Lead researcher Ruiying Cai, an assistant professor in the WSU School of Hospitality Business Management, said U.S. restaurants with more than 20 locations are already required to show the calorie content of food on their menus. By representing these values incongruously — using physically larger numbers on the page when they’re attached to lower-calorie options, and smaller numbers for high-calorie foods — Cai said businesses can successfully “nudge” customers toward healthier choices.

“When restaurants use a larger font size for the calorie content of healthy foods, even though the number itself has a smaller value, it will increase consumers’ preference to order the healthier item,” Cai said.

For the study, recently published in the International Journal of Hospitality Management, participants were asked to choose between a less healthy item like a smoked beef burger and a healthier option like a grilled chicken sandwich. They were then randomly assigned to two groups. In the first group, number values and font size rose and fell together. In the second group, the relationship between the numbers’ magnitude and their size was incongruent, meaning the font size became smaller as the number values rose and vice versa.

Researchers also posed questions to gauge how health-conscious participants were and gave varying time limits to some to measure the effect time constraints have on their decisions. Cai said the study results showed that participants in second group, who saw low calorie counts printed in large fonts, were more likely to lean toward the healthier option. Respondents who indicated they were less health-conscious were also the most affected, particularly when there was a tight timeframe to make the choice.

People who had a high level of health awareness were less likely to be swayed, Cai said, but this is likely because they already favored healthy food.

“Even if you use some of the smart tricks, it does not work as well as for those who are not so knowledgeable about health,” Cai said.

The study leverages a phenomenon called the “numerical Stroop effect,” which uses incongruity to emphasize the lower numbers and slightly slow the decision-making process, to help coax customers toward healthier menu options.

In its classic form, the Stroop effect is described as a delay in reaction time related to stimuli. For example, if the word “purple” is written in green font, it takes respondents longer to call out which color they’re seeing than if the word and the color match. Clinicians use this principle to measure attention capacity and processing speed in patients. Similarly, the numerical Stroop effect is observed when the physical size of the number does not match its actual magnitude — as when the number 50 is in a larger font than the number 80.

Restaurants have an interest in encouraging patrons to make healthier choices, Cai said. However, simply labeling the food as healthy may not have the intended effect.

“Healthy food items could be profitable for restaurants, but whenever a ‘healthy’ label is attached, people may assume it does not taste good,” she said. “We’re trying to provide restaurants with subtle cues, rather than saying it out loud.”

Cai’s coauthors were Laurie Wu and WSU alumna Lu Lu; both are associate professors at Temple University’s Fox School of Business.