Psychology2016

Consciousness 145

person? For most people, a missed night of sleep will result in concentration problems
and the inability to do simple tasks that normally would take no thought at all, such as
loading a DVD into a player. More complex tasks, such as math problems, suffer less
than these simple tasks because people know they must concentrate on a complex task
(Chee & Choo, 2004; Lim et al., 2007).
Even so, sleep deprivation, or loss of sleep, is a serious problem, which many
people have without realizing it. Students, for example, may stay up all night to study
for an important test the next day. In doing so, they will lose more information than
they gain, as a good night’s sleep is important for memory and the ability to think well
( Gillen-O’Neel et al., 2012). to Learning Objective PIA.5. Even a few nights of
poor sleep have serious consequences for mental and physical functioning (Jackson et al.,
2013; Van Dongen et al., 2003). Some typical symptoms of sleep deprivation include trem-
bling hands, inattention, staring off into space, droopy eyelids, and general discomfort
(Naitoh et al., 1989), as well as emotional symptoms such as irritability and even depres-
sion. to Learning Objective 14.9. Add to that list an increased risk of insulin
resistance, which can lead to diabetes (Matthews et al., 2012), and even possible delays in
the onset of puberty (Shaw et al., 2012). And if you are a Twitter user, beware—a study
found that users suffering from sleep deprivation tend to create more negative tweets,
a sign of increased risk for psychological issues (McIver et al., 2015). As you will see in
the feature titled “Weight Gain and Sleep” later on in this chapter, one common cause of
sleep deprivation is a disturbance of the sleep–wake cycle, something that is a common
problem among college students.

The Stages of Sleep

4.5 Identify the different stages of sleep.

So are there different kinds of sleep? Do you go from being

awake to being asleep and dreaming—is it instant?

There are actually two kinds of sleep: rapid eye movement sleep (R; REM) and
non-rapid eye movement sleep (N; NREM). REM sleep is a relatively psychologically
active type of sleep when most of a person’s dreaming takes place, whereas NREM sleep
spans from lighter stages to a much deeper, more restful kind of sleep. In REM sleep, the
voluntary muscles are inhibited, meaning that the person in REM sleep moves very little,
whereas in NREM sleep the person’s body is free to move around (including kicking
one’s bed partner!). There are also several different stages of sleep that people go through
each night in which REM sleep and NREM sleep occur. A machine called an electro-
encephalograph allows scientists to record the brain-wave activity as a person passes
through the various stages of sleep and to determine what type of sleep the person has
entered (Aserinsky & Kleitman, 1953).
A person who is wide awake and mentally active will show a brain-wave pattern
on the electroencephalogram (EEG) called beta waves. Beta waves are very small and
very fast. As the person relaxes and gets drowsy, slightly larger and slower alpha waves
appear. The alpha waves are eventually replaced by even slower and larger theta waves.
In the deepest stages of sleep, the largest and slowest waves appear, called delta waves.
Before moving on to the topic of the stages of sleep, it is worth mentioning that the
terminology we now use for the various types and stages of sleep has changed in recent
years, replacing older terminology that dated back to the 1960s (Carskadon & Dement,
2011; Iber et al., 2007; Rechtschaffen & Kales, 1968). If you find yourself reading older
sleep research and see terms like REM (now R), NREM (now N), or four stages of NREM
sleep instead of the three stages we will examine shortly, it is due to this change in the
guidelines set forth by the American Academy of Sleep Medicine (Iber et al., 2007).

sleep deprivation

any significant loss of sleep, result-

ing in problems in concentration and

irritability.

In one study, researchers found that air-

traffic controllers, such as the man pictured

here, were significantly more impaired

in performance after working an 8-hour

midnight shift as compared to a day or

evening shift of equal length (Heslegrave &

Rhodes, 1997).

delta waves

long, slow brain waves that indicate

the deepest stage of sleep.

theta waves

brain waves indicating the early stages

of sleep.

alpha waves

brain waves that indicate a state of

relaxation or light sleep.

non-REM (N, NREM) sleep

any of the stages of sleep that do not

include REM.

rapid eye movement sleep (R, REM)

stage of sleep in which the eyes move

rapidly under the eyelids and the per-

son is typically experiencing a dream.

beta waves

smaller and faster brain waves, typi-

cally indicating mental activity.