's not simply the case that you can't hear the others; it's that your attention is not directed toward them. In fact, if you were to eavesdrop on the conversation next to you, you might be able to hear it just fine. Now, without anything in the environment changing, your attention has selectively been placed on this other conversation, and the one you were previously in becomes background noise. We don't always have complete control of this selection process, however, as you've experienced if you've ever been in a conversation but then became distracted by hearing your name on the other side of the room. This cue can grab your attention and pull it to the other conversation. Hopefully you'll manage to switch your attention back to your present conversation before your partner asks a question, only to discover that you haven't really been listening.

This selective nature of attention can be tested in the laboratory in what's known as a dichotic listening task. In this design, participants attempt to listen to two messages simultaneously, one in each ear. Participants are asked to shadow one message by verbally repeating it. This ensures that their attention is focused on that message. When asked questions about the other message, however, participants show very little knowledge of it. In fact, they may not even notice if the voice of the other message changed or if the message was actually an incoherent jumble of words.

This type of research points out that we are not particularly good multi-taskers. Our attention doesn't divide well. So while you might occasionally manage to eavesdrop without getting caught, if you think you can text and drive you are wrong. You can drive, then text, then switch your attention back to driving, but you can't actually direct your attention to both activities at once. So while you may think you are skilled enough to multi-task (remember illusory superiority) the truth is that attention doesn't work that way. If you text and drive you put the safety of yourself and others at risk.

Our tiny spotlight of attention is actually much smaller than we think and anything going on outside of it is barely detected, if it is detected at all. This can be clearly seen in demonstrations of change blindnesschange blindnessFailure to detect changes in a scene when attention is not focused on the changing element.. In these studies, large changes can be made in the environment without people noticing, provided that their attention is directed elsewhere. In one clever study by Daniel Simons and Daniel Levin, a pedestrian asking for directions from a stranger was switched to a completely different person and in half of the trials the stranger didn't seem to notice the change.

A related phenomenon is inattentional blindnessinattentional blindnessFailing to notice an unexpected stimulus that appears in plain sight when attention is focused elsewhere., where we fail to detect an otherwise-obvious stimulus because our attention is directed elsewhere. This has also been demonstrated in studies by Simons and Christopher Chabris including a particularly well-known example involving basketball players. I don't want to give it away here (though perhaps I've said too much already) so I encourage you to check YouTube now for “the awareness test” and see just how well you can track the basketball players passing the ball.

**SPOILER ALERT**

Don't keep reading if you want to check your awareness in the Simons and Chabris demonstration. If you're already seen it or just watched it now, you may have missed (like more than half of the participants) the gorilla walking into the scene, beating his chest, then walking off. While your spotlight of attention was focused on the ball-passing by the white-shirted players, your mind filtered out the black-shirted players and as a result, inadvertently filtered out the gorilla costume as well. **END SPOILER**

Transience – Finally, our minds love to wander. William James compared consciousness to a stream, because it was always moving and flowing. Our minds are constantly flitting about, moving from sights to sounds and feelings to thoughts, sampling widely from the surfeit of possible stimulation.

To remember these 4 traits of consciousness – unity, intentionality, selectivity, and transience, imagine that you are moving through a cave in the dark with a single flashlight. Now imagine that the spot of light from this flashlight represents your consciousness. There is only one spot of light (unity) it is always shining on something (intentionality), you have some control over where you point it (selectivity) and you'll have a tendency to keep moving it as you explore the cave (transience).

We may wonder just how much we control our own consciousness. For a brief demonstration of the problem of mental control, I can simply challenge you not to think of a white bear for the next 5 minutes. In a study by Daniel Wegner, participants given this thought-suppression challenge thought of white bears far more frequently than participants who were not told to suppress thoughts of white bears. This as an example of an ironic process of mental control, in which our attempt to control our thoughts creates a counterintentional effect.

In addition to failures of conscious control, we may not realize that we've already ceded a great deal of control to unconscious processes. Even though our conscious attention tends toward unity, we also have subconscious processing that is occurring in parallel. This idea of simultaneous conscious and unconscious processing is known as Dual-Process Theory and it is often said we have a two-track mind: one track following our conscious experience, while the other track discreetly collects and processes information beneath our awareness. These tracks are also sometimes referred to as System 1 (unconscious) and System 2 (conscious). One way of getting a glimpse at the unconscious processing of System 1 is a technique known as priming.

Priming refers to how subtle cues in our environment can activate certain mental concepts which are then capable of influencing behavior. For a simple example, I could prime you by talking about sports, then ask you to quickly fill in the blanks below to create a word:

__ __ L L

You might come up with “ball”, but if I had previously mentioned shopping you might be more likely to fill in the blanks to create “mall”.

One of the most famous studies of priming, conducted by John Bargh and colleagues in 1996, involved priming participants for the concept of “elderly” by having them create sentences from scrambled words. For the experimental group, some sentences included terms like “Florida”, “wrinkle”, and “bingo”, while controls completed the same task with non-age related terms. Bargh and colleagues then secretly recorded the time it took participants to walk to the elevator after the task and found that the elderly-primed participants walked more slowly than the controls. This suggests that subtle cues in our environment can have measurable impact on our behavior, though this influence may be outside of our conscious awareness.

Another unconscious influence on our behavior is the mere-exposure effect, which is that we have a tendency to like things more when they are more familiar to us. While this relationship between familiarity and fondness isn't exactly shocking, it may surprise you that this relationship holds even when people aren't aware of being exposed to the stimulus. Research by Robert Zajonc (pronounced like “science” but starting with a “z”) and colleagues found that Chinese characters repeatedly flashed on a screen too quickly for conscious awareness were later rated as more likeable than other characters by participants who couldn't read Chinese. Similar effects of repeated exposure have been found for nonsense words, tones, and even people's faces.

Advertisers are acutely aware of the effect of familiarity, and as a result they spend millions of dollars getting products in front of our faces. Most people insist that ads don't affect their behavior, but this is probably because some of the effects are occurring unconsciously. It's not that you see an advertisement and immediately run to the store, but rather that you may unconsciously develop greater fondness for that particular brand because you have seen it before.

Of course, the effects of priming and mere-exposure are subtle and it seems that environments must be carefully controlled in order to observe them. They certainly shouldn't be seen as magical brain-washing or powerful subliminal mind-control techniques. Nevertheless, they should make us question just how much we control our conscious behavior and how much influence is exerted outside of our conscious awareness.

You may think, as many people do, that sleeping is a type of unconsciousness, but this isn't accurate. Despite expressions like “dead to the world”, sleepers do have some awareness of their surroundings. They manage to keep their bodies in their beds, and in the case of dreaming, they certainly have a vivid experience of being asleep. In fact, stimuli from a sleeper's environment may even be seamlessly incorporated into dreams, which you may have experienced if the sound of your alarm clock has ever found its way into your dreams as a blaring fire alarm, a ringing phone, or a singing banana.

So rather than unconsciousness, we should think of sleeping as another state of consciousness that differs from waking life. Instead of sleep and wakefulness as an on/off switch for consciousness, we should think of a dimmer switch, which allows us to slide back and forth between different levels of awareness.

Our sleeping pattern follows a circadian rhythmcircadian rhythmThe approximately 24-hour biological cycle regulating sleep, wakefulness, and many physiological processes., which is really just a way of saying a daily pattern of wakefulness and sleepiness (circadian derived from Latin: circa - “about” and diem - “day”). Our circadian rhythm is influenced by environmental factors, known as zeitgebers (German for “time-givers”) which help to set this internal clock.

One of the most most powerful zeitgebers is light. When light hits your retina, messages are not only sent to the occipital lobe for visual processing, they are also sent to the suprachiasmatic nucleussuprachiasmatic nucleusThe brain's master clock in the hypothalamus that synchronizes circadian rhythms with the light-dark cycle., an area of the hypothalamus. In the presence of light (especially wavelengths corresponding to blue light), the suprachiasmatic nucleus inhibits the pineal gland from releasing melatoninmelatoninA hormone released by the pineal gland in darkness that promotes sleep and regulates the circadian rhythm. into the bloodstream. Melatonin is a hormone which, when released into the bloodstream, causes us to feel drowsy. Through this process of inhibiting melatonin release, light helps to keep us feeling alert, while darkness helps bring drowsiness.

This process probably worked quite well in setting our circadian rhythm for millions of years of our evolutionary history, but the ubiquity of artificial light in most of our lives today may be interrupting this system. While our ancestors only really had bright light from the sun, we can have bright light any time we want. The darkness of dusk that told our ancestors to unwind and stay in the safety of shelter now simply signals us to turn on the lights.

If you have trouble falling asleep at night, light may be part of the problem and limiting your exposure to it in the evening may help you to fall asleep more easily. You may even consider using blue-light blocking glasses in the evening or downloading programs like f.lux which reduce the amount of blue-light emitted by your laptop or phone screen after sunset.

Light is not the only zeitgeber that influences our level of alertness. The timing of our meals, the ambient temperature, and our social interactions also play a role in the circadian rhythm. This may explain how you managed to stay awake all night at slumber parties and why it's so easy to fall asleep in a warm room while a lecturer drones on and on without any chance of interaction.

The settings of this internal clock also vary with age, as teenagers tend to be “night-owls” whose concentration and attention peak later in the day or evening, while older adults tend to be “larks” who perform best in early morning, then decline as the hours go by. This is clearly seen in the classic class-time conundrum, as adults (parents and teachers) set the times that work best for them, while teenagers are alert at 11pm but stumbling and slumbering through early morning classes.

As we sleep through any given night, we move through a number of different stages of sleep. These different stages can be identified by their differing patterns of brain activity, as recorded by an EEG (electroencephalogram). These measurements of electrical activity in the brain are recorded in the form of waves, with peak and valleys, and the resulting patterns are where we get the term “brain waves”. In an awake but relaxed, drowsy, or meditative state, the brain produces “alpha waves”, while a state of vigilance produces “beta waves”.

When we first fall asleep, we move through the following stages of sleep. The first 3 stages are referred to as NREM, for Non-Rapid-Eye-Movement sleep.

NREM Stage 1 – Stage 1 is characterized by de-synchronized theta waves; slow irregular waves of activity. In this stage, sleepers may experience brief dream-like visions, known as hypnagogic imagery, and occasionally experience sudden twitches and falling sensations, known as hypnic jerks. This stage may last for only a few minutes before moving to stage 2.

NREM Stage 2 – Theta waves continue, though occasionally interrupted by sudden bursts of activity, known as sleep spindlessleep spindlesBursts of high-frequency brain activity characteristic of Stage 2 NREM sleep.. In this stage we also see high amplitude spikes known as K-complexes, which are hypothesized to reduce cortical arousal and help maintain sleep. When you first fall asleep, this stage will generally last for around 15-20 minutes. Throughout the course of a night, about 50% of sleep time will be spent in Stage 2 sleep.

NREM Stage 3 – By stage 3 we see more obvious changes in brain activity as the waves increase their amplitude and decrease their frequency while also becoming more synchronized, resulting in “delta waves”. This stage is considered to be the stage of deepest sleep and lowest awareness of surroundings. If you’re groggy and confused when someone wakes you (known as sleep inertia), there’s a good chance that you were in this “slow-wave” sleep at the time. Note: you may see reference to Stage 4 sleep in some texts; the American Academy of Sleep Medicine reclassified the stages in 2007, combining stage 3 and 4 into a single stage.

So far this probably seems as you’d expect; the longer you’ve been asleep, the deeper the level of sleep. But after about an hour, something bizarre happens. The depth of your sleep lessens as you rise back up to stage 2, and then you enter the most interesting stage of all.

REM sleepREM sleepRapid eye movement sleep — the stage characterized by vivid dreaming, muscle paralysis, and brain activity resembling waking. or rapid-eye-movement sleep, is sometimes referred to as paradoxical sleep, and with good reason. In contrast to the other stages, in REM heart rate, blood pressure, and respiration increase, along with physical signs of sexual arousal. Every 30 seconds or so your eyes begin moving around under your eyelids (hence the name). Your brain activity closely resembles that of a waking state, and yet your body becomes paralyzed. People who are awakened from Non-REM stages may report some dreamlike imagery, but those awakened from REM report vivid dreaming.

Although the processes of sleep are not yet fully understood, REM seems to be particularly important for the consolidation of memory. The importance of REM can be seen in the fact that people (and animals) who are temporarily deprived of REM sleep for a night will experience a rebound effect; spending more time in REM than usual during subsequent sleep. Babies spend more time in REM than adults, and people who are experiencing higher levels of stress will also spend more time in REM when they sleep.

For most people, an entire sleep cycle from Stage 1 to a completed period of REM will last about 90 minutes. At this point the cycle is repeated, though in subsequent cycles we spend less time in deep sleep (by the end of the night skipping slow-wave sleepslow-wave sleepStage 3 NREM deep sleep — associated with physical restoration, immune function, and growth hormone release. completely) and spend more time in REM sleep. While initial REM stages may last for 15 or 20 minutes, later cycles may have REM sessions lasting 45 minutes to an hour.

One way of assessing the importance of sleep is to consider what happens when we don't get it. This can be considered either by examining the effects of chronic sleep deprivation, in which people are repeatedly not getting enough sleep, or by acute sleep deprivation, in which people stay awake continuously.

Physical effects of Sleep Deprivation

Sleep deprivation causes a number of physical changes in the body. Physical symptoms of sleep deprivation include fatigue, dark circles and/or bags under the eyes (caused by the very thin layers of skin in this area becoming more pale and allowing blood vessels to become more visible), fluctuations in hormone levels, and reduced performance on physical tasks.

Chronic sleep deprivation is associated with obesity, which may be a result of several hormonal changes which occur during sleep deprivation. Going without enough sleep increases levels of the hormone ghrelin, which increases feelings of hunger, and deprivation decreases the hormone leptin, which helps to signal satiety. As a result, sleep-deprived people are more likely to have cravings for food and also likely to eat more before feeling full. Sleep deprivation also reduces willpower, which means that when those cravings hit they may be even harder to resist.

Sleep deprivation also increases levels of the stress hormone cortisol, which can trigger the body to store fat. This stress response also means that sleep deprivation suppresses the activity of the immune system. This means that people who don't get enough sleep are more likely to get sick, and also explains why when we do get sick we tend to spend more time asleep (in order to activate the immune system).

Cognitive Effects of Sleep Deprivation

Sleep deprivation has profound effects on cognition and attention. Both chronic and acute sleep deprivation impair concentration, memory, judgment, coordination, and reaction time. These cognitive deficits shouldn't just concern you when it comes to your exam performance after an all-nighter. The potential for serious injury and death from sleep deprivation is high. Studies of “drowsy driving” have found impairments similar to drunk driving and driver fatigue has been estimated to be responsible for 100,000 crashes, 1,550 deaths and 71,000 injuries every year in the United States alone. So even if you join Edgar Allan Poe in loathing sleep as “little slices of death”, remember that trying to do without sleep may lead to a death far more permanent.

The most common sleep disorder is insomniainsomniaPersistent difficulty falling asleep, staying asleep, or achieving restorative sleep., and it is estimated that about 10% of adults will suffer from insomnia at some point in their lifetime. Insomnia is a persistent difficulty or inability to enter the sleep state, or to remain asleep, often despite feeling tired. So while we all occasionally have difficulty getting to sleep at night, in most cases this wouldn't be considered to be clinical insomnia.

While you may think that sleeping pills (or an alcoholic “night-cap”) would help those with insomnia, these aren't recommended. While sleeping pills may aid muscle relaxation or reduce anxiety to help patients enter the sleep state, unfortunately they reduce the quality of REM sleep. This means that while patients may spend more time sleeping, they end up getting less REM sleep and as a result still feel tired.

Insomnia sufferers also have a tendency to underestimate how much sleep they are getting, often believing they are sleeping half as much as they actually are. This may occur because they enter the sleep state and reawaken without realizing they were asleep. If they repeatedly check the clock throughout the night they may think that they were awake until 2 or 3am, when some of that time was spent asleep. They may also recall waking during the night and believe that they stayed awake much longer than they actually did.

Another common sleep disorder affecting about 5% of people (though more common in males) is sleep apneasleep apneaA sleep disorder in which breathing repeatedly stops during sleep, causing fragmented sleep and oxygen deprivation.. In this disorder, when muscles in the throat relax during sleep, the tongue and epiglottis obstruct the flow of air. This is also what causes those strange sounds of snoring, except in sleep apnea airflow is completely blocked. This blockage of airflow causes the patient to awaken in order to breathe. Patients with sleep apnea may not remember awakening throughout the night, but report feeling tired and lethargic despite what appears to be adequate sleeping time.

Obesity increases the risk of sleep apnea, though as we've seen already, sleep deprivation (which would be a side effect of sleep apnea) also increases the risk of obesity, so this interaction could be working both ways. A common treatment for sleep apnea is to use a CPAP (continuous positive airway pressure) machine. This device consists of a mask, worn at night, which slightly increases air pressure on the throat, helping to keep the airway open and allowing the patient to remain breathing (and sleeping).

Sleep walking (or somnambulism) occurs during the deep stages of slow-wave sleep. The sleeper may get out of bed, wander around, and even eat or perform other behaviors while still in the sleep state. Sleep walking is more common in young children, especially males, and often goes away on its own by adolescence. Episodes of sleepwalking and behaviors performed are rarely recalled the next morning.

Children are also more likely than adults to suffer from night terrorsnight terrorsEpisodes of intense fear and arousal occurring during slow-wave sleep, usually without remembered dreams.. In night terrors, the person wakes up in the middle of the night and may scream, feeling an overwhelming sense of fear, and usually doesn't remember the experience in the morning. Like sleepwalking, night terrors also tend to fade by the end of childhood.

REM Sleep Behavior disorder is a rare disorder in which the usual paralysis and loss of muscle tone (muscle atonia) of REM sleep does not occur. This means that sufferers are able to engage in “dream enactment”, which can have dangerous consequences. They may kick, punch, scream, or jump out of bed, potentially injuring themselves or their bed partner. REM sleep behavior disorder can be treated with muscle relaxants to reduce activity, in addition to creating a safer environment for the sleeper which may even include a special sleeping bag that helps to restrict movements.

NarcolepsyNarcolepsyA sleep disorder involving sudden, uncontrollable attacks of sleep and cataplexy — linked to deficiency in hypocretin. is a rare sleep disorder affecting about 1 in 2000 people (0.05%), in which patients suffer from an irrepressible need to sleep, even though they are spending adequate amounts of time sleeping at night. They repeatedly lapse into sleep and often also experience cataplexy, a sudden loss of muscle tone. The sudden attacks of sleep generally only last for a few minutes and may occur at any time, making it difficult for sufferers of narcolepsy to live a normal life. Narcolepsy sufferers tend to enter the REM state very quickly after falling asleep, meaning that they spend less time in slow-wave stages of sleep, which may relate to their feelings of drowsiness during the day.

Narcolepsy can be treated with stimulantsstimulantsDrugs that increase neural activity and arouse bodily functions — includes caffeine, nicotine, cocaine, and amphetamines. (such as Modafinil) which promote wakefulness, though these do not cure the disorder. Some sufferers remain awake and aware of their surroundings during cataplexy but are unable to move. People nearby may attempt to “awaken” the person with pinches or shouting. The sufferer can feel and hear these attempts but is unable to respond.

You may have heard of polyphasic sleeping schedules, which involve splitting sleep time up into several separate chunks throughout a 24 hour period. Attempts to adopt these schedules seem to be spurred by claims from Thomas Edison that sleep is a “complete waste of time” and they are encouraged by life-hackers seeking to supposedly maximize sleep efficiency. These schedules are often claimed to derive from the odd sleeping habits of eminent thinkers like Leonardo DaVinci and Nikola Tesla, though evidence that these figures actually followed these types of schedules for extended periods is scant to nonexistent.

We should note that much of the initial research on polyphasic schedules conducted by Claudio Stampi was intended to determine sleep efficiency in a particular subset of people: solo-sailors during lengthy competitions in which full periods of sleep were not possible. Stampi tested a number of possible ways of dividing sleep in order to assess which allowed for greater physical performance over a relatively short period of time. Life-hackers tend to ignore that these schedules weren't intended to be adopted as routine sleeping habits, but were for specific short-term situations which necessitated some level of chronic sleep deprivation.

We should also avoid thinking that just because there are names for these schedules this means they are actually viable ways of organizing quality sleep. Unfortunately creating names like the “Everyman” and “Uberman” schedule may give a false sense of credibility to these schedules. This is related to a cognitive error known as the nominal fallacy, which is the flaw of thinking that because we have a name for something we actually understand it. So if I were to invent the “Deca-doze Distribution” of sleeping for 10 minutes every 2 hours the mere fact that I've given it a scientific-sounding name might make people more likely to believe it's something that can be done.

You should also note that in evolutionary terms these schedules don't make much sense. We have evolved to be alert and awake during the day (when we can hunt and gather) and sleep during the night (when it's dark and we are more vulnerable). This rhythm indicates that we are best suited to a single long session of sleep (monophasic) or perhaps a biphasic schedule, which is a large chunk of sleep at night, with the addition of an early afternoon siesta. Attempting to drastically deviate from the circadian rhythm which has developed over millions of years seems unlikely to create benefits, and as we've already seen, the risks of sleep deprivation are great.

So if you've been tempted to try adopting one of these polyphasic schedules, remember that sleeping less in exchange for more grogginess, irritability, cognitive deficits, and a higher risk of fatality from accidents doesn't seem like a particularly wise trade-off. There's a certain irony to the belief that if you want to be successful and productive you need to learn how to sleep less. In actuality, achieving high levels of performance, in both cognitive and physical tasks, seems to necessitate spending more time in sleep. Sleep helps to consolidate new memories, enhance concentration, and improve reaction time, endurance, mood, and energy levels. So ignore those admonitions from Edison and help uncover your potential by spending more time under the covers.

Freud’s approach to understanding dreaming was based on the assumption that dreams were representations of unconscious desires. Because these desires are too anxiety-producing for us to consciously consider, they are not directly revealed. One way they emerge, according to Freud, is when we are dreaming.

He believed that dreams consisted of two features, the manifest contentmanifest contentIn Freud's theory, the remembered story of a dream. and the latent contentlatent contentIn Freud's theory, the underlying unconscious meaning or wish disguised in the manifest dream content.. The manifest content is what we are shown, meaning what we actually dream about. So if we dream about riding a train, arguing with a talking dolphin, or watching a burning tree, these would be the manifest content.

The latent content, however, is the hidden message behind the dream. It’s those anxiety-producing unconscious fears and desires that our conscious mind needs to be shielded from. So our dream about a train may be about sex, the dolphin might represent conflict with our mother, or the burning tree the death of a friend. Freud believed that a therapist could analyze the manifest content of a patient’s dreams and, over time, uncover clues about the unconscious forces shaping the patient’s personality.

There are two main problems with this approach to understanding dreams. The first is that we frequently dream explicitly about our desires and fears. These often manifest themselves quite directly in dreams and we have conscious access to these themes. We actually do dream of having sex, fighting with a parent, losing a friend, or any number of other stressful and anxiety-producing events. If these desires must be hidden from consciousness, why would they sometimes appear in the manifest content?

Secondly, there are infinite possible interpretations of the manifest content, so we can never be sure which interpretation is correct. What your therapist thinks a train or a dolphin means may actually reveal more about the therapist’s mind than it reveals about your own.

So while Freud’s notion that there are hidden clues to the unconscious in dreams gained some popularity, it ultimately failed to provide a satisfying answer to why exactly we dream what we dream. It may be true that dreams reveal some aspects of our thoughts as well as our hopes, fears, and desires. What doesn’t seem to be true is that these elements are revealed through predictable patterns and symbols.

In 1977, J. Allan Hobson and Robert McCarley proposed a new theory of dreaming, the activation-synthesis model. The activation-synthesis model suggests that during sleep, brain activation occurs somewhat randomly, and these patterns of random activation are combined and interpreted (synthesis) by the brain. This results in the bizarre (and characteristic) features of dreams. In this model, dreams are seen as the brain’s flailing attempt to make sense of these unusual patterns of activation.

This approach attempts to explain the apparently inexplicable nature of dreams by suggesting that often our brains are dealing with patterns of activation that simply don’t occur in waking life. The brain is being forced to come up with explanations for bizarre patterns of activity and we’re just left watching the show (and scratching our heads as to what the director was thinking). If, for instance, you find yourself dreaming that you are now vacationing with your 3rd grade art teacher, it’s probably not because of some repressed sexual desire (as a Freudian might suggest), but rather that your memory for that teacher just happened to be stimulated at the same time as your memory for last year’s travels. In a valiant attempt to reconcile this new pattern, your ever-explaining brain creates a storyline in which the two coexist.

Since the activation-synthesis model was first proposed, there has been considerably more research on the patterns of activation that occur during REM sleep, suggesting that perhaps the activation isn't quite random. This information-processing dream theory considers that the activation patterns that occur during REM serve other purposes and are not simply random noise. Neural activation in dreaming may allow our brains to sift through new experiences, revisit old memories, and maintain neural connections and networks.

One way that this can be seen is in how our dreams often incorporate “day residue” of our present situations and experiences, combined with memories from years or even decades before. If we spend hours playing a video game during the day, imagery from the game tends to show up in dreams that night but may be combined with other memories or situations. If, as Robert Stickgold has suggested, one role of sleep is to consolidate memories and integrate our experiences into a cohesive sense of self, it may no longer come as a surprise that dreams combine our recent experiences and learning with other memories. Rather than random activation, this may reflect sleep's role in reorganizing information and considering alternatives in order to inform our future responses.

This might also account for common themes in dreams, as we all share many similar problems, fears (predators or exams), sources of embarrassment (oops I forgot my pants), or worries for the future (I’ve lost my teeth and hair) that our minds are simulating and working out responses to. At the same time, it accounts for individual differences, as how our brains choose to interpret, explain, and react to these simulations may reflect something of our own unique experiences and viewpoints.

Finally, a section on dreaming wouldn't be complete without mentioning lucid dreaming. Lucid dreaming is when a dreamer becomes aware of the dream state, but remains asleep. The dreamer may then be able to take conscious control of the dream and direct the course of events. This raises some questions about the nature of consciousness during dreaming and how awareness that one is dreaming may be separated from the dream experience itself. Stephen LaBerge has spent decades studying lucid dreaming and believes that anyone can learn to lucid dream on a regular basis. He has written several books on learning to lucid dream and believes that lucid dreaming can help to foster greater creativity, insight, and new perspectives and interpretations of events and behaviors.

In chapter 3 we looked at several drug and neurotransmitter interactions such as nicotine and acetylcholine, and alcohol and GABA, to understand how chemical interactions in the brain influence behavior. What we didn't address, however, is how these might influence our consciousness. In this section, we'll look at how psychoactive drugs, substances which alter the chemistry of the brain, are capable of altering our state of consciousness.

Generally speaking, the brain doesn't want to be messed with, so to keep things under control, the blood-brain barrier prevents most things in the bloodstream from getting into the brain. This blood-brain barrier works by only allowing certain molecules, like vital nutrients, through its special channels. This is generally a good thing, and why brain viruses and infections are so rare. Even if an infection is in your body and traveling in your bloodstream, the tight-knit endothelial cells of the blood-brain barrier can usually provide an adequate security network. The downside is that when you do have an infection in your brain, it's especially difficult to get medication in to fight it.

Some chemicals, however, are able to sneak through this barrier, gain access to the brain, and influence its functioning. Once inside the brain, these chemicals can travel to synapses and affect neural communication. Some chemicals boost the message of a neurotransmitter, either by mimicking the action of the neurotransmitter, blocking its removal from the synapse, or stimulating its release. These drugs are considered to be agonists for the neurotransmitter they influence. Other drugs, however, do the opposite and decrease the effects of a neurotransmitter by blocking its receptor sites, increasing its removal, or decreasing its release. These drugs are antagonists for the neurotransmitter affected.

This agonist/antagonist categorization doesn't address the effects the drugs have on behavior or cognition. Based on their effects, drugs can be roughly categorized into 3 main groups: depressantsdepressantsDrugs that slow central nervous system activity — includes alcohol, barbiturates, and benzodiazepines., stimulants, or hallucinogenshallucinogensDrugs that distort perception and evoke sensory experiences without actual sensory stimulation.. Of course, because it's possible to influence more than one neurotransmitter or more than one brain area or body function, some drugs may fit into more than one category.

In considering the effects of these different types of drugs, we should remember that the body is constantly trying to maintain a state of homeostasis, the balance needed to maintain normal functioning. Repeated introduction of drugs into the brain causes changes, known as neuroadaptation. This is how tolerancetoleranceThe need for increasing doses of a drug to achieve the original effect, resulting from the brain's adaptation. to a drug builds over time. After repeated exposure, the brain builds a resistance to the effects of the drug, so a greater dosage is required to achieve the same effects, perhaps explaining why just one cup of coffee doesn't get you going like it used to.

After a tolerance has developed, neuroadaptation also explains why going without the drug can be difficult. This is known as withdrawalwithdrawalUnpleasant physical and psychological symptoms that occur when a person stops using a drug they are dependent on.. Essentially the brain has adapted to having the drug around, and has developed a dependence on the drug's effects. In the case of caffeine, sudden cessation may result in a minor headache, but for more powerful drugs, withdrawal can be an overwhelmingly painful experience. Intense cravings combined with physical pain can drive a user back to the drug, even though he may rationally know that it is destroying his life.

This physical addiction to the chemical reactions a drug causes is not the only type of addiction, and users may also experience psychological addiction to a substance. In this case, people believe they need the drug, or find using it to be a way of coping. Alcohol is a good example of a drug that is physically addictive but also has strong psychological components of addiction. People may feel a desire for alcohol in order to function in particular social situations or in order to deal with disappointment, stress, or anxiety. Even after the physical symptoms of withdrawal have faded, a former alcoholic may still have difficulty dealing with the psychological components of addiction in certain situations.

Stimulants are drugs which speed up processes in the body and stimulate the autonomic nervous system. These drugs increase heart rate, blood pressure, and breathing, and may increase our state of vigilance while decreasing feelings of tiredness. In addition to this stimulation, some stimulants activate the reward area of the hypothalamus, triggering a rush of dopamine that causes short-lived feelings of euphoria and well-being. Common stimulant drugs include caffeine (which is the world's most commonly used psychoactive drugpsychoactive drugA chemical substance that alters mood, perception, or behavior by affecting neurotransmitter activity in the brain.), cocaine, amphetamines, methamphetamine, and ecstasy (MDMA – methylenedioxymethamphetamine).

Depressants have the opposite effect on the nervous system, slowing processes and inhibiting activation. This causes slowed heart rate and breathing, and reduced muscle tension. Depressants include alcohol (specifically ethanol) and tranquilizers (also known as anxiolytics or anti-anxiety drugs) which include barbiturates and benzodiazepines (like Valium and Xanax).

Overdose of depressant drugs can lead to enough inhibition of function to induce a coma or even cause death. Withdrawal can also be dangerous, as the body's dependence on the inhibiting effects of regular use mean that sudden cessation can cause excitotoxicity. Dependency causes the nervous system to be overstimulated when the depressant drug is no longer suppressing function, causing anxiety, seizures, and in extreme cases, death.

Narcotics (including OpiatesOpiatesDrugs derived from the opium poppy — or synthetic equivalents — that reduce pain and produce euphoria by binding to opioid receptors.) are sometimes classified as a separate category of drugs but can be considered depressants because of their inhibiting effects on the nervous system. The word narcotics comes from the Greek root narko meaning “numbness” or “stupor”. The term narcotics can be misleading though, as legal definitions differ from medical definitions. In the United States any prohibited drug may be referred to as a narcotic, so the term can refer to cocaine (a stimulant) and marijuana (a hallucinogen) even though in medical terms neither would be considered a narcotic.

In medical terms, narcotics are pain-relievers that mimic the body's own natural painkillers (endorphins) and include morphine, heroin, methadone, oxycodone, codeine, and opium (from which opiates and opioids get their name). These drugs block pain messages and provide a sense of euphoric, drowsy bliss for the user. Unfortunately, neuroadaptation occurs rapidly with opiates, causing the body to reduce endorphin production, thus leaving it unable to manage pain well on its own. Without natural endorphins to block their pain, recovering addicts face an agonizing withdrawal process where it can seem the only thing to stop their pain is the very drug they are trying to avoid. This torturous withdrawal process explains why these drugs can exert such a powerful influence over users.

The last category of psychoactive drugs includes those drugs which alter perception of reality and identity, and have the potential to induce sensory hallucinations. Hallucinogens (also known as psychedelics) include LSD (lysergic acid diethylamide), mescaline, psilocybin mushrooms, marijuana, PCP (phencyclidine), ketamine, and ecstasy (which is also a stimulant).

The effects of hallucinogenic drugs are considered to be less predictable than other drugs and seem to be more dependent on psychological factors such as the user's expectations and emotional state. Another difference from stimulants and depressants is that hallucinogens may remain in the body considerably longer. For instance, by-products of THC (delta-9-tetrahydrocannabinol) in marijuana may remain in the body as long as a month, and this lingering means that subsequent uses may actually have a stronger effect than the initial use. This may allow regular users to get high using a smaller dose of the drug and is referred to as reverse tolerance.

With a few exceptions (like PCP and ketamine) the physical withdrawal and dependency seen in other drug types is not common with hallucinogenic drugs. While animals will press levers thousands of times to get another hit of coke or meth, they generally won't work to get hits of LSD or psilocybin. As a result, these drugs generally aren't considered to be physically addictive in the same way as heroin, cocaine, alcohol, or even caffeine.

This does not mean that addiction isn't possible, however, as psychological addiction may still occur, particularly if these drugs are used to escape negative emotions or stress. The fact that they don't tend to cause withdrawal also doesn't mean that they aren't harmful. There are still a number of negative effects associated with their use including anxiety, paranoia, and problems in learning and memory formation.

While all the drugs mentioned above have physiological effects on the body, expectancy and beliefs also influence how they affect consciousness. While this is especially true of hallucinogens, it's also true of other drug types. People can be duped into believing that decaf coffee has improved their alertness (if they don't know it was decaf) or that non-alcoholic beverages have made them tipsy. These effects of beliefs and expectations mean that drugs aren't the only ways of changing our state of consciousness and it has been suggested that hypnosishypnosisA state of heightened focus, relaxation, and suggestibility induced by a hypnotist's suggestions. and meditationmeditationA practice of focused attention or open awareness used to quiet the mind and reduce stress. can also create altered states of consciousness.

In considering what hypnosis is, perhaps we should start by considering what hypnosis is not. Despite what you may have seen in a stage show, on television, or in movies, hypnosis is not a magical state of mind-control in which a hypnotized subject obeys the every whim of the hypnotist. Instead, we can think of a hypnotic state as a state of relaxation, focused attention, and increased imagination. This state is generally entered via hypnotic induction, in which the hypnotist encourages the subject to become relaxed, then gradually makes suggestions to the subject (your eyelids are becoming heavier, your eyes are closing, etc.). People vary in how strongly they respond to these suggestions, and this is referred to as their hypnotic suggestibility. Some people are considered to be “highly hypnotizable” and become absorbed in the suggestions of the hypnotist.

We shouldn't equate hypnotic suggestibility with mere gullibility, however, and when subjects are given this negative connotation their hypnotic suggestibility sharply decreases. We might think of hypnotic suggestibility as an ability to focus attention and imagination on the suggestions of the hypnotist. A sense of will remains, however, and subjects who have been hypnotized will not perform tasks that they would not otherwise do.

The increased state of imagination and attention does allow some therapeutic use for hypnosis, the most prominent of which is pain reduction (analgesia). Subjects who are hypnotized may also have greater access to their own healing powers, which may be similar to the placebo effect. Hypnosis has been used to successfully treat stress-related skin problems, asthma, and obesity. Its use in treating addictions to alcohol, nicotine, and other drugs, however, has not been shown to be as successful.

Despite the popular perception, hypnosis is not able to increase accuracy of past memories. As we saw in Chapter 6, our memory is subject to failures and biases, and unfortunately hypnosis is unable to overcome these. One thing it is able to do, however, is make subjects more confident in the accuracy of their memories, even though the memories are not actually more accurate. This can be a dangerous combination, particularly when these supposed recovered memories involve allegations of crime or abuse.

While it can't successfully recover repressed memories, hypnosis does seem to be able to reduce memories of the hypnotic session itself, known as posthypnotic amnesia. Subjects can also engage in directed forgetting, in which they respond to suggestions that certain information or experiences will not be remembered following the session.

One theory for explaining the behavior of hypnotized subjects is that they are like actors on a stage. They are obeying the hypnotist, who acts as a director and manages their perceptions. This is known as Role Theory of Hypnosis, and if we accept this explanation, we might think that hypnosis is not in fact an altered state of consciousness.

Another theory, however, suggests that hypnosis really is a different state from normal wakefulness and involves a division of consciousness. This Dissociation Theory, proposed by Ernest Hilgard, notes that hypnotized subjects may continue to follow suggestions even when they believe they are not being observed. This would indicate that hypnosis is more than just playing along. The fact the hypnosis can also effectively be used to manage pain suggests that it may actually be altering the perceptual experiences of subjects. Hilgard demonstrated this by asking hypnotized subjects to hold their hands in icy water. These subjects were then asked about whether they were experiencing pain. While subjects said they weren't experiencing pain, they still showed awareness that the icy water was actually painful. This suggested to Hilgard that the subjects were splitting their consciousness between awareness of the pain (which they had) and the experience of the pain (which was reduced).

Another possible altered state of consciousness can be seen in meditation. In many ways, hypnosis and meditation are quite similar, as they both are a state of relaxed awareness, though meditation does not necessarily focus on particular suggestions. While there are many varieties and traditions of meditation, we will briefly focus on two types: focused awareness meditation and mindfulness meditation. Both of these practices involve cultivating a relaxed and calm state of mind.

In focused attention meditation the meditator chooses a single focus of attention and attempts to maintain this focus. The sole focus of attention may be one's breathing or it may be a mantra; a word or phrase that is repeated (mentally or chanted). While you may have heard of some of the familiar mantras like “Om” or “Hare Krishna” that are used by some groups, any word at all can be used. The importance of the mantra is to track one's awareness and notice when it has deviated.

Another type of meditation is mindfulness meditation. The main difference here is that rather than maintaining a single focus, the meditator attends to all the sights, sounds, feelings, and thoughts that occur, but without becoming attached to any of them. Jon Kabat-Zinn describes mindfulness as “paying attention in a particular way: on purpose, in the present moment, and nonjudgmentally”.

There may be similarities here to the dissociation theory of hypnosis, where subjects seem to separate their awareness of sensations from their experience of those sensations. Experienced meditators engaging in mindfulness meditation have shown similar types of analgesia, having awareness of pain but having reduced experience and emotional reactivity to the pain.

Herbert Benson has researched how the practice of meditation elicits the “relaxation response” a metabolic change that activates the parasympathetic nervous system. This is essentially the opposite of the “fight or flight response”. This relaxation response reduces activation of the sympathetic nervous system, decreasing heart rate, blood pressure, and stress hormones, while increasing relaxation, digestion, and immune function.

While this isn't intended to be a comprehensive guide to meditation, I thought I would give readers a few pointers if they are interested in how to begin. Meditation isn't all that complicated, and all that you really need to do is set aside some time to sit quietly and calm your mind.

The first point that beginners may struggle with is the widespread misconception that meditation is some sort of esoteric and mystical experience. You don't need to understand how to balance your qi, align your chakras, or look out your third eye in order to meditate properly. You don't need to travel to Tibetan mountaintops or gaze at Ganesh under the guidance of a guru in order to get the calming benefits that meditation can give. While understanding these cultural traditions and practices can be fascinating, it's not a prerequisite for getting started.

Another problem that plagues people who want to start meditating is the feeling that they just can't do it. Their mind wanders, they feel uncomfortable or restless, and they give up, thinking that meditation is not for them. If you're looking to start regular meditation, remember that trying to maintain a single focus, getting distracted, then bringing your mind back to focus is what meditation is. It doesn't mean that you're doing it wrong or that it's not for you. Focus, distraction, and refocus are supposed to happen, so accept this cycle. Continuing to sit quietly and face down distraction and discomfort is a challenge, and that's exactly the point.

Choose a comfortable sitting posture (lying down usually leads to falling asleep, which is not what we want), choose something to focus on (your breathing, a mantra, or your present sensations), and you've begun to meditate. If you can embrace the fact that you aren't waiting for anything miraculous to happen and you recognize that catching your mind wandering is what meditation is, then you're on the right path toward cultivating this practice. Realizing that this is a practice that needs to be cultivated means you don't need to start with 45 minutes or an hour all at once. Start with a small goal that is attainable (maybe just 5 minutes per day) then gradually build as you get more comfortable with the practice.

While this is all you really need to get started, if you want to read more about meditation, I highly recommend the writing of Jon Kabat-Zinn, especially “Wherever You Go, There You Are” which was quoted above. His writing is clear, accessible, and inspiring, and is what has helped me most with meditation. I hope that you'll consider creating the habit of regular meditation and I wish you the best on this journey!