In their field experiments Keizer and his colleagues tested to what extent various subtle signs of disorder in an environment could influence the proliferation of other undesirable behaviors. In one study the researchers found the perfect setting for their test: an alleyway near a Dutch shopping mall where shoppers typically parked their bikes. While the shoppers were at the mall, the researchers affixed one of the store’s advertisements on the handlebar of each bicycle with an elastic band. In one condition, the researchers left the alleyway just as they found it; in a second condition, they added graffiti to the alleyway. Because there were no garbage bins in the area, shoppers returning from the mall to find a printed advertisement attached to the handlebars of their bicycle had a simple choice. Do they remove the advertisement and take it home with them—or do they instead drop it on the ground?
The results revealed that 33 percent of the bicycle owners littered the paper when there was no graffiti to be seen in the alleyway. However, 69 percent did so when graffiti was present.