Investigating the Impact of Daytime Exposure to Blue-Enriched Light and the Power of Expectancy: Modest Benefits to Arousal and Cognition

John Graybeal

Advisor: Patrick E McKnight, PhD, Department of Psychology

Committee Members: Craig McDonald, Tyler Shaw

David J. King Hall, #2073A
December 12, 2016, 11:00 AM to 08:00 AM


Intrinsically photosensitive retinal ganglion cells (ipRGCs) capture information about light which the brain uses to regulate arousal. Due to the sensitivity of ipRGCs to blue light, recent research has become concerned with the potentially adverse effects of nighttime exposure to light sources that contain a high proportion of blue light. Fewer attempts have been made to examine whether daytime exposure to blue-enriched light may be beneficial to both arousal and subsequent cognition. In this study, we compare the effects of blue-enriched light to blue-depleted light. We also examine the role of expectancy by having a subset of participants read a script indicating the lighting in the room should aid their cognitive performance, when in fact they were receiving blue-depleted light. We found evidence that blue-enriched light did improve some aspects of arousal, particularly by increasing heart rate, and that these benefits did lead to modest benefits in cognition. In some cases, the benefits of expectancy on arousal were similar to the effects of blue-enriched light, although these effects did not always translate into benefits on cognitive tasks, and may have even been harmful in some cases, indicating an effect of complacency.