But they seemed so normal!

Boston has done well. Within a week they got the two bombers who killed and maimed Bostonians at the Marathon finishing line. Catching a determined bomber is not easy, but in retrospect these bombers were pretty obviously stupid, or at least determined to get caught or killed. Puffed up self-confidence was their undoing. They did nothing to escape in the precious (to a terrorist) immediate aftermath of the bombing, when normal human beings are helping the dying and the wounded, and the Police are stretched to the limit. They planted the bombs with minimal attempts to cover their faces or disguise their appearance. Perhaps they did not care, or did not realise how quickly they might be identified.

Then, once their faces were on public display they shot a policeman, and embarked on a high speed car chase, flinging grenades at their pursuers. Unless you have a proximity fuse, this is a poor defense. Their shoot out was an attempt at going out in a blaze of glory, and ended with the survivor getting into yet another shootout. Suicide by cop seemed to be their ambition.

In fact, Bostonians have done well, and the official agencies only well enough. It was fellow students who recognised the bombers immediately, and since the suspects were still in town it was already the end of the road for them. It was also a Bostonian who, once he was allowed out of his house, checked his boat in his back yard and found the bleeding and sleeping 19 year old, who should already have been located by a competent policeman with a dog. The understandably jumpy and heavily armed police could probably have done more basic checking: it is easier to hide in a garden than to break into a house, which runs the risk of running into a resident. Too many of them seemed to be in armoured vehicles, and not enough of them just poking about.

The FBI will have the usual questions aimed at it: why did they not realize that this particular trawler of Jihad websites was going to move from just looking to bombing and killing? The conversion rate from fantasist to activist might be 100 to 1 (I do not have the figures, but even 25 to 1 would make life very difficult). How many Islamists can one watch at one time? This is not to say that the problem is impossible to solve. What does one expect to obtain from an interview with a suspect, given the low rate of prediction achieved by most interviews? More reprehensible is the failure to weight indicators: a six month stay abroad in a quasi-war zone should merit at least another look. The regression equation or discriminant function analysis may need revision.

Statistical prediction is usually better than clinical prediction, as Cronbach and Meehl found in 1954. That supposedly cunning, penetrating, highly sophisticated face to face interview is less predictive than actuarial data obtainable by diligent recording of major behavioural events.

Meanwhile, what with social media we have an outpouring of data about them. Their family are giving the usual disbelieving responses (including stupid conspiracy theories) though their uncle had a robust disdain for their actions. As usual, most other people who knew them are astounded that they could have done the things they did. They did not “seem” to be mass murderers.

Why? Well, we are not all that good at detecting simple liars, of which there are many (usually we are little better than chance level at detecting deliberate deceit). We are even worse at detecting many lower frequency behaviours. Can you spot a man who privately looks at a lot of violent pornography? Can you spot a works supervisor who uses drugs or alcohol?  Can you tell which friend was cautioned by the Police for violence towards a spouse? Possibly some of them, but murderers are mercifully too rare for us to have much of a track record in detecting them. Mass murderers are even rarer, and much harder to spot. My brother met one, had a meal with him, and was none the wiser. Nor would I have been. http://www.yorugastories.com/2/post/2012/10/the-story-of-martn-el-ingls.html  

It is clear that normal social interaction is neither too taxing nor too revealing. In fact, it may be designed for precisely that purpose. We can associate for what we require, and keep many of our thoughts to ourselves. Courtesy and normal social interaction is a skill that most people can muster to some degree, but much of the inner life can go undetected. There is something of a pattern that mass murderers tend to be loners and misfits (and to be seeing psychologists), but that is by no means the rule.

Now, with the benefit of hindsight, some elements stand out: moments of boorishness, alienation, fascination with Jihad and inflammatory preaching. Not necessarily too predictive, sadly.  I note, at a mere clinical level, that one of my favourite indicators was mentioned: a change in appearance from more to less, or less to more, devout. In this instance the older, more dominant brother is said to have shaved off his devout beard a month before the bombing. It could have been due to the practical need not to attract attention, or the psychological need to prepare for battle. Otherwise, thin pickings. As far as I know they did not dress in religious battle clothing for their final outing, or shave their heads. More background facts may emerge.

Some Americans are making the usual laments, asking: how come those to whom we gave refuge have turned against us? How could a decade of western life have not transmitted the ideals of the Enlightenment?  President Obama asked: “Why did young men who grew up and studied here as part of our communities and our country resort to such violence?” 

It may not seem much of an answer, but it seems that they did so because some people told them they should, and eventually it seemed a good enough reason. It is not a failure of the American welcome, given to so many, with few questions asked. It simply provided a good and uplifting explanation for their adolescent problems, even though those failures were hardly out of the ordinary. Great outrages often arise for trivial reasons. Asked why he had triggered a major prison riot, with warders held hostage on the roof with a noose round their necks, the ringleader was unable to give interviewers a coherent reason, other than the late delivery to his cell of his morning cup of milk.