Psychological Science 2017, 40(6) 1328-1334 DOI:     ISSN: 0412-1961 CN: 21-1139/TG

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Keywords
Illuminance
Cognitive performance
Subjective mood
Alertness
Mediating role
Daytime
Authors
ZHU Ying-Ying
YANG Min-Ji
YAO Ying
XIONG Xiao
ZHOU Guo-Fu
PubMed
Article by Zhu,Y.Y
Article by Yang,M.J
Article by Yao,y
Article by Xiong,x
Article by Zhou,G.F

Effects of Indoor Illuminance on Cognitive Performance: The Mediating Role of Subjective Mood and Alertness

Abstract

The aim of the present study was to investigate the effect of indoor Illuminance on healthy adults’ cognitive performance, subjective mood and alertness during daytime office hours. In addition, this study also examined whether the relationship between daytime light exposure and cognitive performance is mediated by subjective mood and alertness in healthy adults. A single factor between-subject design with Illuminance at eye level (300 lx vs 1200 lx) as the independent variable was employed in the current study. A total of 106 participants took part in the formal experiment according to some strict selection criteria, such as chronotype, medical and sleep disorders, general health, life habits, affective disorders, smoking, drug consumption, body mass index, shift work and transmeridian flights during last 2 months. Based on previous findings, the present study hypothesized that exposure to bright light would promote task performance compared to the dim light, and bright light would have a beneficial effect on positive mood and subjective alertness. In addition, it was also hypothesized that subjective alertness mediates the relationship between bright light exposure and three indicators of cognitive performance: working memory, long-term memory and inhibitory capacity; positive mood mediates the relationship between bright light exposure and three indicators of cognitive performance of working memory, long-term memory and inhibitory capacity. Results showed that participants responded faster on Go/No go and 2-Back task under bright light exposure compared to the dim light exposure, while there was no significant difference on accuracy of these two tasks; in contrast, no significant effect of indoor Illuminance on Long-term memory task was observed in the current research. Subjective alertness and positive mood were also significantly improved in the high illuminance (1200 lx) in comparison with the low illuminance condition(200 lx). Correlation analyses among Illuminance levels, positive mood, negative mood, subjective alertness and task performance (Go/No go, 2-Back) revealed that there were positive correlations between Illuminace level and positive mood, subjective alertness and Go/No go task; negative correlations between Illuminance level and subjective alertness, Illuminance level and Go/No go task, Illuminance level and 2-Back task, positive mood and subjective alertness. The multivariate stepwise regression analysis indicated that Illuminance and subjective alertness were significant factors in predicting Go/No go performance, and also Illuminance and positive mood were significant factors in predicting subjective alertness. Based on correlation and multivariate stepwise regression analysis, a relational model was established and results showed that the effect of indoor Illuminance during daytime on Go/No go task was fully mediated by subjective alertness, and the relationship between Illuminance and subjective alertness was partially mediated by positive mood. It should be noted, however, that no mediating effect for negative mood was found in both the relationships between Illuminance and cognitive tasks, the subjective alertness and indoor Illuminance. These findings suggest that even during daytime office hours, bright light exposure did have a beneficial effect on task performance, positive mood and subjective alertness. Additionally, subjective alertness was a key variable in the effect of indoor Illuminance during daytime on cognitive functions, especially for the attention-related performance.

Keywords Illuminance   Cognitive performance   Subjective mood   Alertness   Mediating role   Daytime  
Received 2016-07-14 Revised 2017-09-03 Online: 2017-11-20 
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Email: zhougf@scnu.edu.cn
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