1. M. L. Theeman Ian Davies Department of Psychology University of Surrey
Reactions to
Fluorescent Light Pairs
Indication of An Across-Participant Pattern of Light Preference?
M. L. Theeman Ian Davies Department of Psychology University of Surrey

2. Why? Lighting makes a difference –
But our lighting ‘needs’ vary alongside specific
environmental, individual, and social factors

3. Basis for Research
Can we integrate user demographics and task variables into a formula to predict optimal lighting levels for specific workplace populations based on preference measures?

4. Statement of Purpose
To investigate the extent to which preferences for certain qualities of fluorescent light may indicate a pattern of preference across-participants which is positively associated with well-being and productivity.

5. Definitions Brightness Light Quality ◦ Absence of flicker
◦ Color rendition (CRI)
◦ Distribution of light
◦ Correlated color temperature (CCT)
Daylight
5000K
Cool
4000K
Warm
3000K

6. Research Roots

7. Previous Research Duration of Exposure Health and Performance
Heil & Mathis 2002
Health and Performance
Hathaway 1995, Heschong Mahone Group 1999
Depression and Light Perception
Friberg & Borrero 2000
Individual Sensitivities to Light
Heerwagen 1990

8. Research Questions
To what extent are daylight-simulating fluorescents preferred over other fluorescent tubes?
Will favored factorial combinations of CCT and brightness vary by gender?
Will the absence of visual stimuli affect preference?

9. Methodology 21 light combinations Two trials per participant
Familiar room in building
60 office-based employees
38 male female
Tested for color-blindness
21 light combinations
Daylight 12” 9”
Warm 12” 9”
Cool 12” 9”
Two trials per participant
Color panel for visual stimuli

10. Significant Mean Preference Scores
White Trial
Color Trial
Mean
Score t
Sig.
(2-tailed)
12” Daylight
3.00
2.32
.024 *
2.92
2.06
.044 *
12” Cool
2.77
-5.86
<.001***
2.90
-3.29
.002 **
12” Warm
1.58
0.44
.661
1.87
1.38
.174
9” Daylight
2.03
-4.77
2.28
-4.28
9” Cool
2.58
-2.70
.009 **
2.73
-1.07
.291
9” Warm
1.52
.133
1.65
1.91
.061
* p<.05
**p<.01
***p<.001

11. Mean Preference Score by Gender
White Trial R A N K
Color Trial
Female
Male
12” Daylight
2.55
3.26 1
2.77
3.00
12” Cool
2.46
2.95 2
2.68
3.03
12” Warm
1.86
1.42 5
2.23
1.66
9” Daylight
2.41
2.21 4
2.00
2.45
9” Cool
2.53 3
2.89
9” Warm ¤
1.11 6
2.36
1.24
¤ Significant gender difference in mean preference score

12. Variables Influencing Light Preference
Effect
Wilks’ Lambda F df
Sig.
CCT
0.72
11.28
2, 57
<.001***
CCT *
Gender
0.85
5.09
.009**
CCT * Brightness
0.77
8.36
.001**
Visual Stimuli
0.61
37.57
1, 58
* p<.05
**p<.01
***p<.001

13. Guttman Analyses Light Preference by Pair Color Trial % White Trial 65
Consistent
Preference
Color Trial %
White Trial
9” Cool over 12” Warm 65 70
9” Cool over 9” Warm 75 67
12” Daylight over 12” Warm
12” Daylight over 9” Daylight 58
12” Daylight over 9” Cool 62
12” Daylight over 9” Warm 63 57
12” Cool over 9” Daylight 53 55
9” Cool over 9” Daylight 50 52

14. Discussion Men broader range of preference
Evaluating under a ‘tighter’ set of rules?
Presence of color panel decreases range of preference
Less ability to differentiate when ‘distracted’?
More indicative of ‘real’ perception?
“Cold” response to Warm lights
Environmental influence?
Differing content of anecdotal comments?

15. Discussion Consistent preference for bright daylight tubes
Environmental/task influence?
Mixed response to brightness
Evidence of a brightness threshold?
Only partial evidence of an overall preference pattern

16. Thank you for your time mtheeman@gc.cuny.edu Please contact me at the
Graduate Center – City University of New York