Relationship between Concentration of Subjects and the Illuminance Ratio between Ambient Lighting and Task Lighting

Abstract

We compared the concentration of subjects under general illumination, where the ambient illuminance was equal to the task illuminance, with the concentration of subjects under partial illumination, where the ambient illuminance was lower than the task illuminance. The level of concentration of the subjects was evaluated by subjective appraisals, observations of the behavior of the subjects, and measurements of lambda responses (a brain response). The subjective appraisals showed that the subjects found it easiest to concentrate on routine office duties under the general illumination, but they found it easiest to concentrate on more intellectually demanding duties like planning and studying under the partial illumination. Observations of subject behavior and lambda responses measurements clearly showed that the subjects could concentrate better on their work under the partial illumination than they could under the general illumination when they had to do both intellectually demanding duties and just routine office duties. Furthermore, it was confirmed that subjective appraisals, objective evaluations such as observation of subject behavior and measurements of physiological responses are indispensable in evaluating the influence of illumination on the concentration of subjects.