Available online at:
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J Camosun Psyc Res. (2020). Vol. 2, pp. 24-29.
Submitted Fall 2019; accepted June 2020.

The effect of sleep on memory.
Authors: An Ton*, Devyansh, Amanpreet Kaur, and Gurleen Kaur
Supervising Instructor: Michael Pollock, Psyc 215 (“Biological Psychology”)
Department of Psychology, Camosun College, 3100 Foul Bay Road, Victoria, BC, Canada V8P 5J2
*Corresponding author email: glawcc.nit@gmail.com

ABSTRACT
The present studies investigated the memory retention of words and its relationship to sleep.
The studies involved 4 college students and the first study followed a series of longitudinal
within-subjects correlational assessments of hypotheses relating overnight memory retention to
the following three other variables: hippocampal changes during sleep, quality of sleep, and
quantity of sleep. After finding the highest correlation between quantity of sleep and memory
retention, the causal relationship between these two variables was further experimentally tested.
Sleep quantity was manipulated by randomly assigning each day across a two-week period to
one of two possible conditions: a day with a 3-hour nap versus a day with no naps. The results
of the experiment supported the hypothesis that increases in the amount of sleep result in a
greater memory retention. These results are of importance for college students in maintaining a
healthier academic profile and suggest that greater memory retention is capable by having
adequate sleep.
1. Introduction
Humans spend about one-third of their
lives sleeping (if the average night’s sleep is
about eight hours). Many scientists raise
questions about the occurrence of sleep in
our daily life. Why do we need sleep? What
is the role of sleep? Many studies have been
conducted and researchers have found many
advantages of sleep in everyday life, from
energy conservation to tissue restoration. In
recent studies, scientists have found an
additional advantage of sleep: sleep helping
in memory retention. A common complaint
from many students, though, is that after
studying all night they were not able to
perform their best in exams and didn’t get
good marks as they could not recall many
parts of what they had previously learnt.

This type of complaint has led many
researchers to conduct studies in order to
find the relationship between sleep and
memory retention.
Many of these studies have compared
individuals who had a good amount of sleep
at night with those who had disrupted sleep
at night to find the effect of sleep on
memory. One of these studies was by
Scullin (2013) in which he examined in
young and old adults how changes in slow
wave sleep and episodic memory are related
across different sleep-wake conditions: 12hr wake, 12-hr sleep, and 24-hr (night-tonight) sleep groups. He found a significant
correlation of equal sleep and wake cycles
with memory retention in younger adults but
the contrasting results and even a negative
correlation for the same variables in older
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adults, highlighting some weakening of the
sleep–memory linkage over time. However,
it is possible that that this could be the result
of the different amounts of sleep that people
of different ages have.
To investigate the relationship between
the quantity of sleep and memory, Potkin &
Bunny (2012) had a list of 10 words pairs
administered three times in immediate
succession and then sleep and non-sleep
groups were tested 12 hours later. They
found that increased quantity of sleep
improves memory retention and they argued
that this memory consolidation is
independent of the time of the day in which
it occurs. Hence, the present study
hypothesized that as the quantity of sleep
increases, memory retention increases.
A study by Jegou et al. (2019)
investigated the effect of hippocampal
activity during sleep on retention of words
using EEG and fMRI. The experiment
included two visits, each had three sessions
taking place during the first half of the day:
a learning session, a 3-hour maximum sleep
session and a post sleep recall session. The
results indicated that there is a positive
correlation between the change between fast
spindles and slow spindles during sleep in
the right hippocampus during the learning
night (as compared with the control night)
and the post-pre sleep change in recall
performance.
2. Methods
2.1 Participants
Four college students participated in the
studies. The students were recruited from
Camosun College, Victoria and ranged from
ages 18 to 21. There were 3 females and 1
male in the present study.

2.2 Materials
The materials used in the current studies
involved lists of 15 randomly generated
words (sourced from
www.randomwordgenerator.com) which
were not repeated on any day of
measurement and consisted of different 4 to
6 letter words. The words were different for
each individual but involved similar length
words.
2.3 Procedures
2.3.1 Correlational Study Procedure
All correlational studies happened in the
same duration of 12 days. Each night, before
going to bed, each participant memorized 15
words that had been randomized by the
website. After waking up, the subjects
recorded the number of words that they
correctly recalled. For the hippocampus
hypothesis, the participants also recalled and
recorded the number of words that were
correct before sleep and subtracted this
number from the number of words recalled
post sleep. They then rated the quality of
sleep on that night on the scale of 1 to 10 on
how satisfying they were. Their
hippocampal activity during the night was
measured by how many dreams related to
locations there were and how clear they
were on the scale of 0 to 100. The number of
hours the participants slept was also
recorded each night.
2.3.2 Experimental Study Procedure
The participants generated a random list
of words before starting each experimental
condition and control condition trial. In the
experimental condition, during a 12-day
period, the participants remembered the list
of words and then slept for 3 hours from 12
PM to 3 PM for 6 days as compared to the
control condition of having no sleep during
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the same time period for 6 days. A box was
prepared for each participant with 6 folded
pieces of paper with the word “control” and
another 6 with the word “experimental”.
Each day, the subjects would shake the box
and pick one indicating which condition of
that day was. The participants when in
control condition involved themselves in
their routine daily chores for the same
duration as in experimental condition. After
3 hours the subjects recalled as many words
as they could from the list and then scored
themselves based on the number of correctly
remembered words from the list.

Figure 1). There was also a statistically
significant correlation between quantity of
sleep and memory retention (r = 0.47, p =
0.004, see Figure 2). For the hypotheses of
hippocampal response changes during sleep
and overnight changes in recall
performance, there was no statistically
significant correlation founrd (r = 0.06, p =
0.750, see Figure 3). Both the pooled raw
data and pooled standardized data of the
three studies shows the same results. The
quantity of sleep and memory retention
received the highest correlation value and
hence became the experimental hypothesis.

3. Results

3.2 Experimental Study Results

3.1 Correlational Study Results

The mean of the number of correct words
recalled in the 3-hour nap condition was 9
(SD = 1.04) and in the no-nap condition the

There was statistically significant
correlation (r = 0.35, p = 0.035) between
quality of sleep and memory retention (see

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Ton, Devyansh, Kaur, Kaur - J Camosun Psyc Res. (2020). Vol. 2, pp. 24-29.

mean value was 6.75 (SD = 1.57). This data
was analyzed using an independent t-test
and the results were significant, t(46) = 3.75,
p = .000 for the pooled raw data (see Figure
4) and t(46) = 4, p = .000 for the pooled
standardized data. This suggests that the
increase in the amount of sleep resulted in a
greater number of words recalled.
4. Discussion
While a positive correlation was found
between memory retention and both the
quality and quantity of sleep, no statistically
significant relationship was found between
hippocampal activity during sleep and
changes in recall performance. The results of
our experimental study also supported a
causal role of increased sleep quantity upon
improvements in memory retention.

These findings are in line with other
previous studies on quality and quantity of
sleep and memory retention. Potkin and
Bunney (2012) found that long-term
memory was improved in the group that was
tested following a sleeping period as
compared to the group in which sleep was
omitted. Moreover, the effect of sleep on
memory retention was also dependent on the
quality of sleep, where recall performance
has been found to be improved if people
have good sleep-behaviour (Scullin, 2013).
However, in contrast to Jegou et al.
(2019), whose findings suggested a positive
correlation between hippocampal response
during sleep and the post-pre sleep change in
recall performance, our study found that the
correlation was not statistically significant.
This difference was possibly caused by the
difference in measurement of retention,
which was that some subjects only
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Ton, Devyansh, Kaur, Kaur - J Camosun Psyc Res. (2020). Vol. 2, pp. 24-29.

considered the number of correctly recalled
words post sleep instead of the difference
between number of words recalled post
sleep and pre sleep. To test the hypothesis
that an increase in hippocampal response
during sleep will lead to an improvement in
overnight change in recall performance, the
group were to measure the discrepancy by
subtracting the amount of correct words
recalled before sleep from the number of
words after sleep. However, some subjects
just used the data from after waking up,
possibly leading to differences in the
significance of result.
The present study only involved
experimenting on college students’ memory
retention of random words. The study
involves small sample size with limited
demographic representability and limitation
on the materials, as information that needs to
be memorized is not always limited to
randomly generated words.
Based on the group finding, the amount
of sleep a person gets has a positive effect
on their memory retention of information.
These results have many important
implications, mainly on the importance of
having a balance life and a healthy sleep
schedule. Students should be encouraged to
have enough sleep every night to maximize
study ability. The results of this study might
also enhance our understanding of academic
performance and its relationship with sleep
disorders such as insomnia.

Potkin, K. T., & Bunney, W. E., Jr. (2012).
Sleep improves memory: The effect of
sleep on long term memory in early
adolescence. PLoS ONE, 7(8). https://doiorg.libsecure.camosun.bc.ca:2443/10.137
1/journal.pone.0042191
Scullin, M. K. (2013). Sleep, memory, and
aging: The link between slow-wave sleep
and episodic memory changes from
younger to older adults. Psychology and
Aging, 28(1), 105–114.
https://doi.org/10.1037/a0028830

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