Measuring the Emotional and Physiological Effects of

Light and Colour on Space Users

Nadeen Abbas

, Dinesh Kumar

and Neil Mclachlan

School of Electrical and Computer Engineering,

RMIT University,

PO Box 2476V

Melbourne,

Australia - 3001

bstract. Colour and light are known to have an impact on our health and well-

being. While large resources are allocated for well designed buildings with the

right choice of colours and lighting conditions, there is little scientiﬁc evidence

that supports these choices. The aim of this research was to determine the impact

of different colours and lighting conditions on people, using non-invasive means.

Close correlations between skin conductance (SC), our emotions and health are

well reported in literature and hence these are expected to be good measures of

the environmental conditions on people.

1 Introduction

There are numbers of factors in a constructed environment that inﬂuences the psycho-

logical and emotional state of the users in that space. Light intensity and colour are

two important factors with impact on users’ performance in the space. While people

are known to adapt to different environments, the different conditions have an impact

on their productivity and general wellbeing. For effective usage of our buildings, it is

important to have an objective measure of these factors on the health and wellbeing of

human.

The literature on light and colour is extensive, however a uniform set of ﬁndings is

lacking for a consistent perspective on the inﬂuence of colour and light. There are num-

bers of publications that report the research conducted to determine the effect of various

lighting and colour conditions on peoples’ emotions. Most of these are based on subjec-

tive measures [1], [2], [3], [4]. The subjects complete questionnaires to describe their

feelings after being exposed to different colour and lighting conditions. Research con-

ducted by Karrie on interior design for ambulatory care facilities reports some important

design factors. The research reports that colour and lighting have profound inﬂuence on

patients and consumers satisfaction, stress level, health and wellbeing. The paper also

reports that the effects of colour and lighting are inseparable and lighting intensity af-

fects the perception of colour [5].

Abbas N., Kumar D. and Mclachlan N. (2005).

Measuring the Emotional and Physiological Effects of Light and Colour on Space Users.

In Proceedings of the 1st International Workshop on Biosignal Processing and Classiﬁcation, pages 78-86

DOI: 10.5220/0001194200780086

 SciTePress

The research by Igor Kenz reports subjective tests to study the effects of the rec-

ommended ofﬁce lighting on mood and cognitive performance. The work demonstrates

that the physical setting of an ofﬁce and the use of artiﬁcial light can have a signiﬁcant

impact on the mood of the inhabitants [1]. Another research conducted by Warren E.

Hathaway has found that students who study under daylight like light were less absent

and achieved higher scores than those working under yellowish-orange sodium vapour

bulbs [4].

However the outcome of subjective tests is uncertain. It has been reported that sub-

jective tests such as questionnaires are insufﬁcient and may be misleading especially

when conducted at the end of the experiment [6], [7]. Often, participants may mix their

emotions between the start and the end of experiments, and the recollection of a series

of emotions that occurred earlier may lack accuracy.

Peter J. Lang said that emotion manifests itself in three separate aspects of people;

(i) physiological, (ii) psychological (i.e. subjective experience) and (iii) behavioural.

The physiological is the change in the physical properties of the person, psycholog-

ical being the subjective experience while the behavioural is manifest by the physical

actions such as approach and avoidance, and each of these associated with speciﬁc mea-

sures [6], [7]. The paper also suggests that it is necessary not to limit the studies to the

assessment of a single response but include sample measures from each of the three

manifestations.

Research was conducted by Binjamin to identify the impact of short ﬁlm clips (6s)

on people, where some of these clips were coloured and some were black and white.

Skin conductance, heart rate and facial movement were used in the research as physio-

logical measures in addition to subjective tests to study the short term effect of colours

on people. The results indicated that colour has a small effect on the subjective ex-

perience but did not exert a main effect on the skin conductance response. The paper

recommended further studies to explore the impact of colour and light on physiological

measures using stimuli of longer time durations [8].

The authors are unable to ﬁnd any research that has measured the physiological

changes in people due to light and colour stimuli of long duration. To identify the best

choice of interior conditions for buildings there is a need to determine the physiological

changes in people under these conditions. The reasonably long exposure is to allow the

participants of the study to adapt to the conditions.

1.1 Skin Conductance and Emotions

Skin conductance (SC) is one of the fastest responding non-invasive measures of auto-

nomic nervous system activity. It is a method of capturing the autonomic nerve response

as a parameter of the sweat gland. Physically SC is a change in the electrical properties

of the skin in response to different kinds of stimuli. The response is measured by the

change in voltage from the surface of the skin [9].

The close correlation between SC and emotions is well documented in the literature.

Lane reported that SC shows different values for different emotions when studying the

effects of emotional valence, arousal and attention on neural activation during visual

processing of pictures [10]. Storm also reported that SC ﬂuctuations are a measure of

preoperative stress [11]. Healy used SC as a measure of the emotional stress developed

during driving [12]. Heo used SC as a measure of emotional response to web advertising

[13].

The aim of this research was to provide a deﬁnitive answer for the choice of light

and colour conditions in a constructed environment for the betterment of health and well

being of the occupants. This paper reports experimental research conducted to identify

the physiological changes when exposed to different light and colour conditions. For

this aim, the paper reports changes in the SC of people when exposed to different colour

and intensity lights for periods of time that allowed the participants to adapt to the

conditions.

The research has been built on the current body of knowledge that physiological

measures are necessary to measure the effects of light intensity and colour on people to

ensure objectivity and reproducibility of the experiments. This would remove the short-

comings of earlier research where questionnaire-based and other subjective experiments

were used for identifying the effect of colour and light conditions. The aim is to help

provide an objective rational for the choice for light intensity and colour by architects

for different buildings.

2 Methodology

To determine the physiological changes due to the exposure of people to different light

and colour conditions, it was important to conduct controlled experiments where all

other conditions were kept constant. This was necessary to ensure that the changes

recorded were due to the effect of light and colour conditions only. To measure the

physiological changes, experiments were conducted where measurable changes in SC

were recorded in response to change in colour and intensity of light.

2.1 Subjects

The experiments were conducted on 15 healthy subjects comprising 3 males and 12

females. They were not under any medication that may affect their mental and neural

activities. The participants were recruited with the help of posters and most were uni-

versity students. Their participation was voluntary. Ethics approval for the experiments

was obtained and subjects completed consent forms before the experiment. Subjects

were made aware of the details of the experiments and were also informed that they

could stop the experiment if they chose to.

2.2 Experimental set up

The experiments were conducted in a neutrally coloured and furnished multi-user lab-

oratory approximately 10m x 4m in size. Subjects were seated comfortably facing a

1.5m x 2m white non-reﬂecting screen approximately 1.5m away from the chair. Envi-

ronmental conditions such as air temperature and humidity, furniture and layout setting

were kept constant. All experiments were conducted in a quiet laboratory early in the

morning to exclude noise disturbance and circadian rhythms as potential confounds.

The order and interval of exposure to lights were kept constant for all subjects. The

participants were exposed to the different light and colour conditions by illuminating

the screen with ﬂoodlights that had globes of green, red and blue colours. The light

conditions were recorded using LUX and FC light meter. During the experiments, the

participants were exposed to eight different colour and light intensities which are de-

scribed in table 1. The duration of the complete experiment was approximately 110

minutes. In preliminary experiments it was observed that eight minutes were sufﬁcient

to ensure that the participants adapted to the light and colour. Skin conductance was

recorded for two minutes after the eight minutes had elapsed.

Table 1. Intensities of coloured lights used.

Colour of lights Intensity of light/ lux

White 207

Blue low 28

Blue high 48

Green low 90

Green high 169

Red low 92

Red high 157

Natural 20 - 105

At the start of the experiment, the ﬁngers were prepared for recording SC using

wipes. Two electrodes were wrapped around two ﬁngers in the right hand for the dura-

tion of the complete experiment. The subjects’ SC was recorded in the last 2 minutes of

each coloured light. The signals were recorded using Amlab biosignal recording equip-

ment with sampling rate of 200 samples/second. The quality of signals was visually

monitored at the start and during the experiment. The data was saved as text ﬁles and

analysed using Matlab. A three minutes break was given to the subjects after each light

condition where they were allowed to relax and move. During the experiment, the par-

ticipants were engaged in continuous and pre-prepared non-controversial discussions on

the history of architecture so as to reduce stress due to boredom. The style of speaking

was maintained constant to avoid the sound and conversation related variations during

the experiments.

3 Results and Discussion

In this section the results of the experimental data have been analysed. Skin conductance

of the human body has continuos variation over time even when there are no external

stimuli. The aim of this research was to identify the changes in SC due to the lighting

and colour conditions. For this aim the values of SC were recorded for 2 minutes under

each colour and intensity light for all the subjects. These recordings were graphed for

each subject; the graph for subject 10 is shown as an example in ﬁg 1.

The values of SC were then averaged over the two minutes for each colour and

lighting condition. The mean and the standard deviation of SC values for the two minute

0 0.5 1 1.5 2 2.5 3

x 10

Samples

Skin conductance, micro siemens

Green low

Red low

Red high

Natural

Blue high

White

Blue low

Green high

Fig.1. Skin conductance for subject 10 under different colour lights

recording were tabulated and are shown in table 2. The SC under white light was then

taken as a base level for each subject and SC readings under all other colour lights were

compared to it. Subtracting the mean SC under white light from each coloured light

provided these ﬁgures; the results were tabulated and are shown in table 3. The results

were also normalised for each subject by taking the mean SC under white light as a

reference, the results were tabulated and are shown in table 4.

The difference in mean SC, obtained from table 3, was then put into bar charts for

comparison. An example for subject 10 is shown in ﬁg 2.

As can be seen from table 2, there are changes in SC under different colour and

intensity lights. From tables 3 and 4, it has been observed that 60-73% of the non-white

conditions caused higher skin conductance than white conditions. It is also noted that

some colours caused greater change in SC than other colours. Natural light caused the

largest increase in SC for 20% of the subjects and the largest decrease in SC for 20%

of subjects. Green high light caused the largest increase in SC for 13% of the subjects

and the largest decrease in SC for 13% of the subjects. Red high light caused the largest

increase in SC for 20% of the subjects and blue low light caused the largest decrease in

SC for 20% of the subjects.

It has also been observed that the direction of change in SC (increase or decrease)

is subject dependent, where the same colour and intensity light can cause an increase

in SC for some subjects and a decrease in SC for others. However it is also noted from

the results that the inter subject variation is large. That can be seen clearly from the last

rows in tables 3 and 4 where the variation in SC between different colour and intensity

lights is relatively small compared to the inter subject variation.

T-test was conducted to determine if the change in mean SC due to different colour

and intensity lights is signiﬁcant. The results are shown in table 5.

Table 2. Mean Skin Conductance values.

Subj W light BL light BH light GL light GH light RL light RH light N light Mean SD

1 20.38 13.65 16.18 19.95 13.59 19.61 20.38 21.34 18.14 3.17

2 7.9 9.31 7.64 6.8 6.22 6.13 5.22 6.09 6.91 1.30

3 16.5 27.12 26.54 99.91 99.92 64.62 17.36 41.39 49.17 34.90

4 60.7 61.22 59.12 56.72 54.61 53.1 51.89 51.05 56.05 3.99

5 9.14 12.71 11.09 10.49 11.37 8.58 10.07 7.45 10.11 1.68

6 13.99 15.55 23.77 31.24 16.85 18.5 21.81 25.25 20.87 5.77

7 27.13 50.31 49.95 39.22 43.57 55.28 53.89 69.56 48.61 12.48

8 55.74 25.6 65.09 47.32 90.25 99.92 99.92 99.92 72.97 28.63

9 30.44 15.06 13.88 43.02 38.7 33.98 45.66 37.46 32.28 11.97

10 6.05 5.75 6.38 9.41 5.36 8.51 7.96 11.47 7.61 2.12

11 40.04 55.35 50.35 51.93 57.88 59.87 63.02 47.25 53.21 7.42

12 25.04 28.55 30.77 35.59 37.57 35.05 42.08 35.96 33.83 5.42

13 38.2 74.78 64.01 23.62 28.94 29.13 24.36 40.91 40.49 19.05

14 7.46 7.07 6.84 6.63 7.61 7.78 6.72 5.68 6.97 0.67

15 8.1 9.6 9.42 10.07 11.57 11.33 11.14 10.52 10.22 1.17

Mean 24.45 27.44 29.40 32.79 34.93 34.09 32.10 34.09 - -

SD 17.65 22.24 22.23 25.33 30.07 27.41 26.86 26.42 - -

Table 3. Difference in mean skin conductance.

Subj W light BL light BH light GL light GH light RL light RH light N light Mean SD

1 0 -6.73 -4.2 -0.43 -6.78 -0.77 0.01 0.97 - 2.56 3.17

2 0 1.4 -0.26 -1.11 -1.69 -1.77 -2.68 -1.81 - 1.13 1.30

3 0 10.62 10.04 83.42 83.42 48.13 0.86 24.89 37.34 34.90

4 0 0.52 -1.58 -3.98 -6.09 -7.6 -8.81 -9.65 - 5.31 3.99

5 0 3.57 1.95 1.35 2.22 -0.57 0.93 -1.69 1.11 1.68

6 0 1.56 9.78 17.25 2.86 4.51 7.83 11.26 7.86 5.77

7 0 23.18 22.82 12.09 16.44 28.15 26.76 42.43 24.55 12.48

8 0 -30.14 9.36 -8.41 34.51 44.18 44.18 44.18 19.69 28.63

9 0 -15.38 -16.56 12.58 8.25 3.54 15.21 7.02 2.09 11.97

10 0 -0.3 0.32 3.36 -0.7 2.45 1.9 5.42 1.78 2.12

11 0 15.31 10.3 11.89 17.84 19.83 22.97 7.21 15.05 7.42

12 0 3.51 5.73 10.55 12.53 10.01 17.05 10.92 10.04 5.42

13 0 36.58 25.81 -14.58 -9.27 -9.07 -13.84 2.7 2.62 19.06

14 0 -0.39 -0.62 -0.83 0.16 0.32 -0.74 -1.78 - 0.55 0.67

15 0 1.49 1.32 1.97 3.47 3.23 3.04 2.42 2.42 1.17

Mean - 2.99 4.95 8.34 10.48 9.64 7.64 9.63 - -

SD - 15.38 10.50 22.50 23.17 17.64 15.10 15.75 - -

Table 4. Normalised values of mean skin conductance (white light as reference).

Subj W light BL light BH light GL light GH light RL light RH light N light Mean SD

1 1 0.67 0.79 0.98 0.67 0.96 1.00 1.05 0.87 0.16

2 1 1.18 0.97 0.86 0.79 0.78 0.66 0.77 0.86 0.17

3 1 1.64 1.61 6.06 6.06 3.92 1.05 2.51 3.26 2.12

4 1 1.01 0.97 0.93 0.90 0.87 0.85 0.84 0.91 0.06

5 1 1.39 1.21 1.15 1.24 0.94 1.10 0.82 1.12 0.19

6 1 1.11 1.70 2.23 1.20 1.32 1.56 1.80 1.56 0.39

7 1 1.85 1.84 1.45 1.61 2.04 1.99 2.56 1.91 0.36

8 1 0.46 1.17 0.85 1.62 1.79 1.79 1.79 1.35 0.54

9 1 0.49 0.46 1.41 1.27 1.12 1.50 1.23 1.07 0.42

10 1 0.95 1.05 1.56 0.89 1.41 1.32 1.90 1.29 0.36

11 1 1.38 1.26 1.30 1.45 1.50 1.57 1.18 1.38 0.14

12 1 1.14 1.23 1.42 1.50 1.40 1.68 1.44 1.40 0.18

13 1 1.96 1.68 0.62 0.76 0.76 0.64 1.07 1.07 0.54

14 1 0.95 0.92 0.89 1.02 1.04 0.90 0.76 0.93 0.09

15 1 1.19 1.16 1.24 1.43 1.40 1.38 1.30 1.30 0.11

Mean - 1.16 1.20 1.53 1.49 1.42 1.27 1.40 - -

SD - 0.44 0.38 1.31 1.30 0.78 0.42 0.59 - -

1 2 3 4 5 6 7 8

−1

Colour of lights

Change in SC, micro siemens

Subject 10

White

Blue low

Blue high

Green low

Green high

Red low

Red high

Natural

Fig.2. Difference in mean skin conductance compared to white light for subject 10

Table 5. T-test for change in mean skin conductance.

colour of light t-value p-value

Blue low -0.408 0.6904

Blue high -0.675 0.5107

Green low -1.046 0.3054

Green high -1.164 0.2634

Red low -1.145 0.2626

Red high -0.921 0.368

Natural -1.174 0.2559

The t-test shows a high p-value under all colour lights (p > 0.05) which means that

the variation of SC in response to colour and lighting conditions is not signiﬁcant.

The results show that there is a change in SC under different colour and intensity

lights. Results also show that some colours and intensities caused greater impact on the

SC of participants than others. Since SC is associated with arousal of the participants,

from the experiments we can see that white light caused the most relaxed state (lowest

SC) in 2/3 of the experiments. However it is also observed that the inter subject varia-

tion in SC is relatively high in the 15 participants. That is also conﬁrmed in the t-test

which shows that the change in SC in response to different colour and intensity lights

is not signiﬁcant. From the above it is not possible to co-relate the changes in SC to the

speciﬁc colour and intensity lighting conditions.

Previous research reported by Binjamin [8] reported that short term colour exposure

(6 seconds) did not exert a main effect on the skin conductance response. This research

demonstrates that there is a change in SC when people are exposed to different colour

and lighting conditions for longer periods of time (10minutes). However the inter sub-

ject variation is very large which makes it hard to co-relate the changes in SC to the

speciﬁc colour and lighting conditions.

4 Conclusion

This research investigates the emotional and psychological effects of different colour

and lighting conditions on people. It reports changes in the SC of 15 subjects when ex-

posed to different colour and intensity lights. The research demonstrates that the change

in colour and intensity of light caused a change in SC. It also shows that some colours

have greater impact on SC than others. In most experiments (2/3 of the experiments)

white light caused the lowest SC, which means that it provided the most relaxing con-

dition. However the hypothesis t-test analysis for change in mean SC due to different

colour and intensity lights indicated that the changes in SC are not signiﬁcant, that is

due to the large inter subject variation. The research has not studied the difference be-

tween the response to different colour and intensity lights based on gender and age [14],

the authors would recommend that further experiments would take that into account.

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