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

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

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?

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.

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

Research Roots

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

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?

Methodology 21 light combinations Two trials per participant Familiar room in building 60 office-based employees 38 male - 22 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

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

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

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

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

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?

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

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