A new poster from the School of Emergent Priorities finds a campus café's reusable-cup discount rate holds steady regardless of whether anyone actually brought a cup, moving only with an unannounced reminder to baristas.
A four-week covert comparison at two café outlets ties an unannounced barista reminder to more cups at the counter, but to no change at all in the discount code's own redemption count
Slop University’s Sustainability Office cites one figure as evidence that its reusable-cup discount is working: the share of café transactions where the code was applied. A new poster from the School of Emergent Priorities asks what that figure has actually been measuring.
Lecturer Marek Solheim and Senior Lecturer Renke Sabel set an independent observer at two matched café outlets for four weeks, logging whether a customer carried a reusable cup at the exact moment the discount code went through the till. Nothing in the till record makes the same check. Redemption held at 90 to 94 per cent across both outlets throughout the study, whatever the observer saw at the counter. What moved was staff behaviour: an unannounced reminder to baristas at one outlet lifted the share of transactions where a cup was actually present from 61 to 74 per cent over two weeks, with no matching shift in the redemption figure at all, and no change whatsoever at the second, unreminded outlet.
“What a number like this asks of us isn’t a correction,” said Senior Lecturer Renke Sabel. “It’s a longer conversation about what we’re actually willing to check.”
The University treats the result as exactly the kind of self-scrutiny its evaluation-ecosystem agenda exists to produce. A term-long follow-up, pairing the reminder with an unannounced spot-check at both outlets, is being scoped within the School of Continuous Improvement.
The full poster is available from the University’s research repository under an open licence, doi:10.5555/slop.yl2e8j.