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The effects of lunch time napping on habitual nappers’ mental work efficiency in the afternoon and early

Authors:
Vol.1, No.4, 284-289 (2009)
doi:10.4236/health.2009.14046
SciRes
Copyright © 2009 Openly accessible at http://www.scirp.org/journal/HEALTH/
Health
The effects of lunch time napping on habitual nappers’
mental work efficiency in the afternoon and early
evening: an empirical study from China
Guang-Jin Zhang
1
, Fei-Fei Sun
2
, Jian-Qiao Liao
3
1
Politics and Law School, China University of Geosciences, Wuhan, China; hbzgj@126.com
2
Faculty of Foreign Languages, Jiangxi University of Finance and Economics, Nanchang, China
3
Management School, Huazhong University of Science and Technology, Wuhan, China
Received 27 September 2009; revised 5 November 2009; accepted 11.November 2009.
ABSTRACT
30 college students who have the habit of lunch
time napping (LTN) participated in experiments
under two different conditions: Having lunch
time napping and not having lunch time napping.
They were asked to complete three tasks in-
cluding vigilance reaction, short-term memory,
addition arithmetic; their performance was re-
corded automatically by computer during 3 dif-
ferent periods in the afternoon and early eve-
ning. The analysis about the experimental data
showed that: as for habitual nappers, midafter-
noon nap zone existed, LTN played a very im-
portant role in overcoming it, and did great help
in enhancing their vigilance in the afternoon and
early evening, however, LTN didn’t bring sig-
nificant positive effect to executing complex
tasks (such as short-term memory and addition
task) at the periods of time 16:30-17:30, 20:00-
21:00. Finally, this article discussed the conclu-
sions and its significance.
Keywords:
Lunch Time Napping; Mental Work
Efficiency
1. INTRODUCTION
Lunch time napping is very prevalent in China. The
farmers often take LTN only in summer because they
need avoid the hot sun’s radiation at noon; however,
more and more mental workers also take LTN, moreover,
they usually take LTN all the year round, which can’t be
explained by the weather. An investigation in a univer-
sity found that 71% teachers and 78% students are used
to taking LTN more than 10 months a year; the respon-
dents admitted that they won’t perform well or work
efficiently in the afternoon and evening without LTN.
However, LTN also induced a lot of controversies, some
people think that it leads to low work efficiency for that
the continuity of eight hours work a day is interrupted by
LTN. Besides, LTN extends the time between going to
work and getting off work, especially for those whose
home is far away from work site, such as the work time
of not having HTL is often from 9:00 to 17:00, otherwise,
it is usually from 8:00 to 17:30, which makes people feel
more tired [1]. Dose not having LTN really lead to ha-
bitual nappers’ mental work inefficiency?
To look for the answer from former researches, there
were two difficulties. Firstly, Chinese literature usually
only describes people’s subjective feeling, few of them
studies the effects of LTN based on the actual work per-
formance. Secondly, in most of relative English litera-
ture, the napping time is often in the afternoon or in the
evening, even in a few of researches about LTN, the du-
ration of napping is very short, which is not consistent
with the situation of China. For example, Macchi, Bou-
los and Ranney et al. studied the effects of afternoon nap
on nighttime alertness and performance [2]. McEvoy &
Lack studied the effects of nap (happens in the night
shift) on work efficiency [3]. Mednick, Nakayama and
Cantero et al. studied the restorative effects of afternoon
naps on perceptual deterioration [4]. Backhaus & Jung-
hanns studied effects of afternoon nap on memory ability
[5]. Milner, Fogel and Cote studied the effects of after-
noon nap on motor performance and the moderation ef-
fects of habitual napping between them [6]. Hayashi et
al. studied the effects of both afternoon nap and lunch
time nap on mood, performance and EEG activity [7-8].
Driskell and Mullen made A Meta-Analysis about the
efficacy of naps as a fatigue countermeasure [9]. Almost
all the naps studied mentioned above in the afternoon,
which is the working time in China, the working time in
the afternoon in China is often from 14:00 to 17:30 or
14:30-18:00. LTN is a common phenomenon in China,
and the napping duration is usually as long as 1 hour to
1.5 hours (12:30-13:30 or 12:30-14:00). Therefore, the
context about the western scholars’ researches is far dif-
ferent from Chinese reality, the conclusions of those
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researches can’t be simply applied to practice in China.
For the two pieces of reasons above, this research is to
study the effects of LTN on habitual ‘nappers’ mental
work efficiency in the afternoon and early evening
through experiment.
2. METHOD
2.1. Subjects
30 college students (18 females and 12 males) partici-
pated in the experiment. These subjects have the habit of
lunch time napping, they have lunch time napping at
least 4 times a week, and more than thirty minutes each
time, their night sleep is often from 23:00 to 7: 00, they
are healthy and don’t have the habits of smoking and
heavy drinking. They did not take any drug during the
experiment; meanwhile, all subjects are voluntary and
given payment.
2.2. Procedure
The experiment is a balance intra-group design, that is,
the 30 subjects were simple randomly divided into two
groups with the same number. Each group participated
once in two kinds of condition experimentHaving LTN
and not having LTN), in order to eliminate the possible
influence of the shift experimental condition on work
efficiency in the next day, the two tests under different
experimental condition which each group subjects par-
ticipated in were conducted at one week interval. In par-
ticular, half of the subjects firstly participated in the ex-
periment under the condition of having LTN, and then
took the second test under condition of not having LTN
one week later; the other half took the first test under not
having LTN condition, and then took the second test
under having LTN condition after a week.
In this study, the two kinds of experimental conditions
are having LTN and not having LTN. The former is to let
the subject have lunch time napping in dormitory from
12:30 to 14: 00, and arrive at the lab at 14:25. The later
is to let the subjects arrive at the lab by 12:30, and they
can do anything except taking naps until 14:25. In the
week before the first experiment test and the week in-
terval between the two experiment tests, the subjects
were required to take normal night sleep and lunch time
napping everyday, and to keep daily log so as to be
checked. In order to let the subjects be familiar with and
proficient at the experimental tasks, in the morning of
the day before the first experiment test, all subjects par-
ticipated in the instructions of the experiment and took
15 minutes practice for the three experimental tasks.
Each experiment includes three periods. The first pe-
riod lasts from 14:30 to 15:30, the second period lasts
from 16:30 to 17:30, and the third period is from 20:00
to 21:00. During the experiment, the subjects were not
allowed to leave the laboratory except for having supper
outside, they can read novel, play games or chat in the
laboratory between the three periods. The reason for the
first period design is that most organizations in China
require their employees to start work at 14:30 in summer;
the second period and the third period are to measure the
effects of LTN on work efficiency before off duty in the
afternoon and in the early evening.
In each period of the experiment, all subjects need
accomplish three tasks: vigilance reaction, short-term
memory, addition arithmetic, after each task there will be
five-minute rest. As for the task of vigilance reaction, it
needs the subjects response to 40 signals; as for the task
of short-term memory, it needs the subjects recall 20
groups of English letters; as for the task of addition, it
needs the subjects judge whether right or not about 30
equations of pairs of three-digit number addition. It will
take about one hour to finish all the three tasks.
In order to motivate the subjects to participate in the
experiment seriously, we had clarified that better per-
formance and more payment.
2.3 Experimental Task
This study chose three typical mental workers as the
experimental tasks.
One of the experimental tasks is vigilance reaction.
This experimental task is completed on the computer.
There is a clock designed by the researcher on computer
screen, and the clock is the same as the one in our daily
life. There is only one exception that its second hand
occasionally walked 2 grids, and the requirement for
subjects is to press the “Del” button in low right corner
of the keyboard when the second hand walked 2 grids,
then the computer would automatically record the sub-
ject’s response. During the experimental task, the prob-
ability of second hand randomly walked 2 grids was 0.02,
in other words, the second hand walked 2 grids once
about on the average of 50 seconds, the probability is
very appropriate, for if it is too small, signals appeared
little, it would make subjects divert attention easily; if it
is too large, signals appeared much, this would lead to
the loss of the vigilance reaction characteristic. Since the
second hand walked 2 grids is a random event, so within
30 minutes on each subject’s computer screen, the num-
ber of signals was different, therefore, and the rate of
wrong response was to evaluate the level of vigilance for
the subjects. Here, the rate of wrong response refers to
the total number which is the number of the second hand
walked 2 grids but the subject didn’t press the “Del”
button adds the number of the second hand walked nor-
mally but the subject pressed “Del” button in the propor-
tion of the total number of the second hand walked 2
grids.
The second experimental task is short-term memory.
The earlier research has shown that human short-term
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286
memory capacity is very limited and its storage time is
short, it was considered as the bottleneck of human in-
formation procession. In this task, 20 groups of alphabet
need the subjects recall one by one, and every group of
alphabet consist of 10 letters, 10 letters showed on the
computer screen in succession at a speed of one letter
every two seconds, when the last letter of one group al-
phabet appeared, there were 10 seconds for the subjects
to write the letters just showed on the computer screen
from their memory, the computer will automatically
compare the letters which the subjects wrote down with
the alphabet, the number of the letters recalled correctly
will be taken as the subjects’ short-term memory per-
formance, and the average number of the 20 groups of
letters recalled correctly will be taken as the data to be
analyzed in the following.
The third experimental task is addition arithmetic. The
computer will display an equation of a pair of three-digit
numbers addition on the screen every time, such equa-
tions in total up to 30, some of them are wrong, and
some are right. The task required the subjects to judge
them whether right or not as quickly and accurately as
possible. Pressing the button “enter” on the low right
keyboard when the equation is right, and pressing the
button “ctrl” on the low left keyboard when the equation
is wrong, the next equation appeared immediately when
the subjects completed pressing key, the computer will
automatically record the judging time and check whether
the judge is right or not, the average judging time and
the correct judging rate for the 30 equations will be ana-
lyzed.
3. RESULTS
3.1. Vigilance Reaction Analysis
The vigilance reaction performance under two kinds of
experimental condition in each period was analyzed by
paired-samples T test, in addition, the vigilance reaction
performance under the same experimental condition in
three periods was analyzed with ANOVA, and the result
is shown in Ta b l e 1 . The same analysis to short-term
memory, addition arithmetic, and results are shown in
Ta b l e 2 , Ta b l e 3 , and Ta b l e 4 .
Ta b l e 1 shows that in three experimental periods, the
subjects who took LTN have significantly higher vigi-
lance than those without LTN, such situation especially
obvious at 14:30-15:30, the napping subjects’ rate of
signals responded wrong is 10% lower than that of not
napping ones, even at 16:30-17:30 and 20:00-21:00, the
rate of signals responded wrong is also 4% lower, which
proves that lunch time napping exert positive effect on
vigilance for people no matter in the afternoon or in the
early evening.
Ta b l e 1 also shows that for the LTN subjects, their
vigilance hadn’t changed significantly in the three ex-
perimental periods; however, as for the not having LTN
subjects, their vigilance at 14:30-15:30 is significantly
lower than that at 16:30-17:30 and 20:00-21:00, there
wasn’t significant difference between the second period
and third period.
3.2. Short-term Memory Analysis
Ta b l e 2 lists the comparative analysis results of subjects’
short-term memory capacity under two experimental
conditions and in three experimental periods.
It can be seen from Tab l e 2 that only at 14:30-15:30,
the subjects who took LTN have better short-term mem-
ory performance than those without LTN, at 16:30-17:30
and 20:00-21:00, there wasn’t significant difference be-
tween them.
Ta b l e 2 shows that, as for the subjects who took LTN,
the significant difference about short-term memory ca-
pacity wasn’t found in three periods, however, as for the
subjects who didn’t take LTN, their short-term memory
performance at 14:30-15:30 is worse than that at
16:30-17:30 and 20:00-21:00, and there wasn’t signifi-
cant difference between 16:30-17:30 and 20:00-21:00.
3.3. Addition Arithmetic Analysis
In order to analyze the effect of LTN on human arithme-
tic calculation performance, this research made the
comparative analysis of calculation speed and calcula-
tion accuracy rate under two different experimental con-
ditions and in three experimental periods, the results
shown in Ta b l e 3 and Ta b l e 4 .
Ta b l e 3 lists the comparative analysis results of
arithmetic calculation speed under two experimental
conditions and in three experimental periods.
Ta b l e 3 shows that only at 14:30-15:30, the arithmetic
calculation speed of the subjects who took LTN is sig-
nificantly faster than that of those without LTN, while at
16:30-17:30 and 20:00-21:00, the significant difference
wasn’t found between them.
As can be seen from Tabl e 3 , for the subjects who
took LTN, their arithmetic calculation speed is almost
the same, but for the subjects who didn’t take LTN, the
arithmetic calculation speed at 14:30-15:30 is signifi-
cantly slower than that at 16:30-17:30 and 20:00-21:00,
and there wasn’t significant difference between
16:30-17:30 and 20:00-21:00.
Ta b l e 4 lists the comparative analysis results of the
calculation accuracy rate under two experimental condi-
tions and in three experimental periods.
Ta b l e 4 shows that only at 14:30-15:30, the calcula-
tion accuracy rate of subjects who took LTN is signifi-
cantly higher than that of those without LTN, while at
16:30-17:30 and 20:00-21:00, the significant difference
couldn’t be found between them.
As can be seen from Tab l e 4 , as for the subjects who
took LTN, their arithmetic calculation accuracy rate is
almost the same, but for the subjects who didn’t take LTN,
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287
Ta
b l e 1 . Vigilance reaction (the rate of signal responded wrong).
experimental periods
Experimental
condition
the rate of
signal re-
sponded
wrong
14:30-15:30 16:30-17:30 20:00-21:00
F LSD
Mean
0.054
(NVR1)
0.063
(NVR2)
0.060
(NVR3)
Having lunch
time napping
Std.dev. 0.044 0.043 0.045
0.309
NVR1NVR2
NVR1NVR3
NVR2NVR3
Mean 0.148
(NNVR1)
0.105
(NNVR2)
0.102
(NNVR3)
Not Having
lunch time nap-
ping Std.dev. 0.060 0.055 0.058
5.948
**
NNVR1> NNVR2
NNVR1> NNVR3
NNVR2NNVR3
T 20.828
**
10.779
**
9.069
**
Ta b l e 2 . Short-term memory capacity (the number of letters recalled correctly).
experimental periods
Experimental
condition
Short-term
memory
capacity
14:30-15:30 16:30-17:30 20:00-21:00
F LSD
Mean
8.05
(NSM1)
8.09
(NSM2)
8.01
(NSM3)
Having lunch
time napping
Std.dev. 0.340 0.373 0.412
0.383
NSM1NSM2
NSM1NSM 3
NSM2NSM 3
Mean
7.30
(NNSM1)
7.96
(NNSM2)
7.92
(NNSM3)
Not Having
lunch time nap-
ping Std.dev. 0.390 0.582 0.334
20.588
**
NNSM1< NNSM2
NNSM1< NNSM3
NNSM2NNSM3
T 31.068
**
1.145 1.665
Table 3. Arithmetic calculation speed (seconds/one equation).
experimental periods Experimental
condition
arithmetic
calculation
speed
14:30-15:30 16:30-17:30 20:00-21:00
F LSD
Mean 5.06
(NCS1)
5.03
(NCS2)
4.99
(NCS3)
Having lunch
time napping
Std.dev. 0.339 0.338 0.402
0.322
NCS1NCS2
NCS1NCS3
NCS2NCS3
MeNot Having
lunch time nap-
ping
an 5.49
(NNCS1)
5.01
(NNCS2)
5.04
(NNCS3)
Std.dev. 0.402 0.405 0.337
14.980
**
NNCS1< NNCS2
NNCS1< NNCS3
NNCS2NNCS3
T 15.086
**
0.813 1.708
Ta b l e 4 . The calculation accuracy rate.
experimental periods
Experimental
condition
the calcula-
tion accuracy
rate
14:30-15:30 16:30-17:30 20:00-21:00
F LSD
Mean
0.763
(NCAR1)
0.762
(NCAR2)
0.766
(NCAR3)
Having lunch
time napping
Std.dev. 0.041 0.042 0.040
0.058
NCAR1NCAR2
NCAR1NCAR3
NCAR2NCAR3
Mean
0.701
(NNCAR1)
0.756
(NNCAR2)
0.752
(NNCAR3)
Not Having
lunch time nap-
ping Std.dev. 0.763 0.072 0.075
5.272
**
NNCAR1< NNCAR2
NNCAR1< NNCAR3
NNCAR2NNCAR3
T 7.423
**
0.670 1.391
the arithmetic calculation accuracy rate at 14:30-15:30
is significantly lower than that at 16:30-17:30 and
20:00-21:00, and there wasn’t significant difference be-
tween 16:30-17:30 and 20:00-21:00.
4. DISCUSSION
4.1. Conclusions
This research showed that as for the subjects who didn’t
take LTN, their mental work performance at 14:30-15:30
is significantly worse than that at 16:30-17:30 and
20:00-21:00, while as for those who took LTN, their
mental work performance almost is the same in three
experimental periods, which indicated that midafternoon
nap zone as Hayashi et al. [10], Broughton mentioned
exists objectively for habitual nappers [11], this experi-
ment provided the direct evidence for their standpoint.
This research also showed that the subjects who took
LTN have significantly better mental work performance
than those without LTN at 14:30-15:30, which proved
that LTN could overcome habitual nappers’ “midafter-
noon nap zone”.
It is interesting that as for mental work performance
of such task as short-term memory and arithmetic calcu-
lation, there wasn’t significant difference between the
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subjects who took LTN and those who didn’t take it at
16:30-17:30 and 20:00-21:00, however, as for vigilance
reaction, the subjects who took LTN have significantly
better performance than those who didn’t take it at the
periods as above, which may be caused by the different
nature of the experimental tasks. In specification, the
experimental task of vigilance reaction is relatively bald,
such tasks may easily induce the subjects who didn’t
take LTN to desire sleep, and the result is that their per-
formance is worse than the subjects who took LTN. Ha-
yashi et al. also took for that nap could reduce human
sleepiness and enhance vigilance [7,8,12]. However, as
for short-term memory and arithmetic calculation, these
tasks’ mental workload are relatively overload, the sub-
jects who didn’t take LTN weren’t easily to stimulate
sleepiness, and the result is that their performance are
the same as those who took LTN. Hayashi et al. have
also gotten such conclusion [7]. This research results
indicated that the effect of LTN on habitual nappers’
mental work performance is moderated by the nature of
mental work at 16:30-17:30 and 20:00-21:00.
It is worth noting that this research didn’t deny the
existence of sleep inertia. Hayashi et al. hold that sleep
inertia is inevitable [7], and Taub [13], Dinges et al. be-
lieved that sleep inertia may last 15-35 minutes [14]. In
this study, the measurement of mental work performance
is carried out 30 minutes after LTN, as for the subjects
who took LTN, their mental work performance has not
changed significantly, which provides indirect evidence
for that sleep inertia may last 15-35 minutes, because if
sleep inertial exceeds 30 minutes, the mental work per-
formance of the subjects who took LTN at 14:30-15:30
should be lower than that at 16:30-17:30 and 20:00-21:00,
but this experiment result wasn’t the case.
It should be noted that the above conclusions are got
with the subjects who have LTN habit and took normal
sleep at night and 1 hour and a half naps at noon, if ex-
perimental context was not the case, the conclusion of
this study may be different, many scholars believed that
the effects of naps depend on the duration of prior wake-
fulness, the time of day of the nap, and its duration
[15,16].
Many people feel that they are sleepy and work ineffi-
ciently in the afternoon and evening without LTN; how-
ever as for the complex and over-workload task, such as
short-term memory and arithmetic calculation, the con-
clusion of this study is contradict with it, it doesn’t mat-
ter whether to take LTN or not, human work perform-
ance of such complex task at 16:30-17:30 and 20:00-21:00
is the same, the reason may due to the difference be-
tween experiment and reality. In the experiment, sub-
jects’ attention is highly focused, the pace of task is rela-
tively fast, the experiment duration is short (each period
about 1 hour), and also strong incentive provided. In
reality, the pace of many tasks is slow, and the work du-
ration is long, which easily induce people to be relaxed
and stimulate sleepiness. Despite some difference be-
tween experimental context and reality, we think that
this experiment proved that at least in theory, for com-
plex and over-workload mental work, LTN is a phe-
nomenon to be overcome temporarily in the later after-
noon and in the early evening (16:30-17:30 and
20:00-21:00), not having LTN didn’t exert significant
negative effect to the performance of such task.
4.2. Recommendations
As for habitual nappers, because of LTN can ease such
physical embarrassment as mid-afternoon nap zone,
therefore, LTN is needed if conditions allow, especially
for those whose home is near to their work site. For the
task of vigilance reaction, LTN is particularly important
because LTN can improve its performance in the after-
noon and evening.
Whether having LTN or not has great influence on
habitual nappers’ mental work efficiency at 14:30-15:30
in order to eliminate the negative influence, on one
hand, the government departments should try to avoid
arranging important mental activities at this period of
time, such as examinations, and so on. Unfortunately,
Chinese government departments doesn’t seem to no-
tice it, for example, the most important college en-
trance examination, its examination time in the after-
noon was always from 14:00 to17:00, as for some
students who did not take LTN, their test score are
likely to be lower than their real achievements, which
is unfair for them to compete with students who have
comfort LTN condition. On the other hand, many
Chinese enterprises should adjust their shiftwork
schedule, that is changing the present shiftwork time-
table (8:00-16:00, 16:00-24:00, 24:00 -8:00) into the
new one (6:00-14:00, 14:00-22:00, 22;00-6:00), which
can let habitual nappers avoid not had HLT on duty
yet at 14:30-15:30.
4.3. Limitations and Future Directions
All the subjects participated in this experiment have
LTN habit, although it consists of the Chinese work and
rest mode, we can’t find out the effect of LTN on mental
work efficiency of those who haven’t LTN habit, there is
no doubt that to study it is an interesting work, for ex-
ample, if we find that LTN has no significant effect on
mental work efficiency of those who haven’t LTN habit,
in addition, changing the LTN habit doesn’t bring sig-
nificant bad physical influence, then to reform Chinese
public sectors’ work and rest timetable is go without
saying, because the timetable (9:00 -17:00) in many pri-
vate sector is more reasonable than the timetable (8:00
-12:00 and 14:00-17:30) in public sectors obviously,
which keeps the continuity of eight hours work a day
and not require the public to wait out of the government
G. J. Zhang et al. / HEALTH 1 (2009) 284-289
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office at 12:00-14:00.
[8] Hashi, M., Makiko, W
. and Hori, T. (1999) The effects of
a 20 min nap in the mid-afternoon on mood, performance
and EEG activity. Clini cal Neurophysiology., 110,
272–279.
5. ACKNOWLEDGMENT
[9] Driskell, J.E. an
d Mullen, B. (2005) The efficacy of naps
as a fatigue countermeasure: a meta-analytic integration.
Human Factors., 2, 360-377.
This study was supported by the Science and Technology Research
Project of Hubei province under Grant B20080402, and also was sup-
ported by the Humanity Social Science Foundation of Hubei province
under Grant 2008y054.
[10] Hay
ashi, M., Morikawa, T. and Hori, T. (2002) Cir-
casemidian 12-hour cycle of slow wave sleep under con-
stant darkness. Clinical Neurophysiology., 113,
1505-1516.
REFERENCES
[11] Broughton, R.J.
(1998) SCN controlled circadian arousal
and afternoon “nap zone”. Sleep Resear
ch Online., 1,
166-178.
[1] Liao
, J.Q. (1996) The effects of napping on human per-
formance of vigilance. Ergonomics., 4, 29-32.
[12] Hay
ashi, M., Fukushima, H. and Hori, T. (2003) The
effects of short daytime naps for five consecutive days.
Sleep Research Online., 5, 13–17.
[2] M
acchi, M.M., Boulos, Z., Ranney, T., Simmons, L. and
Campbell, S.S. (2002) Effects of an afternoon nap on
nighttime alertness and performance in long-haul drivers.
Accident Analysis and Prevention., 34, 825-834.
[13] T
aub, J.M. (1979) Effects of habitual variations in nap-
ping on psychomotor performance, memory, and subjec-
tive states. International Journal of Neuroscience., 9,
97-112.
[3] McEvo
y, R.D. and Lack, L.L. (2006) Medical staff work-
ing the night shift: can naps help? Medical Journal of
Australia., 7, 349-350.
[14] Di
nges, D.F., Orne, E.C., Evans, F.J. and Orne, M.T.
(1981) Performance after naps in sleep-conductive and
altering environments. In Johnson, L.C., Tepas, D.I.,
Colquhon, W.P. & Colligan, M.J. (Eds.), Biological
Rhythms, Sleep and Shift Work. S. P. Medical and Scien-
tific Books., New York, 539-552.
[4] Mednick, S.C
., Nakayama, K. and Cantero, J.L., et al.
(2002) The restorative effect of naps on perceptual dete-
rioration. Nature Neuroscience., 7, 676-680.
[5] Backhaus, J. and Junghanns, K. (2006) Daytime naps
improve procedural motor memory. Sleep Medicine.,
7,508–512.
[15] L
umley, M., Roehns, T., Zorick, F., Lamphere, J. and
Roth, T. (1986) the alerting effects of naps in
sleep-deprived subjects. Psychophysiology., 23, 403-408.
[6] Milner
, C.E., Fogel, S.M. and Cote, K.A. (2006) Habitual
napping moderates motor performance improvements
following a short daytime nap. Biological Psychology.,
73, 141–156.
[16] Naitoh, P
. (1981) Circadian cycles and restorative power
of naps. In Johnson, L.C., Tepas, D.I., Colquhon, W.P. &
Colligan, M.J. (Eds.), Biological Rhythms, Sleep and
Shift Work. S. P. Medical and Scientific Books., New
York, 553-580.
[7] Hay
ashi, M., Ito, S. and Hori, T. (1999) The effects of a
20-min nap at noon on sleepiness, performance and EEG
activity. International Journal of Psychophysiology., 32,
173-180.
Openl
y accessible at
... Studies on how an afternoon nap affects alertness and task performance have revealed both positive (Brooks & Lack, 2006;Mantua & Spencer, 2017; and few Zhang et al., 2009) effects. Several factors may explain these contradictory findings, such as manipulation of a nap (i.e., duration or timing) (Milner & Cote, 2009) and different tasks employed. ...
... Several factors may explain these contradictory findings, such as manipulation of a nap (i.e., duration or timing) (Milner & Cote, 2009) and different tasks employed. Studies using various cognitive tasks within one study paradigm evidenced no consistent effects of napping on performance across tasks Zhang et al., 2009). For example, compared with the no-nap condition, an afternoon nap benefited performance on sustained attention and response inhibition but not on conflict monitoring , suggesting that the cognitive domain, which varied in task complexity, might moderate how napping affects task performance. ...
... However, it remains unknown whether and to what extent task type moderates the effects of napping and bright light. Some studies revealed that a short nap enabled better performance on simple tasks than on complex cognitive tasks, and that is because simple tasks are monotonous and thus more sensitive to sleepiness (Tietzel & Lack, 2002;Zhang et al., 2009). On the other hand, a few studies showed that performance on more demanding tasks (e.g., executive function) benefited more from bright light exposure than did performance on simple tasks (e.g., sustained attention) (Huiberts, Smolders, & de Kort, 2015Slama et al., 2015). ...
Article
Previous research revealed inconsistent effects of bright light or a short nap at noon on alertness and performance across different tasks. The current study aimed to explore whether the effects of bright light and a short nap at noon on task performance depended on the cognitive domain. Bright light (1,200 lx, 4,000 K at eye level), nap (near darkness) and control (200 lx, 4,000 K at eye level) conditions were performed from 1:00 to 1:40 PM on three non-consecutive days with a counterbalanced order across participants. After being assigned to one of three conditions, participants underwent two repeated test sessions, each including a psychomotor vigilance task, a go/no-go task, and a paced visual serial addition task, with an interval of more than 1 h, to assess the persistent effects of napping and bright light. Subjective sleepiness, vitality, self-control and mood were also measured. Results showed that accuracy on the go/no-go task and the paced visual serial addition task improved significantly throughout the entire experiment session after napping, whereas reaction speed on the paced visual serial addition task improved time-dependently in the bright light intervention, with a higher reaction speed in only the first test session. Nearly all subjective states benefited from napping but not from bright light. These findings suggested that the effects of bright light and an afternoon nap on task performance would depend on the cognitive domain. An afternoon nap may elicit more effective and persistent benefits on task performance and subjective states.
... In some countries, such as in China, most university students are used to take a short post-lunch nap during working days. Multiple empirical studies have demonstrated that people taking a brief nap (20-40 min) would promote afternoon function including vigilance, sustained attention, executive functions, logic reasoning, memory, and learning performance (5,(7)(8)(9)(10)(11)(12), whereas a lost opportunity of midday nap would lead to various impaired effects on alertness, mood, and performance ability, especially for those who habitually takes a nap (7,(9)(10)(11). ...
... In some countries, such as in China, most university students are used to take a short post-lunch nap during working days. Multiple empirical studies have demonstrated that people taking a brief nap (20-40 min) would promote afternoon function including vigilance, sustained attention, executive functions, logic reasoning, memory, and learning performance (5,(7)(8)(9)(10)(11)(12), whereas a lost opportunity of midday nap would lead to various impaired effects on alertness, mood, and performance ability, especially for those who habitually takes a nap (7,(9)(10)(11). ...
Article
Full-text available
The post-lunch dip in alertness and performance was widely experienced during the early afternoon. Taking a short nap was documented as a practical strategy for habitual nappers to counteract the decline of alertness and performance. Yet, it remains unknown whether bright light exposure in the early afternoon working hours could alleviate the performance deficits caused by a post-lunch nap loss for habitual nappers. Seventeen undergraduate students who had a long-term habit of taking a post-lunch nap were assigned to three interventions: (1) a short nap + normal indoor light (100 lx, 4,000 K at eye level); (2) no nap + normal indoor light, and (3) no nap + blue-enriched bright light (1,000 lx, 6,500 K at eye level), in which subjective alertness (Karolinska Sleepiness Scale, KSS), mood (Positive and Negative Affect Schedule, PANAS), and task performance in sustained attention (psychomotor vigilance test, PVT), response inhibition (go/no-go task), and working memory (paced visual serial addition test, PVSAT) were measured. Results showed that a post-lunch nap deprivation significantly increased subjective sleepiness and negative mood and impaired performance in PVT and PVSAT, while exposure to bright blue-enriched white light vs. normal indoor light in the early afternoon significantly relieved such negative effects on mood, sleepiness, and performance in PVSAT; subjective positive mood and performance in PVT and go/no-go task remained unaffected with light intervention. These findings suggested that bright blue-enriched white light exposure could be a potential strategy for those who are suffering from drowsiness and low working memory following a habitual midday nap loss.
... In contrast to the effects on sustained attention, the current study did not find the beneficial effects of napping on working memory, regardless of the task difficulty. These findings were in accordance with those in two early studies (Takahashi and Arito, 2000;Zhang et al., 2009) but contrasted with other studies reporting improvement in working memory following a midday time nap (Lau et al., 2015;MacDonald et al., 2018;Mulrine et al., 2012). Several factors may explain these inconsistencies, such as duration of napping and night sleep restriction. ...
Article
Taking a short midday nap has been associated with higher alertness and better cognitive task performance. Yet, the mechanisms associated with nap-dependent performance enhancement are unclear. The current study was conducted to explore the impact of physiological arousal during cognitive task and sleep architecture during a pre-task nap on post-nap behavioral outcomes. A within-subjects design (N = 18) was employed, in which participants either took a nap or remained awake for 40 min during the post-lunch period. The psychomotor vigilance test (PVT) and n-back task were administered to assess sustained attention and working memory, respectively, with each task including one block of easy trials and one block of difficult trials. Results showed that a short midday nap improved sustained attention but not working memory. In addition, a midday nap induced lower physiological arousal during the performance on both cognitive tasks, with relatively higher delta and lower beta activity. The relative power of theta and alpha were positively correlated with performance on the easy PVT, whereas the alpha power was negatively correlated with performance on the difficult PVT, and the theta power was negatively correlated with reaction speed in the n-back task regardless of the task difficulty. Meanwhile, the shorter total sleep time and longer time of wake after sleep onset were associated with the faster overall reaction speed in PVT easy trials. These findings suggested that both changes in physiological arousal and sleep variables might account for changes in task performance after a short midday nap.
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Multiple studies have established the efects of afernoon naps on cognition. However, relatively few studies have investigated the domain of executive functions. Moreover, the efects of napping on inhibition are far from conclusive. Te present study employed adult habitual nappers to investigate the efects of afernoon nap deprivation on response-based inhibition assessed by a Go/No-go task and stimulus-based inhibition assessed by a Flanker task and on alertness assessed by a psychomotor vigilance test (PVT) and the Karolinska Sleepiness Scale (KSS). Te results showed that afernoon nap deprivation signifcantly decreased participants’ accuracy and reaction speed for the Go/No-go task but not for the Flanker task. In addition, participants’ alertness was signifcantly impaired afer nap deprivation in terms of increased subjective sleepiness and worse PVT performance. Task-specifc efects of napping on inhibition were demonstrated. The implications of the results are discussed.
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Since the invention of artificial light, people have been working, studying and playing for longer hours than ever before. They are also sleeping less as a result. This article examines the impact of sleep deprivation on people generally, and specifically on college students. Students accrue a large sleep debt that impairs their ability to function adequately. Students suffering from sleep deprivation can be as impaired as if they are drunk. They suffer damage to their minds and bodies. Adequate sleep can repair this damage, but with the many demands on college students, they may be unlikely to be able to accomplish this. Studies have indicated that naps are beneficial in helping to reduce students’ sleep debts. Universities are realizing the importance of naps, and university libraries may be ideal locations for napping stations. Several options of providing students with safe comfortable napping areas are discussed.
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This study examines whether the benefits of a short midday nap on habitual nappers’ mental performance depend on the cognitive domain and the task difficulty. Eighteen healthy college students with the longterm habit of a midday nap (13:00–14:00 hours) participated in a napdeprivation study. On two separate days with at least 3 days in between, participants either took a nap or remained awake, and were subsequently tested on a simple sustained attention task (Psychomotor Vigilance Test), two more complex attention tasks (Go/No-Go and Flanker task) and one working memory task (2-back). For each task, an easy and a difficult version were administered. The time course of subjective sleepiness and mood were also measured in both napping conditions. The results revealed that short midday nap deprivation significantly impaired participants’ performance on both the easy and difficult versions of the Psychomotor Vigilance Test task, as well as accuracy but not reaction speed in the Go/No-Go task. Accuracy in the difficult version of the Flanker task and the 2-back task was also lower in the no-nap condition, while reaction speed in the 2-back task but not the Flanker task was reduced without a nap in both the easy and difficult versions. Moreover, subjective sleepiness was significantly increased after nap deprivation, but moods remained unaffected in the no-nap condition. These findings contribute to current research suggesting that effects of a midday nap on task performance depend on the cognitive domain as well as task difficulty. Our study highlights the importance of considering task characteristics to evaluate the benefits of a regular midday nap in practical working life.
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Beneficial effects of napping or bright light exposure on cognitive performance have been reported in participants exposed to sleep loss. Nonetheless, few studies investigated the effect of these potential countermeasures against the temporary drop in performance observed in mid-afternoon, and even less so on cognitive flexibility, a crucial component of executive functions. This study investigated the impact of either an afternoon nap or bright light exposure on post-prandial alterations in task switching performance in well-rested participants. Twenty-five healthy adults participated in two randomized experimental conditions, either wake versus nap (n=15), or bright light versus placebo (n=10). Participants were tested on a switching task three times (morning, post-lunch and late afternoon sessions). The interventions occurred prior to the post-lunch session. In the nap/wake condition, participants either stayed awake watching a 30-minute documentary or had the opportunity to take a nap for 30 minutes. In the bright light/placebo condition, participants watched a documentary under either bright blue light or dim orange light (placebo) for 30 minutes. The switch cost estimates cognitive flexibility and measures task-switching efficiency. Increased switch cost scores indicate higher difficulties to switch between tasks. In both control conditions (wake or placebo), accuracy switch-cost score increased post lunch. Both interventions (nap or bright light) elicited a decrease in accuracy switch-cost score post lunch, which was associated with diminished fatigue and decreased variability in vigilance. Additionally, there was a trend for a post-lunch benefit of bright light with a decreased latency switch-cost score. In the nap group, improvements in accuracy switch-cost score were associated with more NREM sleep stage N1. Thus, exposure to bright light during the post-lunch dip, a countermeasure easily applicable in daily life, results in similar beneficial effects as a short nap on performance in the cognitive flexibility domain with possible additional benefits on latency switch-cost scores.
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The effect of napping for varying durations after one night of sleep deprivation was examined. Sleep latency tests were used to determine levels of sleepiness/alertness at 2, 4, 6, and 8 hrs following a morning nap of 0, 15, 30, 60, or 120 min duration. Ten normal-sleeping, young adult volunteers spent two consecutive days and the intervening night in the sleep laboratory on each of five weeks. Baseline sleep latencies were recorded the first day, sleep was deprived that night, a nap was taken at 0900 hrs, and sleep latencies were again recorded on the second day. The naps had differential alerting effects related to their duration, but none of the naps returned mean sleep latency for the 8 hrs to its basal levels. Alertness increased with nap duration, reaching its highest level with a 60-min nap; the 120-min nap was no more alerting than the 60-min nap. During the second hour of the 120-min nap, sleep became more fragmented with more shifts to stage 1 sleep or wake. Increased alertness was not strongly related to the sleep stage composition of the naps, the best predictor being minutes of slow wave sleep. Increased alertness was not detected until the second latency test 4 hrs after napping.
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Human performance on visual texture discrimination tasks improves slowly (over days) in the absence of additional training. This 'slow learning' requires nocturnal sleep after training and is limited to the region of visual space in which training occurred. Here, we tested human subjects four times in one day and found that with repeated, within-day testing, perceptual thresholds actually increased progressively across the four test sessions. This performance deterioration was prevented either by shifting the target stimuli to an untrained region of visual space or by having the subjects take a mid-day nap between the second and third sessions.
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Effects of habitual variations in napping on psychomotor performance, short-term memory and subjective states were investigated. The subjects were 32 healthy male university students who napped twice or more weekly in themorning and at night. Sixteen were randomly assigned to a control group and 16 to a nap(treatment) group. The experiment comprised two conditions of electrographically (EEG) recorded sleep for the nap group and two EEG monitored conditions of wakefulness for the controls. These conditions were scheduled from 9:35 to 11:35 a.m. and 12 hr later between 9:35 p.m. and 11:35 p.m. Measurements were obtained from: (a) a continuous 10-min auditory reaction time task, (b) a free recall task of short-term memory, (c) an activation-mood adjective check list, and (d) the Stanford Sleepiness scale. Except for memory the dependent variables of waking function were assessed 20 min before and 20 min after all conditions. Following each sleep condition the nap group as opposed to the controls showed a statistically significant improvement in reaction time performance, higher short-term retention, less reported sleepiness and elevated subjective states reflected by fice factors on the adjective mood-activation check list. Among the correlations computed the largest significant coefficients were of stage 4 and REM with posttreatment Stanford Sleepiness ratings. After naps, increased postdormital sleepiness was correlated with stage 4 and decreased sleepiness with REM sleep. Although few strikingly divergent functional effects were associated with morning and nocturanal naps, these did covary with sleep psychophysiology. It is postulated that the phase, the EEG-sleep stages and possibly the duration of accustomed naps are less salient factors influencing performance when the time since awakening until behavioral assessment can be kept constant.
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The prophylactic effects of a 20-min nap at noon on afternoon sleepiness were studied. Ten young adults who had normal sleep-wake habits without habitual daytime napping were subjected to nap and no-nap conditions at an interval of 1 week. After a nocturnal sleep recording (00.00-08.00 h), their EEG recordings during relaxed wakefulness, mood, performance, and self-ratings of performance level were measured every 20 min from 10.00 h to 18.00 h. For the nap condition, they went to bed at 12.20 h and were awakened when 20 min had elapsed from the onset of sleep stage 1. For the no-nap condition, they rested without sleeping by sitting on a semi-reclining chair. The nap did not improve task performance, however, it improved volition and the self-rating of task performance. It also suppressed subjective sleepiness and attenuated eyes-opened EEG alpha activities. The results suggest that a 20-min nap at noon had partial positive effects on the maintenance of the daytime arousal level.
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This paper outlines a conceptual model for the regulation of the circasemidian sleep propensity process with emphasis on a possible mechanism of the afternoon "nap zone". It is proposed that the afternoon nap zone is due to increasing sleep propensity after morning wakening (Borb ly's Process-S) being overwhelmed by a light-sensitive SCN-dependent circadian arousal process of the type discovered by Edgar et al., (1993) and currently being identified in its pathways and neurochemistry by Jouvet and colleagues. It is maintained that this arousal process is reflected in the circadian core body temperature pattern, and that under normal entrained conditions the latter does not resemble a sine-wave or skewed sine-wave. Rather it is very asymmetrical in time and somewhat asymmetrical in amplitude. Cosinor type analyses which enforce symmetry in time and amplitude are therefore ill suited to adequately curve-fit the empirical data. The shape of the circadian arousal system was clarified by meta-analyses of data from three laboratories for three conditions: the normal entrained state, the constant routine, and temporal isolation. Under normal entrained conditions for about one-third of the circadian day core body temperature, and therefore the assumed intensity of the circadian arousal system, is below the mesor with the nadir being at about 0500h; and for about two-thirds of the circadian day it is above the mesor with the acrophase on average being at about 2100h. For modeling purposes, the homeostatic process (Process-S) employed the actual data of the Zurich laboratories for night sleep, but altered the equation for the daytime period to ensure an exponential increase after wake-up. Combining these modified processes indicated that the nap zone could be explained, as predicted, by an increasing homeostatic pressure for sleep across the daytime being reversed by the circadian arousal process. This 2-process combination predicted quite well the shape of the entire circasemidian sleep/wake propensity process and can explain the presence of morning sleep inertia without requiring a third process. It would appear that the circadian arousal process can be modified in phase and in amplitude by a number of normal and pathological conditions.
Article
The effects of an afternoon nap on alertness and psychomotor performance were assessed during a simulated night shift. After a night of partial sleep restriction, eight professional long-haul drivers either slept (nap condition) or engaged in sedentary activities (no-nap condition) from 14:00 to 17:00 h. Alertness and performance testing sessions were conducted at 12:00 (pre-nap baseline), 24:00, 02:30, 05:00 and 07:30 h, and followed 2-h runs in a driving simulator. In the nap condition, the subjects showed lower subjective sleepiness and fatigue, as measured by visual analog scales, and faster reaction times and less variability on psychomotor performance tasks. Electrophysiological indices of arousal during the driving runs also reflected the beneficial effects of the afternoon nap, with lower spectral activity in the theta (4-7.75 Hz), alpha (8-11.75 Hz) and fast theta-slow alpha (6-9.75 Hz) frequency bands of the electroencephalogram, indicating higher arousal levels. Thus, a 3-h napping opportunity ending at 17:00 h improved significantly several indices of alertness and performance measured 7-14 h later.
Article
The effect of napping on motor performance was examined in habitual and non-habitual nappers who were randomly assigned to a nap or reading condition. Motor procedural learning and auditory discrimination tasks were administered pre- and post-condition. Both groups reported improved alertness post-nap, but not post-reading. Non-habitual nappers fell asleep faster and tended to have greater sleep efficiency, but did not differ from habitual nappers on other sleep architecture variables. Habitual nappers had greater alpha and theta EEG power in stage 1, and greater delta, alpha and sigma power in stage 2 sleep. Motor performance deteriorated for non-habitual nappers who napped, but improved for all others. The number of sleep spindles and sigma power (13.5-15 Hz) significantly predicted motor performance following the nap, for habitual nappers only. Results indicate that motor learning was consolidated in a brief nap and was associated with stage 2 spindles, but only for those who habitually take naps.
Article
To investigate the impact of a short daytime nap on procedural and declarative memory consolidation. Following a normal night's sleep, 34 young healthy subjects were randomly assigned to a nap or wake condition of about 45min in the early afternoon after learning procedural and declarative memory tasks. Subjects were controlled for alertness and cortisol secretion. The afternoon naps were dominated by sleep stage 2 but contained some slow wave sleep (SWS) and rapid eye movement (REM) sleep as well. Naps significantly improved procedural, but not declarative, memory. Females showed more improvement than males in the declarative memory tasks irrespective of nap or wake. There was no difference between groups with respect to cortisol secretion or alertness. A short nap is favorable for consolidation of procedural memory. The possibly confounding effect of gender should always be considered in research on sleep and memory.
Medical staff working the night shift: can naps help? Performance after naps in sleep-conductive and altering environments
  • R D Mcevoy
  • L L Lack
  • D F Dinges
  • E C Orne
  • F J Evans
  • M T Orne
McEvoy, R.D. and Lack, L.L. (2006) Medical staff working the night shift: can naps help? Medical Journal of Australia., 7, 349-350. [14] Dinges, D.F., Orne, E.C., Evans, F.J. and Orne, M.T. (1981) Performance after naps in sleep-conductive and altering environments. In Johnson, L.C., Tepas, D.I., Colquhon, W.P. & Colligan, M.J. (Eds.), Biological Rhythms, Sleep and Shift Work. S. P. Medical and Scientific Books., New York, 539-552.