Does dimming the lights encourage customers to spend more?

By Emily Ayshford 

Diners hoping not to overindulge during a night out might strategize how to set themselves up for success. Perhaps they look at menus ahead of time or steer clear of that café whose cheesecake they just can’t resist. But there is another factor they probably aren’t considering: the restaurant’s lighting.

New research from the Kellogg School suggests they should be. Lighting, the research found, can change how likely we are to make pleasurable versus practical decisions. And the mechanism at work is not simply that we can see our salad or sundae better in the bright light, and are shamed into healthy choices.

Rather, we feel less connected to others in the dark. So we assign less weight to what others think and more weight to what we authentically desire. And what we desire is cheesecake.

“Ambient light is a very important experience that is easily manipulated,” says Ping Dong, assistant professor of marketing at Kellogg. “This shows a new psychological consequence of darkness—consumers more often choose the option that provides immediate pleasure.”

Lighting can shape behaviors in numerous measurable ways—and marketers have taken note.

The findings also point more generally to the power of light to impact our behavior, which is being researched across disciplines.

“Light is so ubiquitous,” says Dorothy Sit, associate professor of psychiatry and behavioral sciences at Northwestern’s Feinberg School of Medicine, who has studied using light to treat depression. “There’s so much research that needs to be done to understand how light can be used to optimize how people feel at work and at home.”

Feeling Disconnected in the Dark

Lighting can shape behaviors in numerous measurable ways—and marketers have taken note. Previous studies have shown that in darker retail shops, for example, consumers shop at a slower pace. In dimly lit restaurants, consumers underestimate portion size and perceive spicy foods as less enjoyable.

Previous research has also shown that because ambient darkness reduces people’s visual acuity, it makes consumers feel more hidden from others. Researchers had previously proposed that it was this feeling of anonymity that accounts for consumers making more hedonic choices in darkness.

But the Kellogg researchers had another idea.

Dong and Kellogg marketing professor Aparna Labroo knew from other research that when we feel psychologically distant from others, we tend to let our guard down and act truer to our own desires. Perhaps consumers are also more likely to make pleasurable choices in darker settings—reaching for a candy bar instead of an apple, or buying trendy high heels instead of practical flats—not because they feel physically hidden, but because that feeling of psychological distance frees them to do what they really want.

How Lighting Affects Our Choices

To test this hypothesis, the researchers conducted three studies. In each, they manipulated the light levels to see how participants’ choices changed when offered a utilitarian product versus a more enjoyable—or “hedonic”—one.

In the first study, 103 undergraduate students were brought to a room one at a time and asked to imagine they were purchasing a chair. They were presented with two similarly priced options: a utilitarian chair with more back support or a hedonic chair that was more stylish but had only modest back support. For some of the students, the room was brightly lit; for others the lighting was dim. Additionally, some students were told the chair would be used in a public context like an office, while others were told it would be used in a private context, such as their home.

Participants in the dimly lit room preferred the hedonic chair more often than those in the brightly lit room did, regardless of whether they thought the chair would be used in a public or private setting.

“It shows the effect of darkness on hedonic choice,” Dong says. “Even if there are very few people visiting your home, you still prefer the chair with the hedonic benefits if you make the choice in the dark.”

The Psychological Effects of Darkness

In the second study, the researchers asked 180 online participants to make a series of choices, each with a hedonic and utilitarian option. Would they select a competent job candidate or a fun candidate? A mobile app for work or an app for entertainment? A durable laptop or a stylish one? How about a documentary TV program or a romantic drama?

Half of the participants were asked to turn on all the lights in their room before taking the test, while the rest were instructed to turn them off and use only natural light. After they finished the questionnaire, participants responded to statements designed to measure their self-authenticity, such as, “I feel that nobody can tell me what to do” and “I feel I can be myself in my daily situations,” on a scale from 1-9.

How marketers might use these results depends on their goals.

Again, researchers found that those who took the test in a dark room were more likely to choose the hedonic options, compared to those who took the test in a bright room. But, importantly, they also found that participants in dark rooms expressed greater self-authenticity.

“This began to show us a new psychological consequence of darkness,” Dong says.

The finding spurred a new question: Could the tendency be reversed?

In the final study, 350 online participants went through the same process as in the previous study. But this time, before they answered the questions, some participants were asked to list three names of people close to them and a personal experience they had with each one. Other participants were asked to list three of their own facial features.

The researchers found that the majority of those who took the test in the dark again chose the hedonic options, with one big exception: those who had listed their personal connections veered toward utilitarian choices, even though they were in a darker space.

“When we reminded people of their social connections with others, they didn’t feel disconnected in the dark anymore,” Dong says. “It reduced their tendency to act in a hedonic way.”

Lighting and Consumer Behavior

How marketers might use these results depends on their goals. Perhaps restaurants selling healthy food should increase the brightness of the light, Dong says, since healthy food is considered more utilitarian.

“But for restaurants selling cheesecakes and other desserts—more indulgent food—it might be beneficial for them to dim the lights,” she says.

Because lighting is so easy to manipulate, marketers could also change the light from room to room in a store, or change the lighting in specific product ads, cranking up the spotlight on a quinoa salad but dimming the wattage on eclairs.

On the other hand, consumers armed with this knowledge could use it to make better choices, even when lighting cues them to act otherwise.

“Movie theaters are quite dark, and often we order a lot of food,” Dong says. “We could be more mindful of how many calories we order.”

Ditto for the workplace. To get utilitarian work done, keep it bright. And as more and more of us are bringing work home and working late into the night, be mindful of what darkness means for our choices—whether it’s opening that browser tab to do some online shopping, or reaching for a bag of cookies as you type.

Bright Light and Depression

This research is part of a broader line of inquiry that addresses how lighting can impact a range of human behaviors. The findings are influencing fields as disparate as worker productivity, traffic safety, and public health.

In the realm of medicine, doctors have long used bright light to treat patients with seasonal affective disorder in the dark winter months. At Feinberg, Dorothy Sit recently tested whether the therapy could be used to treat patients with a different psychological condition: depression due to bipolar disorder.

In Sit’s study, 46 patients were randomly assigned to receive treatment with either a bright white light or a dim red placebo light. Patients sat in front of their assigned light every day between noon and 2:30 p.m. for 15 minutes at first, gradually increasing their time to 60 minutes per day.

By week six, nearly 70 percent of those using the bright white light reported a remission in their depression, compared with 22 percent of the placebo group.

“The results were quite compelling,” Sit says. “Patients experienced not just mood improvement but functional improvement. They were able to go back to school, back to work, and the side effects were low.”

Do these results mean everyone would benefit from a walk outside after lunch?

“That’s a nice idea,” Sit says, though she can’t yet extend her results beyond those with bipolar disorder. She hopes to conduct further studies to understand the biology and neuroscience behind light therapy.

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This article was previously published in Kellogg Insight. It’s been reprinted with permission of the Kellogg School of Management.

Emily Ayshford is a freelance writer in Chicago.