How expert persuasion impacts willingness to pay for sugar-containing products

Modern consumers face a difficult landscape when they enter a grocery store. Shoppers are surrounded by high-calorie options and sugary treats that are often described as irresistible. This “obesogenic” environment makes it difficult for individuals to maintain healthy diets, despite their best intentions. Health organizations and policymakers have long sought ways to support better decision-making in these settings.

A popular approach in recent years involves the use of “nudges.” These are subtle interventions designed to steer people toward better choices without forbidding the unhealthy ones. Common examples include placing healthier items at eye level or adding nutritional labels to packaging. However, previous research on these tactics has yielded mixed results. Some labels work, while others seem to have little effect on consumer behavior.

A new investigation published in Frontiers in Nutrition in 2022 explores a different type of nudge. The study examines whether a direct, persuasive story told by a health expert can change how much value a consumer places on sugary foods. The researchers designed an experiment to see if listening to a “healthy eating call” would decrease the amount of money people were willing to pay for sugar-containing products.

Psychology of Selling

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Seeking a More Effective Intervention

The study was led by Ioannis Ntoumanis and a team of researchers from the Institute of Cognitive Neuroscience at HSE University in Moscow, along with colleagues from Aalto University in Finland. The team identified a specific gap in the existing literature regarding food choices. Most prior interventions focused on changing the external presentation of food, such as its visibility or packaging labels. Fewer studies have looked at how to change the consumer’s underlying perception of the food itself.

The researchers proposed that a narrative—specifically a first-person account by a credible expert—might be more effective than a simple label. They drew upon the concept of “willingness to pay” (WTP). This is an economic metric that identifies the maximum amount of money an individual is willing to spend to acquire a specific good. By measuring WTP, the team hoped to gauge the actual value consumers assigned to different food products before and after an intervention.

To understand the potential impact of the narrative, the researchers also looked at individual personality traits. They considered the “Need for Cognition,” which measures how much a person enjoys complex thinking. They also assessed the participants’ existing health knowledge. The team hypothesized that people who enjoy thinking deeply might be more engaged by the scientific content of the expert’s message.

Designing the Bidding Experiment

The researchers recruited forty-eight participants for the experiment. The group consisted of young adults with an average age of roughly twenty-five. All participants were healthy and stated that they generally consumed sweets. The team divided these participants into two distinct groups: an experimental group and a control group.

The core of the study involved a computerized bidding task. Participants viewed sixty different pictures of food products. Half of these items were labeled “sugar-free,” and the other half were labeled “sugar-containing.” The products included familiar items like cookies and muffins. To ensure the stakes were real, the researchers gave each participant an endowment of money.

The participants used a slider to indicate their bid for each item. The researchers utilized a method known as the Becker-DeGroot-Marschak auction. In this system, the participant’s bid is compared to a randomly drawn price. If the participant’s bid is higher than the random price, they purchase the item at that random price. This mechanism ensures that participants bid their true value for the product, rather than trying to game the system.

Establishing a Baseline

Before the main intervention, all participants completed a baseline round of bidding. This first block established how much each person was willing to pay for the sugar-free and sugar-containing items before hearing any specific health advice. To control for the general effect of listening to a story, everyone listened to a neutral narrative about photography before this first block.

The data from this initial phase revealed an interesting preference. Participants generally bid higher amounts for the products labeled “sugar-free” than for those labeled “sugar-containing.” They also took slightly longer to make their decisions regarding the sugar-free options. This suggested that the labels alone influenced value perception to some degree, even before the expert intervention occurred.

The Expert Intervention

Between the first and second blocks of bidding, the researchers introduced the experimental manipulation. The experimental group listened to a seven-minute narrative delivered by a nutritionist. This “healthy eating call” was a first-person account that emphasized the health risks associated with sugar consumption. The story combined scientific facts with the narrator’s personal professional opinion.

Simultaneously, the control group listened to a narrative of similar length that was unrelated to food. Their story focused on the topic of handwriting. This ensured that both groups spent the same amount of time listening to a recording, isolating the content of the message as the variable. After listening to their respective recordings, both groups repeated the bidding task for the same sixty food items.

Analyzing the Shift in Value

The researchers analyzed the difference in bids between the first and second blocks. They calculated the “delta,” or change, in willingess to pay for each product type. The analysis compared how the bids changed for the group that heard the nutritionist versus the group that heard the handwriting story.

The results showed a significant interaction between the type of narrative and the type of food. For the participants who listened to the health expert, the willingness to pay for sugar-containing food dropped significantly. The narrative successfully reduced the monetary value these participants assigned to unhealthy options.

In contrast, the expert’s narrative did not increase the value assigned to the sugar-free food. The bids for the healthy options remained largely unchanged. This finding indicated that the intervention worked primarily by devaluing the negative choice rather than by boosting the appeal of the positive choice.

Examining Personality Factors

The team also processed the data regarding personality traits. They looked for patterns connecting the participants’ “Need for Cognition” and health knowledge to their bidding behavior. The researchers had anticipated that those with a high need for cognition would be more influenced by the complex arguments in the expert’s story.

The data did not support this secondary hypothesis. The analysis revealed that the effect of the narrative was consistent across the board. Neither the participants’ intellectual curiosity nor their prior health knowledge acted as a moderator. The reduction in willingness to pay for sugary foods occurred regardless of these individual differences.

Emotional Components of the Narrative

While the main experiment focused on monetary bids, the researchers conducted a separate pilot study to understand the emotional impact of the stories. This side investigation asked a different group of people to rate their feelings after listening to the narratives. The results showed that the nutritionist’s story induced higher levels of fear and sadness compared to the control story.

The researchers suggest that this emotional response may be a mechanism driving the change in value. The feelings of fear or sadness linked to the expert’s description of health risks likely contributed to the lower bids. This aligns with the concept of “negativity bias,” where negative information has a stronger impact on behavior than positive information.

Implications for Business and Marketing

The findings offer practical insights for those in the food industry and public health marketing. The study demonstrates that reducing demand for a product can be achieved through expert persuasion that highlights negative attributes. This suggests that marketing campaigns aiming to curb unhealthy habits might find more success by emphasizing the downsides of the bad choice rather than extolling the virtues of the good choice.

For businesses focused on healthy alternatives, the results imply that simply labeling a product as “sugar-free” does increase value compared to sugary rivals. However, trying to further boost that value with expert testimonials might be less effective than using those testimonials to discourage the consumption of the competitor’s unhealthy product. The consumers in this study were more ready to devalue the “bad” than to overvalue the “good.”

Questions for Future Investigation

This study opens several new avenues for inquiry in the field of consumer behavior. The researchers note that their experiment used a generic “sugar-containing” label. Future research could investigate whether these findings hold true when applied to real-world brands that do not carry explicit warning labels.

The role of the narrator also presents a new question. This study utilized a health expert to deliver the message. It remains to be seen whether a narrative from a peer or an ordinary person would have the same effect. Different audiences might respond differently to authority figures versus relatable social peers.

Finally, the mechanism behind the decision-making process warrants further study. The researchers propose that future experiments could utilize brain imaging technology. Observing neural activity while participants listen to the narrative could reveal how the brain processes expert advice and translates it into a monetary valuation of food. This would help clarify the link between the emotional centers of the brain and the economic decisions made in the checkout line.