Food label granularity and working memory: effects on food choice in a randomized controlled trial

While prior research on front-of-package labels has focused on their design, the impact of their informational granularity—or level of detail—on consumer choice remains understudied. This study aimed to investigate how the informational granularity of food calorie labels, in conjunction with consumers’ working-memory capacity, influences choice behavior. Methods: A randomized controlled trial was conducted (UK adults, N = 498) in which participants completed a cereal-shopping task after being assigned to one of three conditions: coarse label, detailed label, or no label. Working-memory capacity was evaluated via a three-level n-back test. The primary outcomes measured were the average number of calories per chosen product and the probability of selecting low-calorie options. Multilevel models were employed to test both main and interaction effects, with the Benjamini–Hochberg adjustment applied to control the false discovery rate. Results: Compared with the control condition, food labels reduced mean calorie selection by 4.56%. Each one-unit increase in 3-back performance resulted in an additional 14 kcal reduction under coarse labels and 18 kcal under detailed labels. Individuals with high working memory capacity exhibited a preference for moderate-calorie products over the lowest-calorie products when detailed labels were displayed. The effects of capacity under coarse labels were less pronounced and primarily limited to avoiding the lowest-calorie option. These findings provide conceptual insights into information optimization and offer practical guidance for policymakers on designing effective FOP schemes by specifying when detail helps versus hinders consumer choice.