Understanding Psychology (10th Ed)

Applying Psychology 
in the 21st Century
Let Me Sleep on It: The Role of 
Sleep in Memory and Thinking
“Let me sleep on it. And I’ll give you an 
answer in the morning.”
As the popular song lyric suggests, lay-
people and scientists alike have long sus-
pected that sleep plays an important role in 
thinking and memory—but what that role 
might be has been less than clear. One idea is 
that a process called memory consolidation 
occurs during sleep. While we’re awake, our 
brains store information from our experi-
ences throughout the day in the hippocam-
pus region. But for long term storage, those 
memories need to be relocated to the cortex, 
where connections are made between the 
new information and what we already 
know. This process helps us to make better 
sense of the new information and to retain 
it—and it may be facilitated by sleep, when 
the infl ux of new information slows to a 
trickle (Cai et al., 2009; Gilestro, Tononi, & 
Cirelli, 2009).
Recent studies are shedding light on 
how memory consolidation works. In one, 
participants memorized a long list of word 
pairs immediately before they went to 
sleep. As soon as they reached the deepest 
stages of sleep, researchers used electrodes 
to stimulate very slow brain waves in 
some of the participants. The participants 
whose brain waves were altered in this 
way showed better recall for the word 
pairs the next morning. The researchers 
theorize that these slow brain waves im-
proved memory storage by strengthening 
the connections between neurons (Ver-
leger et al., 2008).
Another study showed how sleep is in-
volved in thinking as well as memory. The 
researchers gave participants a puzzle that 
involved performing a set of seven opera-
tions on a set of numbers, with the outcome 
of the seventh operation as the fi nal answer. 
The participants were given a series of 
these puzzles using different number sets, 
and they were instructed to fi nd the an-
swers quickly. What the participants didn’t 
know was that there was a “trick” to the 
puzzles: the fi nal answer was always the 
same as the outcome of the second opera-
tion. If they realized this trick, they could 
skip most of the work and give the fi nal an-
swer much more quickly.
The question was whether “sleeping on 
it” would help participants achieve this 
insight—and it did. Participants who 
worked a set of puzzles before sleeping and 
then worked another set the next morning 
were almost three times more likely to dis-
cover the trick than were participants who 
took a long break between puzzle sessions 
but did not sleep (Stickgold & Wehrwein, 
2009; Yordanova et al., 2008).
This, and other fi ndings like it, suggest 
that sleep plays an important role in help-
ing us to analyze and make meaning of 
our waking experiences. “Sleeping on it,” 
then, may turn out to be a reasonable 
strategy for coming to solutions for our 
problems.
• Why do you think memory and thinking may be improved by sleeping?
• How could students make use of memory consolidation while sleeping to improve 
their test performance?
RETHINK
Does sleeping help us to remember more 
eff ectively?
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