Suckers for a good story

In the comments to the previous post, Brooksfoe, who I respect a great deal, points out that the narrative "Soldiers exposed to combat come home to kill" does not flunk the gut check test.

No, indeed, it doesn't. I can build a quite plausible story where combat makes people into crazy killers.

The problem is, it's just a story. History is full of those stories that turned out not to be true. As my commenter points out, I can also build a plausible story where combat makes you realize the sanctity of human life and makes you less likely to kill. Or where the amazing human capacity for compartmentalization makes it have no overall effect. A look at one piece of gross evidence--the massive return of combat troops post World War II does not seem to show evidence of a killing spree; homicide rates fall during the war (not surprising; we shipped our prime homicide age overseas by the millions, plus national emergencies tend to surpress both crime and suicide); rates return to their 1940 level in 1946, then fall rapidly, which is not what I would expect if combat is really so brutalizing. But lots of things changed, yadda yadda. The point is, there is usually more than one plausible story. To check whether your story is true, you need data.

The Times article purports to provide data. But it does not. It provides raw numbers without reference to the size of the relevant population. This is statistical garbage. I'm sure that some Ivy League graduates committed crimes during the same period, and some of them probably blamed it on their high stress upbringing. But this does not tell us anything without knowing how many Ivy League graduates there are.

Humans are designed by evolution to make some bad cognitive snap judgements. We are very prone to the post hoc, ergo propter hoc fallacy, because that was the safest way to bet when you're a naked, vulnerable east african plains ape. These heuristics are the best we could do on the veldt, but with time for cooler reflection, the problems become obvious.

In any group of a couple of million people between the ages of 18 and 24, some will be mentally unstable. Some will snap without warning--"He was such a nice boy". Some will commit spectacular, inhuman, surprising crimes which no one will ever hear about outside of their local area because unfortunately, young people snapping is not rare enough to make the national news. Some will drive drunk and be charged with vehicular homicide. Some will abuse their children. Obviously the people in their lives who are shocked by this behavior will associate the fact that they went to Iraq with the change, in the same way that parents of children with autism associate vaccines or other random events with the change that occurred in their children around age two. But that doesn't mean the event caused the change.

To know whether one event caused another, you would first want to know that the event you are seeking a cause for was actually unusual. That's why you need to know whether the homicide rate among veterans actually spikes when compared to a) soldiers who didn't go to war b) similar demographic groups among the population. The New York Times doesn't even try. Their work is not merely anecdotal silliness; it's anecdotal silliness masquerading as actual information. This puts my hackles up.