Keizer said littering jumped because the socially appropriate instinct -- to deposit the flier in a trash can -- was overtaken by the feel-good instinct to let someone else throw it away.
In other experiments, the presence of four shopping carts strewn about a parking lot in violation of posted signs boosted the percentage of people who littered to 58%, from 30%. The sound of illegal fireworks increased the percentage of litterbugs near a busy train station to 80%, from 52%.
To see whether social disorder would induce citizens to steal, Keizer left an envelope containing 5 euros (about $6.26) hanging conspicuously from a mailbox. When the mailbox was clean, 13% of passersby stole the envelope. When the mailbox was surrounded by trash, the percentage jumped to 25%, and when the mailbox was covered in graffiti, it rose to 27%.
"It is quite shocking that the mere presence of litter resulted in a doubling of the number of people stealing," Keizer said.
James Q. Wilson, the political scientist who developed the "broken windows" theory with George L. Kelling, said the Netherlands experiments bolstered his hypothesis.
"If public authorities worry about order, it affects the way people behave," said Wilson, now the Ronald Reagan Professor of Public Policy at Pepperdine University in Malibu.
But Bernard Harcourt, a professor of law and criminology at the University of Chicago who has done studies debunking "broken windows," said Keizer's scenarios were too quaint to take seriously.
"We don't care about those kinds of trivial, manipulated delinquent acts," he said. "What we care about is violence."
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karen.kaplan@latimes.com
