A prompt plus delayed contingency procedure for reducing bathroom graffiti.

The team wanted to stop graffiti in campus men’s rooms. They taped a small sign above each urinal. The sign said the bathroom is cleaned for you, please keep it clean for others.

Three restrooms were used. Staff counted new marks every day. They started the signs at different times to be sure the sign, not luck, caused the change.

Graffiti stopped the same day the sign went up. No new marks appeared in any of the three rooms. The clean walls lasted the full three-month check.

Choi et al. (2018) did a similar test in the same place. They also used signs, but aimed at hand-washing, not graffiti. Their signs alone helped a little, yet adding a real-time feedback screen helped more. This shows the same cheap prompt can work, but feedback can boost it when the act is harder to see.

Tanoue et al. (1988) cut handicapped-parking violations with new signs plus quick police checks. Both studies got big, fast drops in rule breaking just by changing posted words. The 1988 paper added a brief enforcer, while Critchfield (1996) used only the sign, proving words alone can be enough for some problems.

Okinaka et al. (2011) used prompts plus on-the-spot praise to make riders walk their bikes. Their prompt package needed a live person. Critchfield (1996) shows a sign can work without staff time, a cheaper fix when behavior leaves a visible trace like marker on tile.

You can wipe out small rule breaking with a single polite sign. Pick a short altruistic message, post it where the act happens, and measure for a week. If it works, you have a zero-effort tool that keeps gains for months. If not, add feedback or praise like the later studies. Either way, you start simple and only spend more when you must.