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Module 1.5b

Young Adults
REM sleep increases
Awake as night progresses Figure 1.5-7
The stages in a typical TEACH 1.5-5
REM night’s sleep
People pass through a Enrichment
Stage 1 multistage sleep cycle several
times each night. As the night Explain to students that REM is also
Stage 2 goes on, periods of deep sleep
diminish and, for younger known as emergent stage 1 sleep.
adults, REM sleep increases.
Stage 3
As people age, sleep becomes As we go through the sleep cycle
more fragile, with awakenings
1 2 3 4 5 6 7 8 being more common among each night, the body will start with
Hours of sleep older adults ( Kamel & Gammack, the twilight sleep of stage 1 and move
2006 ; Neubauer, 1999 ).
Older Adults into deeper, slow-wave sleep
patterns. When the body cycles back
Awake
up to stage 1, it again experiences
REM
AP Exam Tip brain waves similar to those of
®
Stage 1
stage 1. However, this time it is in
Stage 2 Study this cycle of sleep care-
fully. One common mistake that REM. So, while the brain appears
Distributed by Bedford, Freeman & Worth Publishers. Not for redistribution.
students make is to believe that
Stage 3 to be coming out of sleep every
REM sleep comes directly after
deep Stage 3 sleep. As you can
1 2 3 4 5 6 7 8 see, it does not. Generally, Stage 2 90 minutes, it is actually cycling into
Hours of sleep follows Stage 3; then comes REM. emergent stage 1 or REM sleep.
This clarification will help for the
®
AP exam.
Copyright © Bedford, Freeman & Worth Publishers.
during REM sleep. Neuroscientists have also identified brain regions that are active during
dreaming, which enables them to detect when dreaming occurs ( Siclari et al., 2017 ).
What Affects Our Sleep Patterns?

How do biology and envir
ns?
1.5-6 How do biology and environment interact in our sleep patterns?

1.5-6
onment interact in our sleep patter

True or false? “Everyone needs 8 hours of sleep.” False. Newborns often sleep two-thirds of
their day, most adults no more than one-third (with some thriving on fewer than 6 hours AP Science Practice
®
nightly, while others slumber 9 or more hours). But there is more to our sleep differences Research PRACTICE
than age. Some people are awake between nightly sleep periods — sometimes called “first
sleep” and “second sleep” ( Randall, 2012 ). And some find that a 15-minute midday nap is Having a huge sample size, such as Research Methods & Design
1.3 million people, allows research-
as effective as another hour of nighttime sleep ( Horne, 2011 ). ers to easily generalize their findings
Sleep patterns are genetically influenced ( Hayashi et al., 2015 ; Mackenzie et al., 2015 ). to the intended population — (SP 2)
One analysis of 1.3 million people identified 956 genes related to sleep patterns such as in this case, all people. (5 minutes) Ask students to
insomnia ( Jansen et al., 2019 ). Another identified genes associated with being a morning explain why having a very large
person ( Jones et al., 2019 ).
Sleep patterns are also culturally, socially, and economically influenced. In Britain, CULTURAL sample size allows researchers to
Canada, Germany, Japan, and the United States, adults average 7 hours of sleep on work- AWARENESS more easily generalize their results
days and 7 to 8 hours on other days ( NSF, 2013 ). Earlier school start times, more extra- While the function and purpose of to the population. They should
curricular activities, and fewer parent-set bedtimes lead American adolescents to get less sleep (which we will discuss later in
sleep than their Australian counterparts ( Short et al., 2013 ). Stress, including the experience this unit) transcend culture, you can mention that averages based on
see here that our beliefs and values
of discrimination or poverty, can also disturb sleep ( Johnson et al., 2018 ; Mai et al., 2019 ; about sleep are heavily influenced by many cases are more precise
Vancampfort et al., 2018 ; Yip et al., 2020 ). our culture.
than averages based on a few.
More (randomly sampled) cases
Sleep: Sleep Stages and Theories Module 1.5b 97 make the sample’s estimate more
precise. Larger samples also make
for a more replicable study—one
that will find a similar estimate the
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next time.

Sleep: Sleep Stages and Theories Module 1.5b 97

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