This study assessed the effectiveness of posting signs for reducing gr
affiti in three men's restrooms on a college campus using a multiple b
aseline across settings design. During baseline, graffiti increased al
most daily in each of the three settings. Immediately following the in
tervention, no marks were made on ally of the three walls. Results wer
e maintained at 3-month follow-up. A possible explanation for the resu
lts is that the signs specified an altruistic contingency.