The Effects of Drinking Water on Attention

Abstract

Various studies have shown that dehydration can lead to decrease of attention, concentration and other cognitive and motor functions, as well as the feeling of fatigue and headache. The main purpose of this study was to test if drinking water affects the student results on the Attention Test. The experiment included 91 first-year students of University for Applied Sciences VERN’. In the experimental situation participants could drink as much water as they wanted during the class, and the minimum was a few sips. In the control situation, participants did not drink water and were not allowed do so during the break. Experiments were conducted during regular classes, in two five-minute blocks, with a two minute break in between. Results did not confirm the impact of drinking water on the overall performance on the Attention Test. However, a slight but statistically significant increase in the average results was found in the experimental situation in the second five-minute measurement session.

Full text

Procedia - Social and Behavioral Sciences 159 ( 2014 ) 577 – 583
Available online at www.sciencedirect.com
ScienceDirect
1877-0428 © 2014 Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license
(http://creativecommons.org/licenses/by-nc-nd/3.0/).
Peer-review under responsibility of the Academic World Education and Research Center.
doi: 10.1016/j.sbspro.2014.12.428
WCPCG 2014
The Effects of Drinking Water on Attention
Irena Miljkovic Krecara
*
, Maja Kolegaa, Silvana Fratric Kunaca
aUniversity of Applied Sciences VERN', Trg bana Jelacica 3, 10000 Zagreb, Croatia
Abstract
Various studies have shown that dehydration can lead to decrease of attention, concentration and other cognitive and motor
functions, as well as the feeling of fatigue and headache. The main purpose of this study was to test if drinking water affects the
student results on the Attention Test. The experiment included 91 first-year students of University for Applied Sciences VERN’.
In the experimental situation participants could drink as much water as they wanted during the class, and the minimum was a few
sips. In the control situation, participants did not drink water and were not allowed do so during the break. Experiments were
conducted during regular classes, in two five-minute blocks, with a two minute break in between. Results did not confirm the
impact of drinking water on the overall performance on the Attention Test. However, a slight but statistically significant increase
in the average results was found in the experimental situation in the second five-minute measurement session.
© 2014 The Authors. Published by Elsevier Ltd.
Peer-review under responsibility of the Academic World Education and Research Center.
Keywords: attention; cognitive performance; drinking water; hydration;
1. Introduction
The human body consists of about 70% of water. The water in the body has numerous physiological roles: it is
essential for the breathing (oxygen transport to the cells) and metabolism, digestion (absorption of nutrients),
detoxification of the body, regulation of the body temperature, maintenance of equal osmotic pressure in cells and
extracellular space etc. (Roganovic, 2011). In short, water provides a number of physical and chemical processes
that are essential to the life of humans, animals and plants. It is common knowledge that it is possible to survive for
a month without food, but we can't survive without water for even one week. Loss of large amounts of water and
*
Irena Miljkovic Krecar. Tel.: +385 91 4825 841
E-mail address: irena.miljkovic@vern.hr
© 2014 Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license
(http://creativecommons.org/licenses/by-nc-nd/3.0/).
Peer-review under responsibility of the Academic World Education and Research Center.

578 Irena Miljkovic Krecar et al. / Procedia - Social and Behavioral Sciences 159 ( 2014 ) 577 – 583
electrolytes leads to dehydration. Dehydration is a condition that occurs when the loss of body fluids exceeds the
amount that is taken in and this disrupts the delicate balance of minerals in body fluids. The degree of dehydration is
determined depending on the percentage of lost body fluids. Mild dehydration occurs when the body loses about 1-
2% of total body fluids, and severe dehydration is considered to take place when the body loses more than 5% of the
total fluids (Szinnai et al., 2004). A definite sign of dehydration is thirst, but thirst occurs only when the person has
already lost 0.8 - 2% of total fluids, i.e. when they are already slightly dehydrated. The symptoms of mild
dehydration include headache, confusion, fatigue, reduced alertness, and reduced ability to concentrate (Kleiner,
1999). Dehydration negatively affects physical performance, as evidenced by a number of studies conducted on
soldiers and manual workers (Pitts et al., 1994). Exploring the impact of dehydration on cognitive functions is a
relatively new area of research. However, different cognitive functions are tested in terms of greater or milder
dehydration caused by excessive physical labor, heat and lack of fluid intake, among the respondents of different
age, gender and background. Generally, the results confirm that loss of more than 2% of body fluids (either due to
heat, physical exertion or no water intake) decrease cognitive, visual, psycho-motor and physical performance. For
example, Cian et al. (2001) investigated the effect of dehydration resulting from exercise and heat on memory and
visual-motor activities. Both causes of dehydration proved its adverse impact on memory and perceptual
discrimination. Ritz and Berrut (2005) found that dehydration significantly reduces attention, concentration, short
term memory, and increases response time as well as the feeling of tiredness and headache. Petri et al. (2006)
confirmed the reduction of mental and psychomotor functions in adult, healthy individuals after voluntary 24-hour
dehydration. In children, dehydration is connected with irritability, lethargy and decline of cognitive performance
(D’Anci et al., 2006, Bar-David et al., 2005). Research on young soldiers (Gopinatham et al., 1988) has confirmed
that a mild level of dehydration could be critical, because it reduced the efficiency in solving arithmetic tasks and
had an adverse effect on short term memory and visual-motor tracking. Szinnai et al. (2004) found no decline in
cognitive and motor functioning in young and healthy people due to dehydration, but confirmed the occurrence of
increased fatigue and reduced attention. The authors suggest that in young people compensatory cognitive
mechanisms might emerge leading to increased effort investment. Similar studies conducted in twenty- year- olds
(Armstrong et al., 2012, Ganio et al., 2011), have found gender differences in the effects of mild dehydration (about
1,5%) on cognitive functioning. The decline in cognitive performance in women was lesser than in men but women
had greater mood swings and symptoms such as fatigue, headaches, concentration difficulties etc..In other words,
under the condition of mild dehydration, women show greater emotional sensitivity. Analyzing the results of
previous research studies in this area, Secher and Ritz (2012) confirm the existence of a clear link between
dehydration and reduced cognitive performance. On the other hand, the following question may be raised: could
water intake improve cognitive functions? According to Rogers et al. (2001) it seems that it could. Their results
confirm that drinking water enhances cognitive functions in thirsty subjects. On a sample of school children, Benton
and Burgess (2009) found that drinking water during class is beneficial to their memory, but not to their attention. In
a study conducted by Edmons and Burford (2009) it has been established that children who drink water during class
achieve better results on the visual attention test. Data for adults are not strong enough; previous studies were
methodologically very heterogeneous, which does not allow their generalization (Secher and Ritz, 2012). While
everyone agrees on the importance of regular intake of water, there is no consensus about how much fluid a day is
necessary for optimal functioning of the body (Ritz and Berrut, 2005). According to some indicators, adult men
should drink at least 2,900 ml per day and adult women 2,200 ml per day, if not exposed to heat of physical exertion
(Kleiner, 1999). It is estimated that most people do not care enough about regular intake of fluids and thus live in a
state of mild dehydration. Even in sports, where regular hydration of body is essential, coaches do not have enough
knowledge about hydration; they do not know how much damage dehydration could cause during training or
competition, and about two thirds of the surveyed coaches did not know that alcoholic beverages are a bad
rehydration choice for athletes (Zirdum et al., 2009). School children run an increased risk of dehydration due to
physical activity, sweating and eating salty foods and drinking carbonated beverages. Likewise, students are
exposed to higher risk due to coffee consumption and cigarette smoking. Because of their other responsibilities and
priorities, both groups may ignore regular intake of fluids in the body. In our country there is no systematic research
on the effects of drinking water on cognitive functioning. The main objective of this paper is to collect some
preliminary results that can provide the basis for further research in this area.

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2. Methodology
2.1. Goal
With this experiment we tested whether hydration could improve scores on Attention test. We propose following
null-hypothesis: H1 - There aren't any significant differences in Attention test scores in control situation (without
hydration) as opposed to experimental situation (with hydration).
2.2. Sample, Instrument and Procedure
The study included 91 first-year students of VERN’ University for Applied Sciences, equal ages and both sexes.
The experiment was conducted at two measurement points – in October and December 2012. as a part of regular,
obligatory psychology classes, during last 15 minutes of a 1,5 hours block. At first measurement (in October) one
half of participants (N=44, Group 1) were in control situation, and the other half were in experimental situation
(N=47, Group 2). All participants (at both situations and both measurement points) solved Attention test (AT). This
test is a modification of an old Pieron-Tolouse test, made by psychologist Tomislav Djuric (1985). This test is
intended for measurement of visual attention, and was often applied in professional selection and counseling
situations. It consists of series of small squared characters that distinguish between themselves by position of one
small line. Participants need to count and write down the exact number of inflicted characters, as fast as they can.
While doing that, no help of hand or pencil is allowed, that is, characters should be traced only visually. After
general instruction, several exercise tasks were collectively solved. Then participants solved test for another 5
minutes on their own. Then a short break was made (app. 2 minutes), after which another block of 5-minute testing
was made. This time, different character was traced. Procedure was the same for experimental and control situation
groups, with the only difference being the fact that during the 2-minute break and before first 5-minute testing,
participants in experimental group drank water. Each participant was given one (or more if they asked) 0,5 liter
bottle of natural water, and were allowed to drink as much as they like, with few sips being a minimum. The exact
amount of drank water had to be written down on their tests. In control situation participants weren't allowed to
drink water during or before the testing, that is during the 90 min. of psychology classes. At second measuring (2
months later) same participants solved the same test, but now control group participants were in experimental
situation, and experimental group participants were in control situation.
3. Results
The most important question of this experiment was – do results on Attention test obtained in control situation
differ significantly from results obtained in experimental situation (regardless of measurement point). In Table 1
there are given descriptives for four measuring: two 5-minute measuring in control situation regardless of
measurement point (Control 1 and Control 2) and two 5-minute measuring in experimental situation (Experiment 1
and Experiment 2) regardless of measurement point. Also in table 1, there are given total results for control
(TotalControl 12) and experimental situation (TotalExperiment 12) regardless of measurement point. In control
situation total average result is 44,64 points and in experimental situation average is 45,33 points. T-test statistics
shows that this difference is not statistically significant (table 2).
Table 1. Descriptives for two 5-minute measuring in control situation (Control 1, Control 2), two 5-minute measuring
in experimental situation (Experiment 1, Experiment 2), and total results in control (TotalControl 12) and
experimental situation (TotalExperiment 12) for all participants
Results
N
Min
Max
Mean
Std. Dev
Control 1
91
10
38
22,44
6,93
Control 2
91
6
37
22,20
5,88

580 Irena Miljkovic Krecar et al. / Procedia - Social and Behavioral Sciences 159 ( 2014 ) 577 – 583
TotalControl 12
91
19
69
44,64
11,07
Experiment 1
91
9
38
21,88
6,29
Experiment 2
91
7
36
23,45
6,24
TotalExperiment 12
91
17
73
45,33
10,42
Table 2. T-test for all pairs of results for all participants (N=91)
Compared results
Mean
Std. Dev
Std.Err
Mean
t-test
df
p
Control 1 – Control 2
0,24
6,53
0,69
0,35
90
0,73
Experiment 1 – Experiment 2
-1,57
6,97
0,73
-2,15
90
0,03
TotalCont 12 – TotalExp 12
-0,69
11,98
1,26
-0,55
90
0,58
Control 1 – Experiment 1
0,56
7,48
0,78
0,72
90
0,48
Control 2 – Experiment 2
-1,25
7,20
0,76
-1,66
90
0,10
Control 1 – Experiment 2
-1,01
8,91
0,93
-1,08
90
0,28
Control 2 – Experiment 1
0,32
6,88
0,72
0,44
90
0,66
In table 2 differences between every other pair of results are shown. The only difference that proved to be
statistically significant is the one between two 5-minute measuring in experimental situation. That is, in situation
when they drink water, in first 5-minute block participants score 21,88 points at average, and after two minute break
(during which they also drink water, at second 5-minute measuring) their results increase for 2 points (that is on
23,45). This increasing is statistically significant (p<0,05). We also tested whether differences in average scores
exist when we take into account if participants were in control situation at first measurement point (Group 1) or if
they were in experimental situation at first measuring (Group 2). In table 3 large differences can be seen between
two groups. Group 1 at second measurement point (when they were in experimental situation) scores 10 points
more, than at first measurement point. Group 2 has at second measurement point (when they were in control
situation) 8 points more, then at first measurement point. All these differences are statistically significant (table 4).
That is, results of second measurement point were always significantly higher than results of first measurement
point, regardless of situation (control or experimental). It means that there has been exercise effect on Attention test,
and this effect surpasses potential effect that hydration could have on results.
Table 3. Average results of different measuring separately for participants that were in control or experimental situation at
first measurement point (Group1 or Group2)
Results
Group
N
Mean
Std. Deviation
Std. Error
Mean
TotalControl 12
1
44
39,61
9,26
1,39
2
47
49,34
10,63
1,55
TotalExperiment 12
1
44
49,11
10,11
1,52
2
47
41,79
9,49
1,38
Control1
1
44
19,48
5,23
,79
2
47
25,21
7,23
1,05
Control2
1
44
20,14
5,5
,83
2
47
24,13
5,61
,82
Experiment1
1
44
23,39
5,92
,89
2
47
20,47
6,36
,93
Experiment2
1
44
25,73
5,95
,89
2
47
21,32
5,78
,84

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Table 4. T-test results for Attention test score differences between Group 1 and Group 2
Situation
t-test
df
p
Mean diff
Std. Error Diff
TotalControl 12
-4,64
89
0,00
-9,73
2,1
TotalExp 12
3,57
89
0,00
7,33
2,06
Control 1
-4,31
89
0,00
-5,74
1,3
Control 2
-3,42
89
0,00
-3,4
1,17
Experiment 1
2,26
89
0,02
2,92
1,29
Experiment 2
3,58
89
0,00
4,41
1,23
Finally, as our participants in experimental situation had the liberty to choose the amount of drank water, we tested
if there is a significant correlation between drank water and Attention test results. It is visible in table 5 that none of
correlations with drank water is significant.
Table 5. Correlation matrix for variables – amount of drank water and results on Attention test (first 5-minute
measuring=Experiment1; second 5-minute measuring=Experiment2, and total results=TotalExperiment 12)
Variable
Water
Experiment 1
Experiment 2
TotalExp 12
Water
1
0,00
-0,12
-0,07
Experiment 1
0,00
1
0,38**
0,83**
Experiment 2
-0,12
0,38**
1
0,83**
TotalExp 12
-,007
0,83**
0,83**
1
4. Discussion
The results of the experiment have not confirmed positive effects of hydration on overall results on the Attention
Test. Even though the overall result in the experimental situation (with hydration) is somewhat better, there is no
statistically significant difference compared to the result obtained in the controlled situation (with no hydration). The
only statistically significant difference when comparing all result pairs has been confirmed in the experimental
situation, where the result is significantly increasing (by two points) in the second testing session compared to the
first, i.e. after a short break during which subjects drink water. This means that water may to a smaller extent boost
attention during a mental activity. However, these effects are not instantaneous, but cumulative and are visible only
after an activity has continued for some time. Also, these effects can be explained by a variety of factors – the very
change of activity, the placebo (participants’ belief that the water will boost their attention) or the physiological
effect of water. Interesting results have been obtained in the test analysis depending on whether the students were in
the control or experimental group in the first measurement session. Participants who first acted as the control group
(Group 1) scored as many as 10 points more in the second measurement session, when they were in the experimental
group and drank water. This is a statistically significant difference. However, the difference is significant in the
second group (Group 2) as well, where the subjects were first exposed to the experimental situation and only then to
the control situation. In the second measurement session (no water) they scored 8 points more. In other words, the
results of the second measurement (2 months after the first) have been significantly better in both situations than the
results of the first measurement regardless of whether the students were in the experimental or control situation. A

582 Irena Miljkovic Krecar et al. / Procedia - Social and Behavioral Sciences 159 ( 2014 ) 577 – 583
significantly better performance of all participants in the second measurement session suggests that practice has had
a huge effect on the Attention Test results. The impact of practice, i.e. prior testing experience of this measurement
instrument has by far exceeded the positive effect of hydration on performance. The reliability coefficient of the
Attention Test in the task of detecting one sign proved to be relatively low (r=0.5) in an earlier study as well (Djuric
et al. 1985), where it was established by the retesting method on a sample of high school students (testing was
repeated after 37 days). Participants in this measurement also achieved significantly better results (10 points more
on average) in the second measurement session. This has been explained by the following: the fact that the
participants learned the task in the first measurement session, that they were trained, that they were familiar with
the contents, that their level of concentration and interest increased and that they put more effort in the second
testing. We believe that similar processes had an impact on the results of this experiment, i.e. that the subjects
adopted appropriate task-solving strategies in the first measurement session, which had a positive effect on their
performance in the second measurement session. For future studies on the effect of hydration on visual attention we,
therefore, recommend using another measurement instrument, which is not affected by practice to such a large
extent, so that the possible effect of water on attention could be fully seen. Apart from this, we suggest that the
period of time between to testing sessions should be longer than two months in order to reduce the effect of practice.
Also, as significant effects of hydration were achieved in the second part of the test (the second five-minute period
of work), we recommend administering longer tests, which will be more demanding in terms of using cognitive
skills. We expect that the effects of hydration would have been more evident had the participants experienced more
fatigue due to testing. Two five-minute tests of visual attention are obviously too short to tire out the participants to
the degree where the water would have a positive effect. We assume that there is an optimal level of fatigue where
the water affects cognitive functions the most. Water is likely to help at mild and medium-range tiredness, but has
no effect (or a lesser effect) at a very low or very high level of fatigue. Furthermore, we suggest investigating the
effects of hydration on more complex tasks, too. These tasks may require simultaneous use of various abilities, for
example, decision making skills, good vision, ingenuity, good memory, precision, patience and ‘good nerves’. In
such studies participants report attention related problems, i.e. the need to make an extra psychological effort, which
is not equally easy for all the participants (Djuric et al., 1985). Also, in further studies researchers could use
measuring instruments which, apart from the number of correctly detected signs (as in this measurement) also
evaluate the number of undetected or misdetected signs. In our research, the quantity of consumed water did not
prove to be a significant correlate of the Attention Test results, which may partly stem from the fact that the subjects
were free to choose the quantity of water to drink, and, more importantly, due to different levels of their prior level
of dehydration. As the water tanks and toilettes are easily available on the premises of VERN’ and since we were
unable to make sure that the students did not drink water for only about 70 minutes before the testing (the duration
of classes prior to the experiment), we may assume that their level of dehydration was not sufficiently high to lead to
a significant drop in their concentration. Even though some other studies researched the effect of a higher level of
dehydration (a minimum of 1% of body weight loss) on cognitive functions, in academic contexts such studies are
ethically questionable. Our subjects did not volunteer to participate in the experiment nor did we have evidence of
their general health condition in order to be able to deliberately cause dehydration. Also, possible effects of covert
influence of the researcher on the participants in the study (observer effect) should not be ignored. The procedures
used in the experiment, i.e. the instructions to drink water before and between the two testing sessions could have,
indeed, hinted at the purpose of the study, which may have affected the results. Finally, even though there is a
substantial body of research on the negative effects of dehydration and fatigue on cognitive functions, there is a lack
of research on positive effects of hydration on these functions. In other words, in most studies subjects with different
levels of thirst are subjected to a variety of mental and physical tasks. However, we do not know enough about the
recovery of these functions, i.e. how exactly and at what dynamics water improves these functions following
dehydration and tiredness. We may assume that the relationship between the decline in cognitive functions due to
dehydration and their recovery due to hydration is not linear, which creates the need for further research in this area.
Studies like this are particularly relevant in an academic context as schoolchildren and students tend to forget the
importance of timely (and preventive) intake of water while they are using body fluid reserves, either through
physical activity or by consuming unhealthy food and drinks.

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5. Conclusion
Previous studies have confirmed positive effects of hydration on attention and other cognitive functions in a
situation of dehydration or exhaustion. In our study, no statistically significant difference has been found in the
results achieved by the participants in the experimental situation (with hydration) compared to the control situation
(without hydration). This can be explained by the short duration of the test, i.e. we can assume that the subjects did
not experience any fatigue or dehydration, to which consumed water could have positive effects. Also, since all
respondents (regardless of whether they were in the control or experimental situation) at the second measurement
had significantly higher scores than the first, we assume that the used Attention test shows a strong effect of
exercise, which calls into question its application. In our study, however, there is a small but significant effect of the
break, which includes hydration (and probably earlier consumed water) on the results. Is it a consequence of the
changes in activity, placebo effect or physiological role of water in the body remains an open question. For future
researches we recommend the use of longer and/or more demanding Attention tests (or tests of other cognitive
functions), and better control of the previous stage of participants (de)hydration.
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