Can different colour temperatures in light sources influence human performance and psychoemotional state? The possibility that it might is down to the fact that light can trigger photoreceptor cells responsible for regulating circadian (diurnal) rhythms in the human body. To test the effects of different colour temperatures of LED luminaires on the human body, a study has been conducted by Kazan State Power Engineering University and Lighting Technologies.
The University’s department of lighting fixtures and medical electronics (LME) undertook studies from 27 April – 28 May 2015. Two neighbouring classrooms of an identical size and interior design, where both lectures and laboratory work took place, were allocated for this study at the university (see diagram).
Classroom plans with LED-based and fluorescent luminaires
The first classroom (A-212) had its entire lighting system replaced with Color Fusion series luminaires by Lighting Technologies, namely the LINER/S LED 1200 CF model with adjustable colour temperature, and a lighting control system (controller and control panel) with pre-programmed lighting scenarios. In the second classroom (A-214), the lighting system was left as is, consisting of standard neutral-coloured linear fluorescent luminaires without lighting controls.
The comparative assessment of the effect of colour temperature on the human body was conducted in compliance with the regulatory requirements for lighting at educational institutions and with an identical luminaire light distribution and intensity in both cases. Indicators of performance, well-being and mood were measured during classes in both classrooms. The indicators were measured at colour temperatures of 2800K, 4000K and 5800K in the classroom with LED lighting and at neutral colour temperatures in the classroom with fluorescent lighting.
More than 100 people participated in the study, including male and female students, from the first to fifth year, aged 17 to 23. The total number of processed forms was 239. The research team consisted of teaching staff members from the LME department, a practising psychologist and engineers from Lighting Technologies.
Form-based tests were performed in both classrooms at different colour temperatures of the main lighting. In the correction task, visual performance was assessed by examining the number of characters in the reviewed part of the correction table, productivity, error rate and the accuracy of visual task performance in a specified time frame.
The tapping test is used to determine the state of the nervous system in humans using psychomotor measures. Here, the relative number of dots made on paper in a specified time interval is measured. The well-being, activity, and mood inventory is a form-based test used to assess human psychoemotional state. The idea is that the subjects relate their own state to a number of attributes on a multi-level scale.
The results were evaluated using comparative analysis and statistical data analysis methods such as averaging, significance testing of sample mean differences using Student’s t-test and confidence interval estimation.
Despite the short duration of the study, preliminary conclusions can already be made regarding the effect of colour temperature of lighting on the human body. The influence of different lighting types on visual performance was demonstrated in the study. For example, a 20% improvement in performance in the speed of task completed was observed during tests at a colour temperature of 5800K in comparison to fluorescent lighting. The number of errors was also reduced.
The influence of different lighting conditions on the psychophysiological background was also observed, including a relaxing trend with LED lighting at 2800K. In addition to the form-based tests, the students gave their subjective assessments of the different lighting types. When asked: “How do you feel right now?” at a warm (about 2800K) colour temperature of the lighting, most students reported being relaxed, drowsy and unwilling to perform any activity. In response to the same question at a cold (about 5800K) colour temperature of the lighting, most students reported being alert, energetic and willing to work. To prevent groupthink, the answers were given anonymously, in writing, with silence observed in the classroom.
The research on the visual and non-visual effects of quantity and chromaticity of light on the human organism paves the way for a new era of biologically and emotionally efficient lighting in various applications. Because of the importance of the research, it was decided to carry out a second phase of this work that will commence at the beginning of the new academic period and run through to the end of the year.
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