The mere presence of graffiti and trash encourages people to trash the neighborhood by littering, trespassing or even stealing, a new study has found.
They do so because they feel rules have broken down, the Dutch research has found.
Litter, abandoned shopping carts and impromptu fireworks can all prompt petty crime and feed further social disarray.
The finding confirms experimentally that disorder and disobedience grow in neighbourhoods where rules are openly flouted, a phenomenon dubbed "broken window" theory.
"Broken window theory says that if there are broken windows in houses, it will lead to more disorder and a degrading neighbourhood," says Keizer.
Keizer and colleagues Siegwart Lindenberg and Linda Steg set up six practical experiments to put the theory dating from 1982 to test.
Setting up real-life situations in Groningen in each of the experiments, the researchers tempted random citizens to do something unruly, illegal, or antisocial.
hen, they discreetly watched what happened, without the passers-by realising they were under observation.
In the most striking experiment, Keizer left a 5-euro note protruding from a fully addressed envelope that itself was poking out of a mailbox. The team discovered that people were less likely to steal the money if there was no graffiti or litter on or around the mailbox.
With no litter or graffiti, 13percent of the passers-by stole the money. Thefts doubled to 27 percent when the mailbox was daubed with graffiti, or to 25 percent when it was surrounded by litter.
"It's quite shocking that the mere presence of litter doubled the number of people stealing," says Keizer.
The researchers conclude that one type of antisocial behaviour leads to others, because people's sense of social obligation to others is eroded.
"When people think they can get away with it because other people already have, they do," says Keizer.
The study has been published in the journal Science.