Graffiti on the walls, trash in the street, bicycles chained to a fence, all resulted in a decline in how people behaved in a series of experiments.
A bit of litter or graffiti didn't lead to predatory crime, but actions ranging from littering to trespassing and minor stealing all increased when people saw evidence of others ignoring the rules of good behavior, Dutch researchers report in Thursday's online edition of the journal Science.
In normal behavior most people try to act appropriately to the circumstances, explained lead author Kees Keizer of the faculty of behavioral and social sciences at the University of Groningen, Netherlands. But some tend to avoid effort or seek ways to gain for themselves.
Things like littering an area or applying graffiti change the circumstances by indicating that others are not behaving correctly, which weakens the incentive for people to do the right thing.
So the researchers were not surprised that people littered more in messy area, for example. But, added Keizer: "We were, however, surprised by the size of the effect."
Here's an example:
The researchers found a tidy alley in a shopping area where people parked their bicycles. There was a no-littering sign on the wall.
The researchers attached flyers for a nonexistent store to the bike handlebars and observed behavior.
Under normal circumstances, 33 percent of riders littered the alley with the flyer. But after researchers defaced the alley wall with graffiti, the share of riders who littered with the flyers jumped to 69 percent.
They did a half-dozen similar experiments, all with similar results.
While the study seems to deliver a negative message, Keizer pointed out that "it also shows that municipal officials and the public can have a significant impact on the influence of norms and rules on behavior."
In other words, keep public areas neat and people will be less likely to make a mess.
The work is related to the "Broken Window Theory," which suggests that urban disorder such as broken windows and graffiti encourage petty crime.
This research doesn't go that far, said Robert J. Sampson, chairman of Harvard University's department of sociology.
"It's an interesting study, it's very clever. And the results are believable within the limited bounds set by their design," said Sampson, who was not part of the research team.
But the results don't show that disorder spreads to predatory crime, he said, what they show is that disorder increases people's likelihood of committing (similar) acts."
In addition to the alley with graffiti, here's how the experiments worked:
A fence partly closed off the main entrance to a parking lot. There was a narrow gap and a no-admittance sign that pointed out a new entry, 200 yards away. A second sign prohibited locking bikes to the fence.
When the fence was clear, 27 percent of people heading for their cars ignored the no-admittance sign and squeezed through the gap in the fence. But after several bikes were locked to the fence in defiance of that ban, 82 percent of people going to their cars squeezed through the prohibited entry.
Flyers were placed under the windshield wipers of cars in a parking garage next to a market. A sign on the wall asked people to return their shopping carts to the market.
When the lot was clear of shopping carts, 30 percent of drivers littered the lot with the flyers. But when a few carts were left in a disorderly state around the garage, 58 percent of people littered.
Two weeks before New Year's Day researchers visited a bicycle parking shed near a train station and attached flyers to the handlebars. Under normal conditions 52 percent of the riders littered the shed with the flyers. Then the researchers set off fireworks outside the shed - which residents know is illegal in the period before New Year. Hearing the fireworks, 80 percent of riders littered the shed.
Tests Five and Six:
An envelope with money visible through the address window was placed sticking out of a mailbox.
Under ordinary conditions 13 percent of passers-by stole the envelope.
When the same mailbox was defaced with graffiti the percentage taking the money jumped to 27 percent.
After researchers cleaned the mailbox, but messed up the area around it with litter, 25 percent stole the money.