Effect of Lighting Illuminance and Color Temperature on Mental Workload in Office Setting

Bao, Jiayi; Song, Xinbo; Li, Yan; Bai, Yinjie; Zhou, Qianxiang · 2021 · Crossref

DOI: 10.21203/rs.3.rs-436975/v1

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Summary

This study investigates how combinations of lighting illuminance and color temperature influence mental workload in office settings, addressing a gap in literature regarding the interaction between these two lighting parameters. The research was motivated by the increasing time people spend under artificial light and the need to optimize office environments for cognitive performance and comfort. The authors hypothesized that specific combinations of illuminance and color temperature would affect mental workload, potentially through an interaction effect. The experimental design involved twelve postgraduate participants who performed a sustained attention task using an "oddball" paradigm under nine different lighting conditions. These conditions were created by varying color temperature (3000 K, 4000 K, and 6500 K) and illuminance (300 lx, 750 lx, and 1000 lx) in a controlled laboratory office environment. Mental workload was assessed using three metrics: subjective NASA-TLX scores, behavioral performance (response time and accuracy), and physiological data derived from electroencephalogram (EEG) recordings, specifically the P3b event-related potential. The P3b amplitude was used as a key indicator, where higher amplitudes suggest lower mental workload and greater relaxation. Results indicated that while subjective NASA-TLX scores showed no significant main effects for either illuminance or color temperature, physiological and behavioral data revealed significant influences. P3b amplitudes were significantly affected by color temperature (P = 0.009) and illuminance (P = 0.038). Specifically, the highest P3b amplitudes, indicating the lowest mental workload, occurred at a color temperature of 3000 K and an illuminance of 750 lx. Behavioral analysis showed that response times were shortest at 300 lx with 3000 K and at 1000 lx with 6500 K. Notably, no significant interaction between color temperature and illuminance was found in any of the measured outcomes, contradicting the initial hypothesis. The combination of 3000 K and 750 lx was identified as the optimal lighting condition for minimizing mental workload in office environments. The significance of this study lies in providing evidence-based lighting recommendations for office design to enhance cognitive efficiency and reduce mental strain. The finding that 3000 K and 750 lx is optimal suggests that moderate, warm-white lighting is preferable for sustained attention tasks. However, the lack of a significant interaction effect implies that illuminance and color temperature may influence mental workload through independent rather than synergistic mechanisms. The authors note limitations, including the small sample size of healthy students and the potential confounding effect of screen light, suggesting that future research should explore these factors in more diverse populations and controlled screen conditions.

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• roadway lighting effects