Evaluating dynamic norm messages and alternative interventions to reduce meat consumption in cafeterias

To meet UK Net-Zero emissions targets, meat consumption must decrease. We present results from two studies evaluating interventions to reduce purchasing of meat-containing meals across university cafeterias in Oxford, UK. Study 1 tested whether two dynamic descriptive norm messages changed meal purchasing. Over eight weeks, four cafeterias displayed a norm message incorporating a socially ‘close’ referent group and three cafeterias displayed a message incorporating a socially ‘distant’ referent group. Two cafeterias were assigned a no-message control condition. A generalised linear mixed effect model suggested both messages decreased odds of cafeteria diners purchasing vegetarian meals, in comparison to control, 'Close' Message: Ratio of Odds Ratios (ORs)=0.79, 95% 95% CI [0.72, 0.86]; 'Remote' Message: Ratio of ORs=0.84, 95% CI [0.76,0.92]. Study 2 involved three pre-post experiments testing whether different interventions changed meal purchasing: re-positioning vegetarian products, increasing vegetarian availability, and introducing vegetarian defaults. Generalised linear models suggested each intervention was associated with significant increases in odds of diners purchasing vegetarian meals, Positioning: OR=1.33, 95% CI [1.24,1.44]; Availability: OR=1.60, 95% CI [1.45, 1.75]; Defaults: OR=1.77, 95% CI [1.61, 1.95]. These study results could be due to norm messaging being less effective at promoting vegetarian meals than interventions in availability, defaults, and positioning. But, given the study designs, they could instead be due to self-selection effects, or regression to the mean.