A simple test of full-spectrum light found that changing the lamps in a restaurant's dining room had no noticeable effect on diners' purchases or the length of time at table. The study was motivated by the common perception that full-spectrum light increases people's sense of well-being, which should, in turn, result in behavioral changes. With the cooperation of a table-service restaurant that has two similar dining rooms, the study involved changing the lights in one of those dining rooms. With the lamps replaced, the researchers compared average checks and meal durations between the dining rooms, and also compared the main dining room sales when it had regular incandescent light with sales during the full-spectrum light test. None of the comparisons showed any difference between the regular lighting and the full-spectrum lighting with regard to customers' purchases. Because the change to full-spectrum light in this study was intentionally subtle to conform to the operator's needs, future research should involve a more controlled study that also manipulates and takes into account changes in the brightness of the light. However, the results of this study do not support claims that full-spectrum light affects diners' activities.
Robson, S. K. A., & Kimes, S. E. (2007). Examining the effects of full-spectrum lighting in a restaurant [Electronic article]. Cornell Hospitality Report, 7(12), 6-15.