Stimulus range bias explains the outcome of preferred-illuminance adjustments

Sa Fotios,C Cheal

doi:10.1177/1477153509356018

Abstract

Review of previous studies suggests that mean preferred illuminances determined using an adjustment task tend to lie in the middle of the range of illuminances available, a stimulus range bias. This hypothesis was validated through the results of an experimental study. It is therefore suggested that the adjustment task is not an appropriate method for determining optimum illuminances.

Highlights

Guides for interior lighting often suggest an average horizontal working plane illuminance in the region of 500 lux for spaces such as offices.[1]
An alternative explanation for the results of preferred illuminance adjustment tasks is proposed: the preferred illuminance is significantly influenced by the range of illuminances available to the observer, and studies with different stimulus ranges will lead to different estimates of preferred illuminance
The mean preferred illuminances approached the middle of the range and the higher the upper limit of the stimulus range, the higher the mean preferred illuminance

Summary

Introduction

Guides for interior lighting often suggest an average horizontal working plane illuminance in the region of 500 lux for spaces such as offices.[1] Previous studies have used an adjustment task to investigate the ‘preferred’ or ‘optimum’ illuminance for workplace environments. In this task, the test participant is instructed to vary the illuminance in a space using a dimming control device to set the illuminance to their preferred level. An alternative explanation for the results of preferred illuminance adjustment tasks is proposed: the preferred illuminance is significantly influenced by the range of illuminances available to the observer (the stimulus range), and studies with different stimulus ranges will lead to different estimates of preferred illuminance

Methods

Results

Conclusion