Experimental studies on revealing the relationships between luminous environment characteristics and cognitive, ocular and psychological changes

This dissertation proposes a holistic, multi-dimensional approach for analysing task performance by understanding the psychological, physiological and cognitive performance-based changes with respect to various lighting quality factors. The main objective was to observe and integrate these three categories of potential affecting variables into the evaluation of overall task performance of video display terminal (VDT) users. In the existing literature, specifically in daylit offices, human behaviour and physiology are not sufficiently considered while evaluating task performance, or vice versa, performance changes in VDT users are not often taken into consideration while behavioural and psychological processes are analysed. This PhD dissertation describes different stages of conception of this holistic method that includes objective performance measures coupled with ocular and behavioural responses, in order to overcome the limitations associated with the subjectivity and individuality aspects of lighting effects for analysing occupants’ task performance. The assessments were done in a series of experiments in a mock-up office setting under different (day)lighting conditions where participants’ ocular behaviour as well as their subjective assessments were recorded while monitoring photometric quantities including vertical illuminance at the eye and luminance data. In the first experimental phase, an initial study was made for proper integration of the adopted methods and techniques regarding ocular behaviour into visual comfort assessments. Development of several algorithms and tools to identify and translate the ocular behaviour in order to derive the actual luminous distribution perceived by the participants were needed to achieve this goal. In the next comprehensive experimental phase, the impact of daylight illuminance and luminance on various physiological, performance and psychological measures during visual display terminal work was explored. Additionally, the results from the relationships between photometric variables and physiological and subjective responses as well as performance measures are presented. The developed approach demonstrates the need to integrate ocular patterns and human behaviour into task performance assessments, which move us beyond the existing rigid and rough design approaches towards a holistic, human-centric lighting design in computerized offices.