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Ergonomics
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The impact of light and colour on
psychological mood: a cross-cultural
study of indoor work environments
Rikard Küller a , Seifeddin Ballal b , Thorbjörn Laike a , Byron
Mikellides c & Graciela Tonello d
a Department of Environmental Psychology , School of
Architecture, Lund Institute of Technology , Box 118, SE-221 00,
Lund, Sweden
b Department of Family and Community Medicine , College of
Medicine, King Faisal University , Box 2114, Dammam, 31451,
Saudi Arabia
c Architectural Psychology Laboratory , School of the Built
Environment, Oxford Brookes University , Oxford, OX3 OBP, UK
d Departamento de Luminotecnia Luz y Vision , Universidad
Nacional de Tucumán , 4000, Tucumán, Argentina
Published online: 20 Feb 2007.
To cite this article: Rikard Küller , Seifeddin Ballal , Thorbjörn Laike , Byron Mikellides & Graciela
Tonello (2006) The impact of light and colour on psychological mood: a cross-cultural study of
indoor work environments, Ergonomics, 49:14, 1496-1507, DOI: 10.1080/00140130600858142
To link to this article: http://dx.doi.org/10.1080/00140130600858142
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The impact of light and colour on
psychological mood: a cross-cultural study
of indoor work environments
RIKARD KU
¨LLER{, SEIFEDDIN BALLAL{, THORBJO
¨RN LAIKE*{,
BYRON MIKELLIDESxand GRACIELA TONELLO{
{Department of Environmental Psychology, School of Architecture,
Lund Institute of Technology, Box 118, SE-221 00 Lund, Sweden
{Department of Family and Community Medicine, College of Medicine,
King Faisal University, Box 2114, Dammam 31451, Saudi Arabia
xArchitectural Psychology Laboratory, School of the Built Environment,
Oxford Brookes University, Oxford OX3 OBP, UK
{Departamento de Luminotecnia Luz y Vision, Universidad Nacional de Tucuma
´n,
4000 Tucuma
´n, Argentina
The aim of the study was to determine whether indoor lighting and colour
would have any systematic impact on the mood of people working indoors.
Earlier studies have mostly focused either on light, colour or windows in
laboratory settings. The present study was carried out in real work
environments at different seasons and in countries with different latitudes.
A total of 988 persons completed all parts of the study. In the countries
situated far north of the equator there was a significant variation in
psychological mood over the year that did not occur in the countries closer to
the equator. When all four countries were considered together, it became
evident that the light and colour of the workplace itself also had an influence
on the mood of persons working there. The workers’ mood was at its lowest
when the lighting was experienced as much too dark. The mood then
improved and reached its highest level when the lighting was experienced as
just right, but when it became too bright the mood declined again. On the
other hand, the illuminance as measured in objective terms, showed no
significant impact on mood at any time of the year. The relationship between
mood and the distance to the nearest window was bimodal. The results also
indicate that the use of good colour design might contribute to a more
positive mood. It is suggested that in future research light and colour should
be studied as parts of the more complex system making up a healthy building.
Keywords: Artificial lighting; Daylight; Interior colour; Psychological mood;
Windows; Work environments
*Corresponding author. Email: thorbjorn.laike@mpe.lth.se
Ergonomics
Vol. 49, No. 14, 15 November 2006, 1496–1507
Ergonomics
ISSN 0014-0139 print/ISSN 1366-5847 online ª2006 Taylor & Francis
http://www.tandf.co.uk/journals
DOI: 10.1080/00140130600858142
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1. Introduction
The effects of light acting via both retinal and extra-retinal routes indicate the great variety
and complexity of its impact beyond the phenomena of vision, including, on one hand,
effects on mood and behaviour and, on the other, physiological effects on autonomic
arousal and hormones (for reviews, see Stone 1999, Ku
¨ller and Ku
¨ller 2001, Veitch et al.
2004). The main aim of the present study was to determine whether indoor lighting and
colour would have any systematic impact on the mood of people working indoors.
Differences in the indoor lighting environment (levels, spectral distribution, temporal
patterns, etc.) do seem to affect people in various ways. Daurat et al. (1993) found that
subjects reported a more positive mood under 2000 than under 300 lux. Belcher and
Kluczny (1987) proposed a model in which mood, visual performance and decision-
making strategy are affected by the visual environment and compete for mental
processing capacity. The mood shift for women was strongly negative for ‘bright’
conditions and near zero for ‘dim’ conditions, whereas men tended to respond in the
opposite direction. Knez and Kers (2000) found that age and gender interacted with the
illuminance and the colour temperature of the lighting, causing different kinds of mood
shifts. McCloughan et al. (1999) showed the existence of systematic influences on mood
from lighting parameters within the range encountered in everyday interior conditions.
On the other hand, studies of the impact of full-spectrum lighting on mood have given
controversial results (Boray et al. 1989, Baron et al. 1992, Ku
¨ller and Wetterberg 1993,
Rusak et al. 1996, Veitch and McColl 2001).
There is some evidence that the colours of an interior space might influence the
psychological mood of individuals in that space (Ku
¨ller and Mikellides 1993). Lightness,
hue and saturation might be of importance, as might the combination and distribution of
the colours in the interior space. A number of studies have compared the impact of
‘warm’ and ‘cool’ colours (e.g. reds and blues) (Stone 2001, 2003). Letting his participants
work in either a red or a blue office space, Janssens (2000) found an interaction between
psychological mood on one hand and performance on the other. Comparing nine
monochromatic office colours, Kwallek et al. (1996) found that saturation was a salient
predictor of differences in mood between males and females.
One outstanding relationship between daylight and mood is the prevalence of seasonal
affective disorder (SAD) in countries far from the equator during the dark season.
Amongst the well-known symptoms of SAD are reduced activity, social withdrawal and
changes in mood, such as increased sadness (Ku
¨ller 2002). The results of several
epidemiological studies indicate the existence of seasonal variations in psychological
mood, the respondents generally ‘feeling worst’ during autumn and winter (Kasper et al.
1989, Harris and Dawson Hughes 1993, Eagles et al. 1997). Thus, depending on the
latitude, season, weather conditions and distance to windows, the occupants might
respond differently to indoor lighting. Furthermore, most studies show that people prefer
to work in environments with windows and that lack of windows and a view to the outside
may have a negative impact on well-being and performance (Ku
¨ller and Wetterberg 1996).
There are, however, very few studies of the impact of windows on psychological mood and
the little there is has been inconclusive (Tennessen and Cimprich 1995, Stone 2003).
2. Problem
Most of the studies cited above have focused on light, colour or windows in laboratory
settings. Even if some of these studies involved highly elaborate experimental designs and
The impact of light and colour on psychological mood 1497
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measurements, it was felt appropriate to consider all these visual factors simultaneously
under realistic working conditions and over a prolonged period of time. In order to
ensure the validity of the outcome, the study was carried out in a number of countries
situated at different latitudes.
In the present study it was hypothesized that dark and/or windowless, indoor spaces
and lack of colour will have a depressing influence on the mood of people in those spaces.
It was further hypothesized that the seasonal variations in length of day may modify the
mood of people working indoors, with a negative impact during the dark season, and that
the impact on mood might be mediated by individual characteristics, such as age and
gender.
3. Method
3.1. Participants, settings and climatic conditions
The study was part of an international project carried out in real work environments at
different times of the year in four different countries with different latitudes (Argentina,
Saudi Arabia, Sweden and the UK). Employees at a number of larger, as well as smaller,
indoor work environments (offices, schools and industrial premises) were included in the
study. The sampling criteria included male and female personnel generally working at
least three-quarters of full time, during daytime. Night-shift workers were excluded and
so were those with previous records of prolonged illness. A total of 988 persons (468
females and 520 males) aged 18 to 65 years completed all parts of the study (mean 39.4
SD 9.85 years), (table 1).
The Swedish sites were situated in the southern part of the country (568N), where the
length of day varies between 7 h during winter and more than 17 h during summer. In the
UK the sites were in the southern part (528N) with a length of day that varies between
8 h in winter and more than 16 h in summer. In Saudi Arabia, the sites were in the
Greater Dammam area, by the Arabian Gulf in the eastern part of the country (268N).
The length of day varies from 10.5 h in winter to almost 14 h in summer. In Argentina,
the study was carried out in Tucuman in the northwestern part of the country (278S). The
length of day varies between 10.5 and almost 14 h. The difference in day length between
summer and winter varied from more than 10 h in Sweden to only 3.5 h in Argentina and
Saudi Arabia.
3.2. Procedure
A questionnaire consisting of seven or eight pages was used in this study. Most of the
scales had been pre-tested in a pilot study at three Swedish hospitals. The questions
were originally drafted in English, then translated into Swedish, Arabic and Spanish and
Table 1. Number of participants and dropout.
Country
Approached
(n)
Took part at
least once (n)
Initial dropout
(%)
Took part on
all occasions (n)
Lost in follow-up
(%)
Argentina 308 303 2 222 27
Saudi Arabia 369 324 12 253 22
Sweden 661 609 8 406 33
UK 239 229 4 107 53
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¨ller et al.
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re-translated to English for a final check. In Saudi Arabia, both English and Arabic
versions were used. The questionnaires were administered to the participants on five
different occasions during one of 2 consecutive years, including both the light and dark
seasons. In Sweden, the UK and Saudi Arabia the data collection took place in the
middle of September, December, February, April and June, whereas in Argentina the
corresponding months were March, June, August, October and December. Great care
was taken to avoid vacations and religious holidays, as well as shifts between standard
time and daylight saving time. With regard to the provision of siestas in Saudi Arabia and
Argentina, all participants were requested to answer the forms at 11.00 hours and because
the answers should reflect the conditions at work, Tuesdays and Wednesdays were
selected as alternative days. If for various specified reasons a participant was not well or
fit, the form could be answered 1 week later. Indoor lighting was measured at each
workplace. Additional information was obtained from meteorological data.
3.3. Self-reported mood
Based on concepts brought from neuro-psychology, the emotional well-being of the
participants was assessed with the following 12 scales: rested/tired; alert/drowsy; awake/
sleepy; interested/bored; efficient/inefficient; devoted/indifferent; secure/anxious; friendly/
angry; happy/sad; confident/hesitating; independent/dependent; strong/weak (Ku
¨ller
1991). Each of the four-grade rating scales was to be answered in terms of ‘How did you
feel most of the time during the last few days?’ The scales were combined into a total
index of emotional status (coefficient a¼0.82).
3.4. Appraisal of the visual environment
The current lighting conditions in the workplace were assessed by the participants on a four-
graded scale including the following steps: 1) clearly insufficient, much too dark; 2) slightly
insufficient, a little bit too dark; 3) just right, neither too bright nor too dark; 4) very bright
and glaring, too much light (between seasons consistency coefficient a¼0.82). The interior
decoration was assessed on a similar scale including the steps: 1) no colour at all, very
subdued and monotonous; 2) colours are rather neutral; 3) some colour but not very vivid;
4) very colourful and vivid (between seasons consistency coefficient a¼0.86). In addition,
the subjects estimated the physical distance from their workplace to the nearest window.
3.5. Measurements of indoor lighting
Physical light measurements in terms of horizontal illuminance values (lux) were carried
out with calibrated luxmeters in the rooms or spaces where the subjects worked. The
measurements, which were carried out around noon with a clear or light overcast sky,
were functionally related to the subject’s work site, that is, if the person normally was
sitting at a desk, the luxmeter was placed on the desktop in front of the person. The
artificial illumination was generally left on, provided this was normal for that time of the
year. However, all kinds of desktop lamps were turned off during measurements.
3.6. Meteorological data
Length of day was computed from sunrise to sunset for each region at five times of the
year corresponding to the times of data collection.
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3.7. Statistics
The data were treated by means of parametric statistical tests such as Pearson correlation
and ANOVA (Norusis and SPSS Inc. 1993). The data treatment was based on those
participants who took part on all five occasions. In analyses related to the impact of age,
the participants were partitioned into two groups of equal size, younger (18–38 years) and
older (39–65 years). The data from the Argentinean study were recoded in order to
correspond to the data from the northern hemisphere. Due to the large number of
comparisons the statistical level of acceptance was set to p¼0.01.
As a special precaution, the partial dropout group was compared in a number of
respects to those who completed the study. Out of a total of 17 statistical comparisons,
including age, gender and emotionality, none reached the stipulated significance level.
Amongst those who completed the study missing values on the separate scales generally
amounted to less than 1/1000 in Saudi Arabia and Sweden, 3/1000 in the UK and 1/100 in
Argentina. These missing values were replaced by total mean or median values in a
conservative way in respect of the various hypotheses.
4. Results
The indoor environments in the vast majority of cases consisted of cell offices and open-
plan offices, illuminated by fluorescent lamps, and most of the personnel worked with
visual display units. In addition there were some factory plants with large open areas lit
by high-pressure sodium lamps. The distance between the individual workplace and the
nearest window varied from less than 0.5 to 100 m with a median value of 2.0 m (table 2).
The indoor illuminance values were mostly higher during the summer than the winter
months (table 3). Deviations from this pattern generally depended on the use of curtains
and other shading devices in order to avoid excessive heat and annoyance from direct
sunlight. This was specially so in Argentina, where illuminance was often lower than the
values recommended by the common standards for office tasks, that is, 500 lux.
Table 2. Distance from workplace to nearest window (n ¼988).
Distance (m) 0–1.0 1.1–2.0 2.1–5.0 5.5–10 11–100
Work sites (%) 28.5 25.0 25.4 9.6 11.5
Table 3. Illuminance values (lux) at workplaces during different seasons.
Country
February
(August)*
April
(October)*
June
(December)*
September
(March)*
December
(June)*
Argentina Mean 309 316 368 265 277
n¼222 SD 135 145 183 95 134
Saudi Arabia Mean 429 487 534 345 420
n¼253 SD 211 236 272 167 302
Sweden Mean 643 658 751 621 465
n¼406 SD 170 269 276 188 92
UK Mean 579 869 517 572 364
n¼107 SD 74 419 190 94 57
*The corresponding month in Argentina.
1500 R. Ku
¨ller et al.
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In 2% of all responses the participants experienced the lighting conditions at their
workplace as much too dark, whereas in 15% they were considered a little too dark, in
74% as just right and in 9% as too bright. About 14% thought the colours were very
subdued, 60% considered them to be neutral, 22% reported some colour and 5% thought
their workplace was very colourful. The inter-correlations between the different estimates
of the visual environment were mostly low. There was a modest negative correlation
between workplace illuminance and the distance to the nearest window, which varied
between r ¼70.18 and r ¼70.27 for the different occasions (n ¼988, p50.01). The
correlation was most pronounced during the summer season.
Before looking into the major hypotheses, a multivariate ANOVA with repeated
measures (occasion) was carried out with gender, age and country as grouping factors,
and with the emotional responses of the participants as the dependent variable. There
were minor differences between males and females (F(1, 972) ¼6.72, p50.01) and
between the younger and older participants (F(1, 972) ¼6.69, p50.01). There were also
differences between the four countries; however, since this may reflect semantic
differences in the translated scales, these will not be reported in detail. (The seasonal
effect for each country will be discussed below.)
In addition to the main effects, there were interactions between season and country
(p50.001), between age and country (p50.001), between gender and country (tend) and
between age, gender and country (p50.01). As seen in table 4, the male participants in
Argentina and Saudi Arabia reported more well-being than the females, and in Saudi
Arabia the older participants reported more well-being than the younger ones. There
were no significant interactions between age and gender, on one hand, and season, on
the other.
To investigate whether seasonal variations in length of day will modify the mood of
people working indoors, separate ANOVA with repeated measures were carried out
for each country. As seen in figure 1 there were considerable seasonal differences in
Sweden (F(4, 1620) ¼46.2, p50.001) and in the UK (F(4, 424) ¼6.70, p50.001)
with positive values in summer and negative values in winter. In Argentina and Saudi
Arabia the seasonal differences were much smaller, with somewhat depressed values
in summer, but these variations did not reach significance. In addition to the
total emotional index, separate analyses were carried out for the sub-scales. All in all,
these analyses rendered little new information. However, the scales related to
arousal were somewhat more differentiating than the other scales. In Sweden and the
UK the participants felt considerably more tired, drowsy and sleepy during the winter
season.
In order to test the hypotheses that light and colour in the workspaces will influence the
mood of people working there, a number of analyses were performed with the index of
emotional status as the dependent variable (table 5).
Table 4. The index of emotional status for different sub-groups in the four countries.
n Males Females Younger Older Total
Argentina 222 2.98 2.84 2.93 2.92 2.92
Saudi Arabia 253 3.09 3.00 2.96 3.21 3.04
Sweden 406 2.95 2.93 2.92 2.95 2.94
UK 107 2.71 2.70 2.71 2.70 2.71
Total 988 2.96 2.91 2.91 2.96 2.94
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A two-way ANOVA with illuminance and distance to nearest window as grouping
factors was performed separately for each occasion. Illuminance was partitioned into three
groups (28–300, 301–600, 601–2150 lux) and distance into four groups (0–2, 2.1–5, 5.5–10,
11–100 m). The impact of illuminance on the participants’ mood was not significant at any
time and there were no significant interaction effects. The distance to the nearest window,
on the other hand, had a significant impact on mood in February (August in Argentina;
F(3, 976) ¼5.90, p¼0.001) and there were similar tendencies in April (October; p¼0.06),
June (December; p¼0.03) and September (March; p¼0.08). Figure 2 shows that distances
up to 2 m from the window had the most beneficial effect on the emotions. However, being
very far from a window seemed better than being 5–10 m away.
Concerning subjective lightness a one-way ANOVA was performed for each occasion.
As shown in table 6, the participants’ emotional status was at its highest when the
lightness was considered to be just right.
Concerning interior decoration, the ratings of each individual were averaged over the
five occasions and partitioned into three groups with no colour (22%), neutral colour
Table 5. Means and standard deviations of the dependent and independent variables (n ¼988).
February
(August)*
April
(October)*
June
(December)*
September
(March)*
December
(June)*
Emotional index Mean 2.90 2.94 2.97 2.97 2.89
SD 0.45 0.44 0.47 0.42 0.45
Illuminance (lux) Mean 506 560 584 465 400
SD 215 311 291 221 191
Distance to window Mean 8.08 8.67 9.14 8.78 9.21
SD 19.9 21.0 22.0 21.2 22.0
Subjective lighting Mean 2.90 2.92 2.93 2.88 2.87
SD 0.54 0.53 0.53 0.57 0.55
Subjective colour Mean 2.20 2.18 2.23 2.14 2.17
SD 0.72 0.69 0.69 0.78 0.73
*The corresponding month in Argentina.
Figure 1. There were large seasonal differences in Sweden and the UK, whereas in
Argentina and Saudi Arabia the differences were much smaller (In Argentina the
corresponding months were July through June. Notice that the figures cover only the
central portion of the index scale 1–4).
1502 R. Ku
¨ller et al.
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(53%) and some or much colour (25%). These groups were then entered into an ANOVA
with repeated measures for the different seasons. In addition to the seasonal effect
(F(4, 3940) ¼9.02, p50.001) there was a highly significant difference in mood between
the three groups (F(2, 985) ¼18.9, p50.001). As seen in figure 3, the index of emotional
status was higher throughout the year for those who had the most colourful work
environment. The interaction between season and decoration was not significant.
5. Discussion
It was felt that the varied locations of the testing sites and the care taken in sampling and
data collection, together with the low dropout rate, provided a satisfactory testing ground
for the hypotheses. Apart from minor differences, males and females responded in a
similar way and so did the younger and older personnel. Replicating a study in countries
with different cultures and languages makes comparisons in absolute figures difficult. This
was considered in the experimental design by repeating the measurements on five
occasions covering a total period of 1 year.
All the results clearly point to the existence of an interaction between season and
country, which could be ascribed to variations in day length. In the countries situated far
north of the equator there was a strong and highly significant variation in psychological
mood over the year that did not occur in the countries closer to the equator. These mood
Table 6. The participants’ emotional status as a function of subjective lightness (n ¼988).
February
(August)*
April
(October)*
June
(December)*
September
(March)*
December
(June)*
Much too dark 2.72 2.78 2.80 2.90 2.60
A little too dark 2.79 2.90 2.89 2.89 2.77
Just right 2.93 2.96 3.00 3.01 2.94
Too much light 2.86 2.88 2.88 2.83 2.76
F(3, 987) ¼5.15 2.05 4.09 7.82 12.1
Significance p¼0.002 p¼0.105 p¼0.007 p50.001 p50.001
*The corresponding months in Argentina.
Figure 2. The distance to the nearest window had a significant impact on mood in
February (August in Argentina), and there were similar tendencies at three of the other
four occasions.
The impact of light and colour on psychological mood 1503
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swings of personnel working indoors may partly be related to the amount of daylight
through the windows. They may also reflect more basic seasonal variations of sub-SAD
(Ku
¨ller and Ku
¨ller 2001, Veitch et al. 2004).
Theories of emotion are as old as psychology itself, or even older, and many different
attempts at conceptualizing and measuring emotions have been made. Environmental
psychology has generally taken a dimensional approach to the study of emotions (the
HEI-model; Ku
¨ller 1991). In the present study mood was assessed in terms of one total
index of emotional status. Analysed one by one, the different mood scales generally
behaved in a consistent way, which means that light and colour influenced a wide range of
emotions in a similar way, making people feel, for instance, more alert, interested,
friendly and confident. The only exception was the scales related to arousal, which
declined more than the other emotional qualities when the days were at their shortest. As
an example, tiredness increased more than sadness.
Among the more striking findings in the study is the considerable variation of the
indoor illuminance, ranging from below 30 lux to well above 2000 lux. In all four
countries, a large proportion of the observed values fell below the recommendations
given in contemporary lighting manuals (Rea 2000). In view of this, it may seem
remarkable that the vast majority of the studied subjects perceived the lighting conditions
at their workplace as ‘just right’. The lighting was thought to be ‘much too dark’ in only
2% of all responses. The difficulties in establishing objective criteria for good lighting are
further illustrated by the rather low correlations between the different lighting measures.
Most lighting engineers nowadays are aware of the complexity inherent in any lighting
situation and the necessity to also consider its qualitative aspects.
When all four countries were considered together, it became evident that the light and
colour of the workplace itself had an influence on the mood of persons working there.
Perhaps somewhat amazing, the illuminance as measured in objective terms showed no
significant impact on mood at any time of the year. Horizontal illuminance values had
been obtained at each workplace under realistic, still standardized, conditions. In spite of
large variations in absolute lux values there were no corresponding effects on mood. This
is contrary to the results of some earlier studies, where such effects were found (e.g.
Daurat et al. 1993, McCloughan et al. 1999). However, most of these studies were made
in the laboratory and not in real environments. In addition to illuminance it might be
useful to include various measures of luminance.
Figure 3. The mood was better throughout the year for those who had the most colourful
work environment.
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¨ller et al.
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On the other hand, the distance to the nearest window had a significant impact on
mood in February (August in Argentina) and there were similar tendencies on three of
the other four occasions. This distribution was bimodal with one peak when the distance
was 0–2 m and another when the window was far away (410 m), actually so far that the
workplace in practice was windowless. This latter peak might represent an adjustment to
windowless environments, and, as such explain at least in part, the conflicting results in
some of the earlier studies (Ku
¨ller and Wetterberg 1996). It must be emphasized that the
view function of windows is very different from the daylight delivery function. It has been
suggested that, to satisfy most workers, windows should cover at least 20% of the
window wall area (Rea 2000). In addition, tinted glass and the use of various shading
devices might also have a slight emotional impact (Bu
¨low-Hu
¨be 1995).
Another non-linear relationship concerned subjective lighting. The psychological mood
was at its lowest when the lighting was experienced as much too dark. The mood then
improved and reached its highest level when the lighting was experienced as just right, but
when it became too bright the mood declined again. This result is hardly astonishing.
However, it indicates the usefulness of subjective lighting assessments in field studies of
the present kind, where objective lighting measurements might be complex and time-
consuming or not available. In this context it may be tempting to quote an old study by
Flynn (1977), where he lists four characteristics of lighting of importance for subjective
impressions: overhead/peripheral; bright/dim; uniform/non-uniform; visually warm/cool.
Finally, the colour of the workspace stands out as rather important. The index of
emotional status was higher throughout the year for those who had the most colourful
work environment. Thus, it may seem that the brighter the colour, the better it is for
those who work there. However, this should be seen in the light of the fact that the
majority of the environments were subdued or neutral. Only 5% were experienced as very
colourful. In some laboratory studies of colour and mood, very strong colours were
applied with results that seemed undesirable (e.g. Ku
¨ller and Mikellides 1993, Kwallek
et al. 1996). To apply highly saturated colours in real environments, thus, might not be a
good solution. Still, it is suggested that a moderate increase in the use of good colour
design will serve to improve the overall mood of the working staff.
In conclusion, human emotions are influenced by a number of factors and only part
of them might be related to the conditions at work. In this perspective the impact of
light and colour found in this study certainly seems large enough to warrant increased
attention. For the practitioner it will be important to consider both the seasonal impact
and the access and distance to windows. Physical measurements should be supple-
mented by qualitative assessments by those directly concerned. There is also need for
continued research on a longitudinal basis. A better understanding will demand the
setting up of long-term quasi-experimental field studies that will allow a more detailed
analysis of several different lighting parameters. Furthermore, light and colour should
be treated as part of a more complex system making up the totality of a healthy
building.
Acknowledgements
The Swedish part of the study was supported by the Swedish Council for Building
Research and the Swedish Council for Work Life Research. The replication in the UK
gained financial support from Oxford Brookes University and in Argentina from the
Research Council of the University of Tucuman. The authors gratefully acknowledge the
assistance of Wakefield Carter and the cooperation of all personnel, heads and managers
The impact of light and colour on psychological mood 1505
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who took part in or supported this study. We also wish to convey our thanks for the
valuable suggestions provided in the peer review.
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