Bridges connect places, people—and underneath them live trolls, slurping, snorting, enviously watching people go by. But where do trolls come from? 

Good (academic) reading in "Anyone Can Become a Troll: Causes of Trolling Behavior in Online Discussions," by Justin Cheng, Michael Bernstein, Cristian Danescu-Niculescu-Mizil, Jure Leskovec.

A predictive model of trolling behavior shows that mood and discussion context together can explain trolling behavior better than an individual’s history of trolling. These results combine to suggest that ordinary people can, under the right circumstances, behave like trolls.

Too often we Americans forget prisons are supposed to be rehabilitative, that the vast majority of prisoners aren't monsters. Whereas, in Dutch-land:

About a third of Dutch prison cells sit empty, according to the Ministry of Justice. Criminologists attribute the situation to a spectacular fall in crime over the past two decades and an approach to law enforcement that prefers rehabilitation to incarceration.

“The Dutch have a deeply ingrained pragmatism when it comes to regulating law and order,” said René van Swaaningen, professor of criminology at Erasmus School of Law in Rotterdam, noting the country’s relatively liberal approach to “soft” drugs and prostitution. “Prisons are very expensive. Unlike the United States, where people tend to focus on the moral arguments for imprisonment, the Netherlands is more focused on what works and what is effective.”