Why a 10-per-cent chance of winning coffee changed habits

A free coffee. One in 10 odds. That’s all it took to get people to ditch their disposable cups and embrace reusable ones at bustling university cafés.

A research team from the University of B.C. psychology department and the Institute for Resources, Environment and Sustainability turned an everyday coffee run into a game of chance—and it worked. Reusable cup usage nearly tripled at Blue Chip café and skyrocketed at Loafe café.

The psychology behind it

It wasn’t just about the coffee. According to the researchers, it was the thrill of a possible win that did the heavy lifting. People love the buzz of a “what if.” Psychologists call it the power of anticipation—that little jolt of excitement you feel when there’s a chance to win something, no matter how small. This emotional high makes the effort of remembering a reusable cup seem worth it, and is even more motivating than a guaranteed discount. Add a touch of social proof (other people are doing it too), and you’ve got a winning formula.

Why does this matter?

Every year, 300 billion disposable cups are tossed away, littering landfills and oceans. Unlike taxes or bans, which often spark resistance, this approach taps into something people enjoy: a chance to win. It’s proof that even small tweaks in how we frame rewards can drive big changes in behaviour.

What’s next?

The team behind the study thinks this approach could work for other eco-friendly actions, like reusable packaging. For cafés and businesses, it’s a no-brainer: a low-cost way to save the planet while keeping customers smiling.

Journalists can email erik.rolfsen@ubc.ca to request an interview with the researchers, and read more about the SEEDS Sustainability Program which supported this research.