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Bright light can affect our judgment, study finds

Bright light can affect our judgment, study finds
In one experiment, turning up the lights made people respond more intensely to both positive and negative (but not neutral) words.

Do you have any important decisions to make today? If so, you may want to stay indoors and dim the lights.

For, according to new research, bright light intensifies our emotions — the negative as well as the positive ones — and, thus, influences our judgments.

What’s more, we are mostly in the dark (so to speak) about light’s effect on our decision-making.

The perception of bright light creates “an illusionary experience of heat,” write the two professors of marketing who co-authored the study, Alison Jing Xu of the University of Toronto and Aparna Labroo of Northwestern University. “This psychological experience of heat turns on the hot emotional system, intensifying a person’s emotional reactions to any stimulus. Thus, in bright light, good feels better and bad feels worse.”

A series of experiments

For the study, which was published this month in the Journal of Consumer Psychology, Xu and Labroo conducted several separate experiments in which volunteers were asked to rate a wide variety of things under either bright or dimmed lighting conditions.

The experiments revealed that bright lighting increased people’s sense of warmth, even when the temperature was kept constant. They also found that it made the volunteers more desirous of spicy foods and more likely to consume a “favorable” juice (orange).

But interestingly, the bright lighting also intensified the volunteers’ negative response to an “unfavorable” juice (tomato), and thus decreased their desire to drink it.

In another experiment, turning up the lights made people respond more intensely to both positive and negative (but not neutral) words. It also made the study’s volunteers give more polarized opinions about fictional characters that were presented to them as part of an ad campaign. When the lighting was bright, the volunteers were more likely to say a man in the ad was acting aggressively — and that women in the ad were more attractive.

Builds on previous research

As background information in the study points out, other research has shown that on sunny days people tend to be more optimistic about the stock market and more likely to help others. They also tend to report a greater sense of well-being.

This new study, however, suggests that sunlight can intensify negative as well as positive emotions.

That may help explain, say the authors, why on sunny days people who are prone to depression often become more depressed. For although there is a type of depression — seasonal affective disorder — that is associated with winter and its shorter hours of sunshine, studies have shown that suicides actually peak in the sun-abundant days of late spring and early summer.

But Xu and Labroo’s research also suggests that lighting impacts not just our mood, but our judgment — and without us really being aware of it.

“A majority of everyday decisions are made under bright light, and as a result are likely to be impacted emotionally in this manner,” the authors conclude. “The emotional bias is likely to be stronger on bright days, around noon, when the sun is brightest, and in geographic regions with sunnier rather than cloudier days.”

“From a policy perspective,” they add, “these findings suggest a simple way to nudge people into being less emotional — by simply turning the lights down. On the other hand, for those wanting to sway opinions with passionate claims, or those desiring swift action to overcome procrastination, turning on the lights may be best.”

The study itself is behind a paywall, but you can read a long layperson abstract about the research on the Journal of Consumer Psychology’s website.

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