Effects of indoor lighting (illuminance and spectral distribution) on the performance of cognitive tasks and interpersonal behaviors: The potential mediating role of positive affect

Three studies examined the effects of key aspects of indoor lighting (illuminance, spectral distribution) on the performance of tasks that did not primarily involve visual processing. It was hypothesized that lighting conditions which generated positive affect among subjects would influence behavior and cognition in ways consistent with the findings of previous research on the influence of such affect. Results of all three studies offered partial support for this hypothesis. In Study 1, male and female subjects exposed to relatively low levels of illuminance (150 lux) assigned higher performance appraisals to a fictitious employee and included a broader range of words in specific word categories than subjects exposed to relatively high levels of illuminance (1500 lux). In Study 2, subjects exposed to warm white light reported stronger preferences for resolving interpersonal conflicts through collaboration and weaker preferences for resolving conflicts through avoidance than subjects exposed to cool-white light. Additionally, illuminance and spectral distribution (color) interacted to influence subjects' self-set goals on a clerical coding task. In Study 3, receipt of a small, unexpected gift and exposure to warm-white light both increased the amount of time subjects were willing to donate as unpaid volunteers. In addition, in the absence of a gift, subjects volunteered more time under low than under high illuminance.This research was supported by funds from the Niagaru Mohawk Energy-Efficient Seed Research program and from the New York State Energy Research and Development Authority. Study 1 was conducted by Susan G. Daniels in partial fulfillment of requirements for the Master of Science degree. The authors wish to express their sincere appreciation to Marna Bronfen and Jill Thomley for their aid in collection of the data for Studies 2 and 3 and in statistical analyses. Thanks are also due to Sylvania, Inc., for supplying lamps, and to Bob Davis and Peter Boyce for their invaluable assistance in several respects.