In a 1969 experiment, famed Stanford psychologist Philip Zimbardo parked a broken-down car in two neighborhoods: one low-income urban, the other middle-class suburban. In the urban neighborhood, where broken windows and graffiti were everywhere, the car was stripped within hours. In the suburbs, the car sat untouched for more than a week until a researcher busted a window himself, after which the vandals set in [source: Kelling and Wilson].
Two criminologists writing in the Atlantic used the "broken windows" theory to suggest a method of reducing crime: Cracking down hard on petty offenses like turnstile-jumping would deter more serious crimes like robbery and murder. Many cities implemented this, most famously New York City under Mayor Rudolph Giuliani. And while the crime rate in New York did decrease, social scientists failed to prove a causal relationship between outward signs of neglect and crime rates [source: Sterbenz]
However, one intriguing 2008 study out of the Netherlands seemed to show a connection. The researchers placed a "no graffiti" sign in front of a wall where people often parked their bikes. Then they attached advertising flyers to the handlebars of the bikes. First, they painted the wall a solid color and counted how many flyers were tossed on the ground. Another day, they sprayed the wall with graffiti and counted the littered flyers. More than twice as many people littered when there was graffiti on the wall [source: Bryner].