"Expert persuasion" can decrease willingness to pay for sugar-containing food

Abstract

Recent studies have revealed types of eating nudges that can steer consumers toward choosing healthier options. However, most of the previously studied interventions target individual decisions and are not directed to changing consumers' underlying perception of unhealthy food. Here, we investigate how a healthy eating call-first-person narrative by a health expert-affects individuals' willingness to pay (WTP) for sugar-free and sugar-containing food products. Participants performed two blocks of a bidding task, in which they had to bid on sweets labeled either as "sugar- free" or as "sugar-containing." In-between the two blocks, half of the participants listened to a narrative by a dietary specialist emphasizing the health risks of sugar consumption, whereas the remaining participants listened to a control narrative irrelevant to food choices. We demonstrate that the health expert's narrative decreased individuals' WTP for sugar-containing food, but did not modulate their WTP for sugar- free food. Overall, our findings confirm that consumers may conform to healthy eating calls by rather devaluating unhealthy food products than by increasing the value of healthy ones. This paves the way for an avenue of innovative marketing strategies to support individuals in their food choices.

Keywords: diet and health knowledge; expert persuasion; food choices; healthy eating; narratives; need for cognition; sugar; willingness to pay.

FIGURE 1

Bidding task. Sample trial with food labeled as sugar-containing (A) and sample trial with food labeled as sugar-free (B). At the beginning of each trial, a product was displayed for 4 s. Next, a message was displayed at the top of the screen “How much does this product worth to you?” as in (66). Participants had 5 s to indicate their WTP for this product, using a discrete slider (0–150 MU, with an increment of 10 MU). Last, a fixation cross was shown (2–6 s) and the next trial began.

FIGURE 2

Schematic representation of the experimental procedure.

FIGURE 3

Delta of WTP by group and condition. Due to the problem of p-values associated with large samples (70), we first averaged the data of each participant and only then applied pairwise t-tests, in order to limit the probability of Type I error. Error bars denote mean ± standard error (SEM), after averaging within each participant. The delta of WTP for sugar-containing products was significantly lower for the experimental group as compared to the control group (t = 4.210, Bonferroni corrected p = 0.0003, Cohen’s d = 1.210), but the delta of WTP for sugar-free products was not statistically different between the two groups (t = 1.070, Bonferroni corrected p = 0.578, Cohen’s d = 0.309). It is worth mentioning that the interaction between Group and Condition on the delta of WTP was also found significant in these averaged data, as assessed by a two-way mixed ANOVA [F (1,46) = 5.15, p = 0.028], in line with the significant interaction detected by Model 1. ***p < 0.001.