Stochastic terrorism part 1 – The sand pile effect

I have written in the past comparing the math behind American gun violence as unnervingly similar to the random-but-probabilistic math of lotteries. Another descriptor for this phenomenon pops up from time to time, and it has again after the mail bombs and the tragic Pittsburgh synagogue killings of this past week, and that is the term stochastic terrorism.

What is stochastic terrorism, and does the math of gun violence in America support the claim? In this post and the next I will look at two ways to look at the math. In short, stochastic terrorism is similar in its math to anthropogenic (human-caused) climate change. It’s very real, we’ve decidedly raised the “temperature,” and yet the deniers will always be able to dodge direct culpability.

Stochastic means “randomly determined,” and so the idea behind stochastic terrorism is that it is possible for people with bad intentions to use the internet and other mass media to incite random, unknown-to-them perpetrators to carry out violent acts against their targets. Rather than a clear one-to-one “cause and effect,” there is instead a statistical predictability that the acts of terrorism will occur. But at the same time, it is impossible to individually predict who that perpetrator is or when the strike will occur. The perpetrators of stochastic terrorism then get to claim “clean hands.”

Let’s get specific. Did the President Trump’s (incorrect) assertion that a current “migrant caravan” from Central America headed to the southern border of the United States was funded by Jewish philanthropist George Soros cause in some way the murder of eleven synagogue worshipers in Pittsburgh on October 27, 2018?

The frustrating part of attributing stochastic terrorism to this specific act is that there will never be any direct link, although in this case the domestic terrorist apprehended at the scene has indeed posted in angry terms about this very migrant caravan on the social media site Gab. [1] That is, frankly, about as close a link as you will get in these cases, but was it the trigger that caused the mass murder? Let’s start by looking at the sand pile effect.

The sand pile effect

In a recent post about climate change, I used the example of the sand pile effect to illustrate a similar relationship between individual catastrophic “rain events” and anthropogenic climate change. While it is impossible to tie any one specific hurricane or multi-inch “rain event” to climate change, we can use the mathematical example of how a sand pile builds a conical shape over time as sand pours onto the top. At some “random” point, our nice conical pile will suddenly collapse into a jumbled mess. In weather terms, increased amounts of moisture in the atmosphere at higher global temperatures will eventually “collapse” in deluges of rainfall in geographically small areas over a short amount of time.

While you cannot predict exactly when the sand pile will collapse, you can use information about the nature of the sand, the rate of drop, and historical observations to create an accurate probability distribution that might say, for instance, that there is a 90% chance that the sand pile will get “this big” and then collapse between Time X and Time Y. Statistically, this is correlation and causation, but finding that one grain of sand that “caused” the collapse is both impossible and, frankly, irrelevant. All of the noted factors come into play, although some more than others, in determining how high the pile will build and the range of time over which it will build until its sudden collapse. That one “cause of collapse” grain of sand is like the classic straw that breaks the camel’s back.

In a similar manner, something is happening with gun violence rates in America that makes us different from the rest of the developed world. Some combination of factors has “raised the temperature” in ways not seen elsewhere. One correlating, but not necessarily directly causative, factor is the number of guns per capita in this country, which is unmatched in the developed world.

Rattner graph on gun availability

Source: Steven Rattner – MSNBC

Importantly, note that the greater majority of gun owners in the United States do not act out violently with their weapons. Likewise, we have millions of people in the country suffering from mental illness, another often-cited causative factor of gun violence, but far more are more often victims of violence rather than perpetrators.

The “sand pile effect” suggests that these and numerous other factors, such as the fecund online “memes” of incendiary political rhetoric that flood social media sites, “pour more and more sand” on the “potential gun violence” pile. There are likely tens of thousands of Americans “living on the edge” on any given day, and at some random point, someone is going to “collapse” like the sand pile. And if there is a “high lethality” weapon available close at hand, the results will likely be tragic.

Note that this “sand pile collapse” happens much more frequently and sadly with the use of a gun in suicide as compared with mass gun violence. In an earlier post I discussed some of the evidence that simple availability of a firearm “changes the odds” of suicide dramatically, and so a more individual version of the “sand pile effect” is also likely occurring here as well.

Parsing out the probabilities

In the terms of this “sand pile” model of mass gun violence, you cannot predict the exact “grain of sand” event or person who “collapses the pile” here. That person is likely both a probabilistic and random “winner” of a sick lottery, although you likely could create a list of the “highest propensity to collapse” people. So finding the specific “who” is very difficult to do, however, we do have some control over the “sand coming onto the pile,” both in terms of quality and quality.

Incendiary political rhetoric plus the easy availability of high-lethality weapons remain the two most likely “sand pile” builders contributing to mass gun violence in the United States, and these two tag us as different from most of the rest of developed world. We can also place certain demographics of the population in a “low risk of mass violence” pool, for instance the 50% of the population carrying XX chromosomes. Some things are so obvious that we refuse to confront them.

Did President Trump’s particular remarks about “migrant caravans” cause the Pittsburgh shooting? The best answer here is that we have a crisis of “human-caused warming” of political tension, and the intentional “riling up” of fragile individuals who own lots of guns. The “odds are” that some speech somewhere will be a trigger for someone. Then again, we could reduce the amount and rate of sand piling onto the sand pile if we had the political will. Other countries do it.

Part Two of this post updates the numbers demonstrating the creepy “Poisson randomness” (pronounced “pwa-sohn”) of gun violence in America. We can, it turns out, predict quite accurately when the next act of mass gun violence will occur. Just not where. Subscribe to this blog by entering your email address in the box to the left of your screen, or click on the Facebook or Twitter icons to be notified of new posts.

Part Two of this series has now been posted.


  1. “Synagogue Shooting Suspect Threatened Jewish Groups, Pushed Conspiracies.”, 27 Oct. 2018.

2 thoughts on “Stochastic terrorism part 1 – The sand pile effect

  1. Pingback: Stochastic terrorism part 2 – the mass shooting lottery – When God Plays Dice

  2. Pingback: When innumeracy kills – When God Plays Dice

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