Researchers at the University of Toronto Scarborough report their studies have shown human emotion, whether positive or negative, is felt more intensely under bright light.
They asked study participants to rate a wide range of subjects, and their feelings and emotions about them, under different lighting conditions.
Under bright lights the participants reported feeling their emotions more intensely.
"Bright light intensifies the initial emotional reaction we have to different kinds of stimulus including products and people," Toronto researcher Alison Jing Xu said.
The effect bright light has on our emotional system may be the result of it being perceived as heat, and the perception of heat can trigger our emotions, she said.
"Other evidence shows that on sunny days people are more optimistic about the stock market, report higher well being and are more helpful, while extended exposure to dark, gloomy days can result in seasonal affective disorder," Xu said.
Since the majority of everyday decisions are made under bright light, turning down the light may help someone make more rational decisions or even settle negotiations more easily, she said.