Malcolm Gladwell—always thought-provoking—recently reviewed the new book Unforgiving Places in The New Yorker (9 June), which examines strategies to prevent violent crime. The book’s author, Jens Ludwig, directs the University of Chicago Crime Lab.

Ludwig’s approach divides the phenomenon of gun violence into two main types, each of which has different motivations and modes of prevention. He believes the reason many preventive strategies fail (or fail to explain changes in homicide rates), is that what works for one type of violence doesn’t work for the other.

In general, people vacillate between two major modes of thinking. One is fast, automatic, and intuitive. It’s why Tony shot Maria’s brother Bernardo in West Side Story. Road rage is another example. This quick, unthinking response is what psychologist Daniel Kahneman calls “System 1 thinking.” By contrast, “System 2 thinking” involves deliberation and careful planning in order to gain something—“cash or phone or watch or drug turf.” Often, revenge. And, again in West Side Story, it’s why Chino shoots Tony. The violence associated with System 2 thinking is a means to an end.

Unforgiving Places points out our criminal-justice system has been designed to counter planned and deliberate System 2 crimes, when the real problem is those spontaneous, reactive ones, the homicides that occur in a moment of irrationality. According to FBI data, they account for more than three-fourths of murders committed over the past twenty years. The Chicago Police Department estimates that argumentsare at the root of between 70 and 80 percent of homicides in that city. (Say, between husband and wife, employer and employee, or in the picture from the short Argentinian film “Till Death Do Us Part,” above, even bride and groom.)

Looking back over the crime book reviews I’ve written in the last few months, I find that when gun violence occurred in these stories, it is often of the more deliberate type, because the workings of the perpetrator’s mind are important to the story, the crime’s motivation, and its ultimate solution. But sometimes, both types occur: a spontaneous, “heat of the moment” crime leads to a chain of deliberate cover-up assassinations; or, conversely, tracking down the perpetrators of a well-planned crime leads to a deadly, reactive confrontation. But the two types of violence are definitely bifurcated in the way Ludwig describes, and the distinction between them makes perfect literary sense. Scott Turow’s recent novel, Presumed Guilty, is a good example of a crime thought to be a System 2 crime that turned out to be something very different.