A prompt plus delayed contingency procedure for reducing bathroom graffiti.

This study assessed the effectiveness of posting signs for reducing graffiti in three men's restrooms on a college campus using a multiple baseline across settings design. During baseline, graffiti increased almost daily in each of the three settings. Immediately following the intervention, no marks were made on any of the three walls. Results were maintained at 3-month follow-up. A possible explanation for the results is that the signs specified an altruistic contingency.