Would you like some coffee with your sugar? A natural field experiment on the efficiency and acceptability of setting zero sugars as a default in coffee-vending machines

Overview & Synopsis

This paper aims to replicate the effect of a nudge on behavior (efficiency) and acceptability in a natural field experiment. The nudge in our study consists in setting zero sugars as the default level of sugar in hot drinks–vending machines in a French university. We compared Campus A (default option set to 0 sugars) to Campus B (default option set to 3 sugars). We measured the efficiency of this default option by observing the level of sugar actually chosen by the participants, and we measured acceptability through a questionnaire. We hypothesized a high level of efficiency for the nudge and a higher acceptability in Campus A (default option set to 0 sugars) compared to Campus B (default option set to 3 sugars). Our results show that participants with the default option set to zero sugars (Campus A) consumed less sugar than those with the default option set to 3 sugars (Campus B). We also found a high level of acceptability on both campuses, though with no difference between Campus A (where the nudge was implemented) and Campus B (where a future nudge would be implemented). The discussion addresses the applied perspectives and ethical implications of these results.