As NASA continues to develop next-generation solid-state lighting technology, medical researchers continue to learn more about the psychological influence of lighting on human decision-making, among other areas of neuroscience.

Scientists have long known that sunny days can brighten one’s mood, while clouds sometimes bring us down. New evidence, however, shows that both positive and negative emotions may be intensified by brighter light, with lower lighting dampening those moods. Investigators from the University of Toronto Scarborough in Canada and Northwestern University reported this week on six studies conducted under varying lighting conditions.

Lighting Affects Mood, Decision-Making Capacity
Lighting intensifies our mood states, affecting our decision-making process. Investigator Alison Xu led the study from the University of Toronto. University of Toronto

What they found surprised them. Although past study had found a correlation between mood states and weather, investigator Alison Jing Xu, an assistant professor at the University of Toronto, says the team asked study participants to rate several qualities, including the spiciness of chicken wing sauce and the aggressiveness of a fictional character, among others.

Xu and her colleagues found that good, sunny weather generally intensified the individual’s emotional state, for good or bad. Sitting in a brightly lit room, study participants professed greater desire for the spicy chicken sauce, and for the attractive person rated in the exercise, too.

"Contrary to [previous] results, we found that on sunny days depression-prone people actually become more depressed," Xu said in a statement, referring to suicide rates peaking during the sunshine of late spring and summer. "Bright light intensifies the initial emotional reaction we have to different kinds of stimulus including products and people," Xu said.

The investigators said the research had implications particularly for the retail sales industry. "If you are selling emotionally expressive products, such as flowers or engagement rings, it would make sense to make the store as bright as possible," Xu said.

Source: Xu, Alison, Incandescent Affect: Turning On The Hot Emotional System With Bright Light. Journal of Consumer Psychology. 2014.