When it comes to being messy, it’s monkey see, monkey do

? Does a messy neighborhood make a difference on how people act? It sure does!

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 a 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 fliers for a nonexistent store to the bike handlebars and observed behavior.

Under normal circumstances, 33 percent of riders littered the alley with the flier. But after researchers defaced the alley wall with graffiti, the share of riders who littered with the fliers 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.