Relationship between Sleep Quality and Visual Short-Term Memory

in Young Adults

Haoyue Li

University of California, San Diego, La Jolla, California, 92093, U.S.A.

Keywords: Sleep Quality, Visual Short-Term Memory, Young Adults.

Abstract: Modern studies have indicated an active role of sleeping in memory consolidation. To further explore the

relationship between them, the present study tested the relationship between sleep quality and visual short-

term memory (VSTM) function. The study was conducted via online surveys and targeted at people aged 18

to 30 years old. The survey contained three main sections, basic information, sleep quality questionnaire, and

VSTM tests. There are three questions asking age, gender, and education level of the basic information

section. The Pittsburgh sleep quality index (PSQI) questionnaire was utilized to assess sleep quality, and

global PSQI score was calculated according to the given PSQI calculation model. VSTM tests contain

questions with pictures showing squares of different colors and randomly ask the color of a specific square.

A total of 82 responses were used for data analysis. Most participants included are college students. A few of

them are grad students. The results implicate that no association between sleep quality and VSTM function in

younger adults was found in the present study. After comparison between good and poor sleepers, no

significant difference in VSTM performance was discovered. Furthermore, after comparing the VSTM

performance between females and males, no significant difference was found in the present study. The results

from the present study might offer new insight for the relationship between sleep quality and short-term

memory and thus suggests new direction for clinical treatment to certain mental diseases.

1 INTRODUCTION

Sleeping plays an important role in many aspects. It

is believed that sleeping allows our body and mind to

recharge, helping us to stay healthy. Studies have

shown that sleep deprivation could cause enormous

problems in human healthy. From basic level, sleep

deprivation could increase response time, slowing

down the reaction speed. Regarding to higher level

cognition function, such as memory, perception, and

executive functions, even though there are

disagreements on how sleep loss could affect them,

emerging evidence have suggested that sleep loss

would impair certain functions, including learning,

memory, and especially cognitive systems that rely on

emotions (Killgore 2010). In human bodies, we have

a circadian rhythm, an internal 24-hour clock that

regulates our sleep cycle. For young adults, it’s

recommended to have 7 to 9 hours for sleep.

According to National Sleep Foundation, sleep

quality is defined as the measurement of how well

you are sleeping. There are several factors used to

determine sleep quality, including sleep latency, sleep

waking, wakefulness, and sleep efficiency. In the

present study, the Pittsburgh sleep quality index

(PSQI) used to assess sleep quality contains all

factors mentioned above.

Memory is the ability to both preserve and recover

what we have learned and experienced. There are

three general steps of memory: encoding, storage, and

retrieval. There are two main kinds of memory, short-

term memory which lasts seconds to hours and long-

term memory which could last for years. The present

study mainly focuses on short-term memory,

especially VSTM. Short-term memory (STM) could

be considered as a temporary storage system which

usually lasts about 20 seconds and only holds a small

amount of information. It’s commonly believed that

for human, the STM capacity is 7±2. VSTM is

defined as the memory system that stores visual

information for seconds. Previous studies have

suggested that the capacity of VSTM is 4 items, but

newer findings have indicated that the capacity could

be set by both the information contained and the

number of objects (Alvarez, Cavanagh 2004). In the

present study, pictures with 8 squares of different

484

Li, H.

Relationship between Sleep Quality and Visual Short-Term Memory in Young Adults.

DOI: 10.5220/0011372600003438

In Proceedings of the 1st International Conference on Health Big Data and Intelligent Healthcare (ICHIH 2022), pages 484-489

ISBN: 978-989-758-596-8

colors were presented for a few seconds as visual

stimulus, and a random square will be asked about its

original color to test VSTM function.

The relationship between sleeping and memory

has been studied for a long time. Early studies believe

sleeping functions as a passive role in memory

consolidation by protecting them from external

stimulus, modern studies have shown sleeping plays

an active role since memory undergoes processes for

consolidation (Rasch, Born, 2013). Previous study

has suggested that sleep deprivation could impair

short-term memory of normal objects (Li, Wu, Shao,

Liu 1991).

Inspired by all these information, the current study

wants to further examine the association the effect of

sleep quality on visual short-term memory (VSTM).

The hypothesis is that there is association between

sleep quality and VSTM function, and poor sleep

quality would result in worse VSTM performance.

The current study uses Pittsburgh sleep quality index

(PSQI) questionnaire to test sleep quality and 12

questions containing squares of different colors to test

VSTM function among around 80 Chinese young

adults. It’s hoped that by studying the relationship

between sleep quality and VSTM, this study could

help better answer the question that if sleep could

improve STM. In addition, from clinical aspect, this

study might have potential for developing more

effective treatment to mental diseases. Sleeping

disturbances are more common among patients with

mental diseases that have symptoms of memory

disorder than in general population. One such disease

is schizophrenia, as data has shown that about 50-

80% patients reported sleep problems while in

general population, the number is approximately 30%

(Cohrs 2012). Currently, many treatments of

schizophrenia thus usually tend to increase total sleep

time and sleep efficiency (Cohrs 2012). The result of

the present study might provide new insight into

clinical treatment.

2 METHODS

In this study, I conducted online survey designed

through Qualtrics to test the sleep quality and VSTM

function. The online survey contained three main

parts: basic information, sleep quality questionnaire,

and VSTM tests. The whole survey is anonymous.

For the basic information part, participants were

asked three questions: age, gender, and education

level. The PSQI questionnaire is used to test the sleep

quality. The Pittsburgh sleep quality index (PSQI)

questionnaire is a self-rated questionnaire that covers

a 1-month time interval (Buysse, Reynolds, Monk,

Berman, Kupfer 2002). The final global PSQI score

was calculated based on the given PSQI calculation

model. A lower global PSQI score indicates a better

sleep quality. The last part of the online survey is the

VSTM function tests. There is a total of 12 questions

in each survey. For each question, there will first be a

picture with 8 squares at different positions with

different colors. This colorful picture would appear

for 5 seconds. After the 5 seconds, the picture would

automatically disappear according to the design of the

survey, and another picture will be shown with a

multiple-choice question to the participants. The

second picture has the same 8 squares at the same

positions but with no color. An arrow points at a

random square in the second picture, and the

participants will be asked to choose the color of the

indicated square. All positions and color of the

squares and the indicated square in each question are

random. Details of those pictures are shown below

(Figure 1). Each question is counted as 1 point for the

final performance score. For example, if a participant

gets 4 questions right, his or her performance score

will be 4 out of 12 points.

Figure 1: A sample of the pictures used in the VSTM test. The first picture (on the left) will first appear for 5 seconds. After

this short time, the second picture (on the right) will appear with the question asking about the original color of the pointed

square.

Relationship between Sleep Quality and Visual Short-Term Memory in Young Adults

485

The link to this survey was published online

through social media. In order to better control the

noises of other factors that could potentially influence

the short-term memory function, only people aged

between 18 and 30 years old were allowed to

complete the survey. In the end, this survey got a total

of 86 responses. But for the final data analysis, only

82 responses were used. This is because some

responses had very ambiguous answers so that their

global PSQI score could not be accurately

determined. Some responses were incomplete. There

was also one response that has 0 scores for the

performance score, and it is doubted that this person

didn’t seriously take the survey. Therefore, to make

the research more powerful, only 82 responses were

utilized in the analysis.

In terms of the data analysis, descriptive data,

mean and standard deviation, were calculated for the

age, PSQI score, and performance score. Shapiro test

was used to test the distribution of the PSQI score and

performance score. Spearman correlation test was

used to determine if there’s a significant association

between sleep quality and VSTM function. To better

determine if certain parameter could affect the VSTM

function, a two-sided Mann-Whitney test was used to

test the significance of difference in the VSTM

performance. The threshold is set at p = 0.05 for the

significance. All these tests were performed using R.

3 RESULTS

The survey finally got 82 complete responses. Based

on their answers to the question of their education

level, most participants are undergraduate students.

Several of them are grad students. One participant is

currently working. For all responses, mean and

standard deviation of the age, the global PSQI score,

and the performance score were calculated. The

results are shown in the below table (Table 1).

Table 1: mean and standard deviation of age, PSQI score,

and performance score for the whole dataset.

mean sd

age 21.57 (yrs) 2.84 (yrs)

PSQI score 5.21 2.96

Performance score 7.59 2.55

Shapiro test was performed on the PSQI score and

the performance score to test the distribution of these

data. The p-values from this test are shown in the

table below (Table 2). Both p-values are smaller than

the threshold, 0.05, therefore the distributions of these

data are not normal. This indicates that spearman test

should be used for the correlation test and Mann-

Whitney test should be used to test the significance of

difference.

Table 2: p-values from the Shapiro test on the PSQI score

and the performance score of the whole dataset.

p-value

PSQI score 5.268E-5

Performance score 0.01192

The main goal of the study is to determine if sleep

quality is related to the VSTM function. Therefore, a

correlation test was performed to examine if there’s

any association between them. Since the Shapiro test

gave p-values smaller than 0.05, indicating that the

distributions of the PSQI score and the performance

score are not normal, the spearman method was used

for the correlation test. The correlation coefficient is

-0.0839, and the p-value is 0.4536. The correlation

coefficient is slightly negative, implicating that a

lower PSQI score might be associated with a better

performance score. This is expected since a lower

PSQI score means a better sleep quality. However, the

p-value is larger than 0.05, indicating a non-

significant correlation between sleep quality and

VSTM performance. A scatterplot of VSTM

performance vs. PSQI score was also drawn (Figure

2). From the scatterplot, we can that the distribution

is relatively random, which could further support the

conclusion from the correlation test.

Figure 2: scatterplot of visual short-term memory

performance score vs. PSQI score. The distribution in this

scatterplot is relatively random.

ICHIH 2022 - International Conference on Health Big Data and Intelligent Healthcare

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To better determine if sleep quality could affect

VSTM function, I separated the data into two groups

based on the PSQI score. According to Buysse et al.,

a global PSQI score greater than 5 yielded both high

diagnostic sensitivity and specificity (both over 80%)

in distinguishing good and poor sleep quality

(Buysse, Reynolds, Monk, Berman, Kupfer 2002).

Thus, I categorized participants with a PSQI smaller

than 5 into the good sleep quality group and

participants with a PSQI greater than or equal to 5 into

the poor sleep quality group. After categorizing the

data, good sleep quality group has 37 participants,

and the poor sleep quality group has 45 participants.

Then I ran the Shapiro test on the PSQI score and

performance score of both groups. The p-values of the

PSQI score of both groups are smaller than 0.01, way

smaller than the threshold. The p-value of the

performance score of the good sleep quality group is

0.01485, and the p-value of the poor sleep quality

group is 0.5213. Based on the p-values, most data are

not normally distributed, thus the Mann-Whitney test

should be performed to compare the performance

difference between the two groups.

In order to examine the significance of the

difference, mean and standard deviation of the

performance score were first calculated. The good

sleep quality group has a mean of 7.65 with a standard

deviation of 2.93, while the poor sleep quality group

has a mean of 7.53 with a standard deviation of 2.22.

The Mann-Whitney test gave a p = 0.5019, larger than

0.05. Therefore, the difference in the VSTM

performance between the two groups is not

significant.

To test if gender could be a factor affecting the

VSTM function, data were separated into the female

and male groups based on their answers. There are 64

females and 18 males. The mean and standard

deviation of the PSQI score and the performance

score of these two groups were calculated as shown

in the table below (Table 3&4). Since the group sizes

differ greatly, the Mann-Whitney test was performed

to test the significance of the performance difference.

The test gave a p = 0.7052, greater than 0.05.

Therefore, no significant performance difference was

found between the two genders.

Table 3: mean and standard deviation of the PSQI score and

the performance score for the female group.

Female group mean sd

PSQI score 5 3.07

Performance

score

7.67 2.54

Table 4: mean and standard deviation of the PSQI score and

the performance score for the male group.

Male group mean sd

PSQI score 5.94 2.51

Performance

score

7.28 2.63

4 DISCUSSION

Based on the results from the data analysis, three

conclusions could be reached. First, there’s no

association found in this study between sleep quality

and VSTM function. Second, sleep quality might not

affect VSTM function. Third, gender might not be a

factor that influences VSTM function. Some previous

studies have reached a similar conclusion as the

present study. One study conducted by several

undergraduate students at Georgia college tested 25

individuals for their sleep quality short-term memory

function. Their study also used the PSQI for testing

sleep quality and word recall tasks for the short-term

memory function. They found no correlation between

sleep quality and the number of words recalled and no

significant difference in the number of words recalled

by males and females (Holcomb, Raisin, Gravitt,

Herrick, Mitchell 2016). This could reflect the results

of the present study.

In another study conducted by Xie et al. (2019),

sleep quality, working memory, and depressed mood

were assessed. They used a short-term recall task and

measured both the capacity and the precision of the

working memory. They found that poor sleep quality

could reduce the short-term memory capacity but not

the precision (Xie, Berry, Lustig, Deldin, Zhang

2019). This conclusion could mirror the results in the

present study. In the present study, the performance

score of the VSTM tests is the number of questions

the participant answered correctly. This could be

considered as a measurement of the precision of

short-term memory. In other words, the conclusion of

the present study could be interpreted as no

association found between the sleep quality and the

precision of VSTM and no significant influence in the

VSTM precision by sleep quality found based on the

data, which is the same result as the previous study.

This might also indicate that for future interest, the

relationship between sleep quality and short-term

memory capacity could be studied.

Even though there are some studies indicating that

there might not be association between sleep quality

and short-term memory function, many previous

studies have suggested the opposite. An early study

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487

conducted by Li et al. (1991) examined the sleep

quality and short-term memory with several tasks and

proved the importance of sleep in short-term memory

function. The results from their short-term memory

tests showed that sleep deprivation caused obvious

drops in the score (Li, Wu, Shao, Liu 1991). They

further conducted REM sleep deprivation using rat

model and found the duration of the deprivation is

potentially related to the strength of the impact on the

short-term memory function by sleep deprivation. In

addition, the team assessed the sleep quality and

found that good sleepers had remarkably higher

scores on digit span test than poor sleepers (Li, Wu,

Shao, Liu 1991). However, for digit symbol, cube

figure, and digit cancellation tests, no significant

differences were found between the two groups (Li,

Wu, Shao, Liu 1991). This finding might to some

extent support the results found in the present study.

The VSTM test in the present study only contains

squares, which is similar to the cube figure test. Thus,

it might be reasonable that no significant relationship

between sleep quality and short-term memory was

found. However, it might be worthy for future studies

to investigate the reason why certain tests do not

reveal the relationship.

The current study found no significant difference

in VSTM function between two genders. One early

study about gender difference and short-term memory

function somehow provided similar result. The study

tested on 1279 individuals, 637 males and 642

females, aged from 5 to 19 years old and performed

14 subsets of the Test of Memory and Learning

(TOMAL) on all individuals (Lowe, Mayfield,

Reynolds 2003). With this large sample size, the study

revealed similarities between two genders on the

VSTM tests. Even though a few tests showed minor

differences, there were no consistent pattern found,

and the magnitude of those differences are small,

indicating there might be no gender difference in

VSTM function (Lowe, Mayfield, Reynolds 2003).

However, the study revealed that gender difference

might play a role in other kinds of short-term memory.

The study concluded that females scored higher on

two verbal memory tests while males scored higher

on spatial memory tests. These findings might offer

new future directions in terms of gender effect on

certain short-term memory function.

The main goal of the present study is to determine

the relationship between sleep quality and VSTM

function. The conclusion rejected the original

hypothesis which proposed that worse sleep quality

might be associated with poor VSTM function.

However, as stated above, many previous studies

have found such effect on short-term memory

function. One potential reason for this mix might be

age. Many studies have illustrated that age could

affect short-term memory function, and usually the

short-term memory function peaks at young

adulthood. One such study tested on younger children

(10 to 12 years), teenagers (13 to 15 years), younger

adults (20 to 25 years), and older adults (70 to 75

years) and concluded that item-bindings, closely

related to short-term memory function, are

functioning better in teenagers and young adults than

children and older adults (Fandakova, Sander,

Werkle-Bergner, Shing 2014). Some studies also have

shown similar conclusion and proved from

neurobiology aspect. One such early study claimed

that the binding process and the top-down control,

related to posterior and frontal brain regions and their

interactions with the whole neural network,

experience large changes across the lifespan as both

grow mature until young adulthood and decline as age

increases, leading to the peak of short-term memory

function in young adulthood (Sander, Lindenberger,

Werkle-Bergner, 2012). In the present study, most

participants could be considered as young adults.

According to the above findings, the participants

included in the present study might exert ceiling

effect, all performed high short-term memory

function regardless of sleep quality. Therefore, the

effect of sleep quality might be reduced so that no

association was found.

There are certain limitations in the present study

as well. First, all participants are aged 18 to 30 years

old. Most of them are college students. As discussed

above, these participants could exert a ceiling effect

on the study, reducing the power of sleep quality on

short-term memory function. This also constrains the

scope and the application of this study, limiting it to

be only applicable to young adults. This also

introduces the second limitation of the present study.

The survey of this study took place during the

summer break, during which students’ sleep quality

might not strongly influence students’ behavior due to

many other factors. This “summer break” limitation

can potentially decrease the association between

sleep quality and short-term memory function. To

improve it, future studies could conduct at another

time period to avoid summer break. The third

limitation is due to the accessibility of research tools.

All data of the present study were collected via an

online survey, and no monitor was conducted when

participants finished the survey. Therefore, if

participants cheated, for example, taking pictures

during the VSTM tests to help them remember the

color, researchers could not know the truth. Thus,

their performance score might not reflect their real

ICHIH 2022 - International Conference on Health Big Data and Intelligent Healthcare

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VSTM function. Improvement could be made by

giving the survey in person to better control

environmental influence. In addition, since the

VSTM tests were designed personally by the

researcher, the professionality might not be fully

guaranteed. For future studies, if possible, more

professional tests should be utilized. Fourth, there

might be response bias in the present study. The link

to the survey was published online through social

media. As a result, only people who have social media

and are interested in the survey would complete the

survey, resulting in response bias. Therefore, the

result of the present study might not be able to apply

generally. Finally, self-response bias might appear in

the present study. The PSQI questionnaire utilized to

assess sleep quality is a self-rated questionnaire. The

global PSQI score is calculated only based on the

response from the participant. Even though the

calculation model usually counts component scores

based on a range of the answer to be more general, the

inaccuracy of responses still could affect the global

PSQI score, thus further affecting the conclusions.

For future study, the relationship between age,

sleep quality, and short-term memory function could

be studied by increasing the age range of the sample.

Researchers could also have several groups of

different ages and make comparisons between them.

In addition, despite the fact that no relationship

between sleep quality and VSTM were found, there

might be relationship between sleep quality and other

kinds of short-term memory. Thus, those

relationships could be studied due to interest by

including various kinds of short-term memory tests,

such as auditory word recall tasks. Finally,

understanding the relationship between sleep quality

and short-term memory function might shed light on

future treatment for mental diseases. As mentioned in

the introduction section, some mental diseases have

symptoms of sleeping disturbances associated with

memory disorder. Thus, future studies could explore

which factor of sleeping is related to the disease in

order to develop clinical treatment.

5 CONCLUSIONS

The present study mainly investigated the

relationship between sleep quality and VSTM

function among young adults and included analysis of

gender effect as well. Three conclusions are reached

in the present study. First, there’s no association

found in this study between sleep quality and VSTM

function. Second, sleep quality might not affect

VSTM function. Third, gender might not be a factor

that influences VSTM function. These results might

indicate that further examinations are required to

determine the relationship between sleep quality and

VSTM. Based on findings from previous studies,

future studies could also investigate sleep quality and

other kinds of short-term memory, gender effect, and

effect of different factors of sleep on short-term

memory function to develop clinical treatments for

mental diseases. Since sleep and memory are closely

related to many mental diseases, results from the

present study might suggest new direction in future

effective clinical treatment.

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