When are “Dish of the Day” nudges most effective to increase vegetable selection?

Previous research has suggested that featuring vegetable-rich dishes as “Dish of the day” (DoD) could be an operationally feasible and straightforward strategy to promote healthier food choices in restaurants. However, the available evidence regarding the effect of DoD on food choices is limited, and little is known about the conditions of its effectiveness in the field. This study investigates the effect of introducing DoD options in a real self-service restaurant setting on the selection of vegetable-rich options. The objectives are to (1) replicate and measure the DoD effect in this situation; and (2) investigate the moderating role of two features of the choice set: (i) the type of option set as DoD and (ii) the number of alternatives options to choose from. In a living lab experiment, 294 consumers came for lunch to a self-service restaurant and chose between a target vegetable-based dish (vg1) and respectively one, or two, alternatives: a meat-based dish (nvg) and another vegetable dish (vg2). Five choice task conditions were tested, in a between-subjects design: three conditions examined dish choices when two options were available (vg1 versus nvg): no DoD (T1-0); vg1 as DoD (T1a); or nvg as DoD (T1b). Two further conditions used three options (vg1 versus nvg versus vg2): no nudge (T2-0), or vg1 as DoD (T2a). In neutral conditions T1-0 and T2-0 respectively, 34.4% and 23.3% of consumers chose vg1. The DoD effect was observed in all conditions: choices in favour of vg1 increased by 25.2% when in was DoD by 25.2% in T1a vs. T1-0 and by 30% in T2a vs T2-0; while 7.6% more consumers chose nvg in T1b vs T1-0. Regarding the conditions of DoD effectiveness, the size of the DoD effect was larger for the initially less popular dish vg1 (T1a) compared with nvg (T1b). Introducing more options also increased the relative effect of DoD in favour of vg1, from 73% (T1a) to 129% (T2a). There were no effects of the condition on consumer satisfaction with the dish chosen, nor on the amount of food wasted. This research gives insight into the elements of the choice task to consider when setting up nudges, and could help choice architect to better design efficient and acceptable nudges in foodservice settings