Violence as a Contagious Disease

This is fascinating:

Intuitively we understand that people surrounded by violence are more likely to be violent themselves. This isn’t just some nebulous phenomenon, argue Slutkin and his colleagues, but a dynamic that can be rigorously quantified and understood.

According to their theory, exposure to violence is conceptually similar to exposure to, say, cholera or tuberculosis. Acts of violence are the germs. Instead of wracking intestines or lungs, they lodge in the brain. When people, in particular children and young adults whose brains are extremely plastic, repeatedly experience or witness violence, their neurological function is altered.

Cognitive pathways involving anger are more easily activated. Victimized people also interpret reality through perceptual filters in which violence seems normal and threats are enhanced. People in this state of mind are more likely to behave violently. Instead of through a cough, the disease spreads through fights, rapes, killings, suicides, perhaps even media, the researchers argue.


Not everybody becomes infected, of course. As with an infectious disease, circumstance is key. Social circumstance, especially individual or community isolation ­—people who feel there’s no way out for them, or disconnected from social norms ­—is what ultimately allows violence to spread readily, just as water sources fouled by sewage exacerbate cholera outbreaks.

At a macroscopic population level, these interactions produce geographic patterns of violence that sometimes resemble maps of disease epidemics. There are clusters, hotspots, epicenters. Isolated acts of violence are followed by others, which are followed by still more, and so on.

There are telltale incidence patterns formed as an initial wave of cases recedes, then is followed by successive waves that result from infected individuals reaching new, susceptible populations. “The epidemiology of this is very clear when you look at the math,” said Slutkin. “The density maps of shootings in Kansas City or New York or Detroit look like cholera case maps from Bangladesh.”

I am reminded of this paper on the effects of bystanders on escalating and de-escalating potentially violent situations.

Posted on January 28, 2013 at 6:07 AM40 Comments


Jb January 28, 2013 6:50 AM

The key is not “violence is a meme” but how closely it’s spread resembles the spread of diseases, so that the same techniques for tracking work.

Clive Robinson January 28, 2013 6:58 AM

It may run deeper than we think.

There is growing statistical evidence that the anti pinking / knocking agent tetraeythylelead (TEL) is strongly linked to both the rise in crime and where TEL gets banned the fall in crime with in both cases an aproximate offset of 20 years. Further the shape of the rise and fall is in line with the way TEL was introduced and more importantly how it was removed. A phased withdrawal of the use of TEL producing a much more gradual fall in crime than that of a blanket ban on TEL.

The conclusion is that TEL effects basic neurological structure in developing brains, which causes changes towards anti-social behaviour.

It would be interesting to compare the maps from this study to basic crime rate maps and then the historic maps.

There is also “group think” to consider, it’s known that whilst one on one violence is not unknown it is more usual to have three or more attackers on another individual, especialy if that individual did not provoke the atttack in the normal sense (that is by facing off / insulting, as opposed to just being in the wrong place or wearing the wrong clothes or being the wrong type).

It has been suggested that this group think is what gives rise to “gang ceremonies” where an individual has to “earn their colours” by committing an apparantly random act of violence at the direction of the gang leader. And if the individual trying to earn their colours baulks or hesitates then they know the rest of the gang will attack them with extream violence.

In some respects it has been likened to “blood rights” practiced in hunting and religion, which are still present all be it symbolicaly in the likes of Christianity (blood and wine of eucharist etc).

sd4f January 28, 2013 7:06 AM

I’m very sceptical of public health approaches to human behaviour. Certainly in the gun control debate, the public health approach is prejudiced on the assumption that more guns equals more deaths, time and time there is clear cut evidence that the public health approach is wrong and biased.

While I’m no criminologist, certain sorts of violence have been linked to socio-environmental factors, and socio-cultural factors. The wired article offers no compelling argument why violence is contagious, however all suggestions in the article are treating that like an established fact, which in my opinion, the notion is the critical aspect that should be tested.

coc January 28, 2013 7:21 AM

Yes, I agree, it could be explained through the meme perspective as it pushes one of those psychological “buttons”, which is fear, like saying “hey this is an effective way to preserve your genes, getting rid of everybody else” hoping from mind to mind through media…

Winter January 28, 2013 7:36 AM

“There is growing statistical evidence that the anti pinking / knocking agent tetraeythylelead (TEL) is strongly linked to both the rise in crime and where TEL gets banned the fall in crime with in both cases an aproximate offset of 20 years.”

TEL was used everywhere. From Switzerland to Indonesia. So pray, why should violence in the USA be higher than in Switzerland because of TEL?

AGS January 28, 2013 7:42 AM

Could these factors: the corruption of policing forces, economic forces, addictive drugs, gangs be as the forces behind the context of spreading diseases? Yes.

But, we could end up with a thought police society if we do not carefully tread in this direction.

There are obviously factors involved here which are unknown to researchers , just as the people of the day of the Black Death were unaware of the factor of rats and fleas.

Vles January 28, 2013 8:18 AM

“The underlying theme is learned behavior. That’s what gets transferred from person to person,” said Deanna Wilkinson, a professor in Ohio State University’s Department of Human Development

Rowell Huesmann, a psychologist at the University of Michigan, echoed Wilkinson’s point. “The contagion of violence is really a generalization of the contagion of behavior,” he said. “How do cultures transmit norms and beliefs across generations? It’s through observation and imitation. There’s no genetic encoding.”

Would have been great to use the opportunity to segue a little into something I’m fascinated with and what societal and individual factors/pressures cause them to fire.: mirror neurons… but alas no mention.

Flipped it:
Is It Time to Treat Violence Like a Contagious Disease?
Is It Possible then to Treat Good Acts Like a Contagious Disease?

(Do violent acts come about because of the absence of good acts? Like an imbalance – another metaphor – in the intestinal flora of good bacteria vs bad bacteria? For what is that which we call evil but the absence of good?)

Tongue in cheek:
I am reminded of this video on the effects of bystanders on escalating and de-escalating potentially violent situations.

Ollie Jones January 28, 2013 9:15 AM

People working in human services and ministry have known that suicide can become epidemic, and that it has a mimetic means of transmission. The single word for that is “copycat.”

Practically speaking, public health people have worked out good ways of slowing down epidemics. Interrupt the spreading. Intervene in identified cases of illness. Educate the public to resist infection. When we cope with suicide epidemics, those tools, properly used, help a lot.

In a recent epidemic (which claimed two lives, and in which interventions worked in a few other cases), I’ve heard people say, “oh, it’s just copycat suicide.” Correct, except for “just.”

bitmonger January 28, 2013 9:17 AM


The TEL studies actual show there is a correlation that is robust in other countries not just in the US. TEL is not an explanation for the total amount on crime in the US, but it may be a better causal variable than income or which is surprising.

bitmongetr January 28, 2013 9:28 AM

There is also a discussion going on about how some people are more resilient to traumatic experiences. If two people are violently attacked why might one person fully recover and another suffer PTSD from which they never recover. How experiences will effect us is not well understood yet.

There are genetic markers of interest to resilience here that are being looked at. There is also research showing the presence of certain chemical markers after experiencing minor shock waves that might be a warning that PTSD symptoms could develop later.

Charlie January 28, 2013 9:49 AM

@s4df: You are absolutely correct that there are “critical aspect[s] that should be tested.” The problem is that there is plenty of evidence of the NRA taking direct action to make sure public health or epidemiological questions regarding guns and violence aren’t asked, let alone answered (

Gathering empirical evidence about the causes of violence is the scientific way to proceed, without which it’s not possible to make rational policy decisions. The evidence may lead to one to either favor or disfavor gun control (the facts don’t care), but in the presence of active censorship one cannot fairly decry public health oriented researchers of being biased.

RH January 28, 2013 10:55 AM

“The density maps of shootings in Kansas City or New York or Detroit look like cholera case maps from Bangladesh.”

Personally, it makes a ton of sense to me that the human brain has a dial for violence to match the violence it sees. It’s probably one awfully well tuned dial too.

MH January 28, 2013 11:32 AM

“They made him watch. He probably tried to turn away, and they wouldn’t let him. You call him a survivor? He’s not. A man comes up against that kind of will, the only way to deal with it, I suspect, is to become it.” – Malcom Reynolds describing the man that survived an attack by Reavers in Firefly.

Bob T January 28, 2013 11:47 AM

It’s so they can start saying that people who own guns have a disease that threatens public safety.

Johnston January 28, 2013 11:56 AM


TEL was used everywhere. From Switzerland to Indonesia. So pray, why should violence in the USA be higher than in Switzerland because of TEL?

Clive didn’t make an exclusive statement; he simply said there is evidence that TEL is a contributing factor in rates of violence.

Adrian January 28, 2013 12:15 PM

Several things occur to me:

  • Humans are violent animals. It is part of our nature. If violence is an “illness”, it is one we are born with.

  • Could these “geographic patterns of violence” be an example of the so-called clustering illusion?

  • There’s no credible evidence that exposure to violent media leads to real-life violent acts. If anything, violence has gone down instead of up as media consumption has increased.

moo January 28, 2013 12:22 PM

@Winter, everybody:

Here’s an interesting article about the links between TEL in the environment (i.e. leaded gasoline usage) and violence rates ~22 years later.

Apparently the correlation is very strong, and might account for as much as 90% of the variation in U.S. crime rates over the last several decades. Also this strong correlation has been found in local and state datasets, and national datasets from many different countries.

This slashdot comment is also interesting:

Apparently, TEL was known to be hazardous on exposure as early as 1923. The inventor of it poured it all over his hands in a media stunt to demonstrate that it was safe. What they concealed from the media was that it took him nearly a year to recover from the lead poisoning he got from that demonstration.

Jarrod Frates January 28, 2013 12:28 PM

@Adrian: The existence of a capacity for violence does not itself make a species violent. Almost all animals have a capacity for violence that is encoded into survival instincts. Even relatively peaceful creatures can lash out if threatened, even if only trying to create an avenue for escape.

There are also strong environmental factors at play. Consider pets who do not strike unless put into certain scenarios such as being injured. Their environment does not encourage violence and so they tend to shrink away from it.

Adrian January 28, 2013 1:04 PM

@Jarrod: If there’s anything I’ve learned from history it’s that humans aren’t like other animals when it comes to violent behavior.

paul January 28, 2013 1:31 PM

Interesting how the comments run. Much more about interrogating the messenger than thinking about — if the model is accurate — how this insight might eventually be used to lead to societies with less violence (which one presumes, perhaps wrongly, would be a good outcome.)

Michael Brady January 28, 2013 1:54 PM


“TEL was used everywhere. From Switzerland to Indonesia. So pray, why should violence in the USA be higher than in Switzerland because of TEL?”

Population genetics? To quote the classics:

“We’re Americans, with a capital ‘A.’ You know what that means? Do ya? That our forefathers were kicked out of every decent country in the world. We are the wretched refuse. We’re the underdog. We’re mutts!”

Or it could be something else…

v January 28, 2013 2:34 PM

I wonder how ‘real’ the violence has to be…
Given that violent computer games aim to be as realistic as possible I’m guessing they might be realistic enough…
One man’s entertainment is another man’s psychological impairment.

Rankin January 28, 2013 2:37 PM

I wonder when every negative aspect of human behavior is going to lose accountability and is merely going to be attributed to yet another “contagion”. If this idea takes widespread hold in the society, what would be the most likely defense of criminals in a court of law?

jb January 28, 2013 4:25 PM

@ Winter:

The TEL correlation is not to rates of violence, but to trends in violence. So Switzerland has always had less violence than the USA, but in both countries violence declined in similar proportions after the removal of TEL.

Obviously, there are other reasons why Switzerland is less violent than the USA, but TEL’s effect is clear.

sd4f January 28, 2013 5:46 PM

@Charlie, read the this article;

The reason why the CDC stopped getting funding is pretty clear, it’s not about banning research, it’s about not spending public money on bogus research.

Here’s a fairly quick explanation of Arthur Kellerman’s jaded figures, regarding chances of a gun owner being hurt, from this, it’s quite clear that his research is not factual.

Public health does look at epidemics, but i think it’s flawed trying to apply it to everything. Virus’ can infect people indiscriminately, so spotting a spreading trend is quite useful with contagious disease; whereas violence, i think it’s unnecessarily obfuscating the issues at hand. Some areas just have more violence because people are poorer and there is more social tension in the area.

Ultimately, I have no idea what is the cause and solution, but i think the public health approach is taking some very unscientific leaps of faith in some matters, and also ignoring well established criminological axioms.

jdgalt January 28, 2013 6:36 PM

This is typical of the hogwash nanny-statists put out when they want to ban something that is none of their business.

I submit that if the government would like to reduce violence, it can start by ceasing to behave in ways that provoke and justify violence, such as stopping and searching people for no valid reason. Abolish TSA, close all checkpoints that aren’t at the border, and generally go back to behaving in ways the government has business behaving, as opposed to unconstitutional attempts to predict crime (or to define it so vaguely that a cop’s judgment determines who is a criminal).

In short, the government needs to decide whether it’s going to be the people’s friend or our enemy.

Vles January 29, 2013 6:15 AM

Abolish TSA, close all checkpoints that aren’t at the border, and generally go back to

I suspect they might, after they’ve fingerprinted the world, swapped for everyone’s DNA and combined that with information of each FB’s and tweets…

VP January 31, 2013 4:21 PM

I would say it is important to distinguish violence as response on outer aggresion and /or abuse (kid kills bullies in a high school, prisoner kills cell mate who raped him, etc, – see ‘Law Abiding Citizen’). That is reactive violence when victim is the source of the problem. It is basically resolve problem /deliver real justice when legal system is disfunctional. In those cases without addressing the root source of the violence problem is focused on means (weapon – poor man lawyer) rather than the root of the problem.
Versus proactive violence when it is used to achieve goals which are not reasonable at all or applied on misplaced target (kids killed in the thearter). That is personality problem first.

David February 1, 2013 6:07 PM

@VP: you’re describing the difference between “force” and “violence”. The defining characteristic of the latter is the “violation” of another.

Self defense (i.e., using force to stop violence) is not violence (nor is it vigilantism, but that’s another article :).

S. T. Bond February 4, 2013 5:42 PM

The presence of guns is not the cause of violence. There are places which are saturated with guns but have low crime rates. Most rural areas that have opportunity for hunting have many guns. People respect them. It is inequity and violence that causes violence.

Michael February 7, 2013 12:33 PM

I don’t think that there is any need to gratuitously use a desease transmission metaphor or worse think its true and not just a metaphor. Behavioral explanation is fine. People do what they see and act the way they are taught. Anyway if you say its a disease, then you create confusion about how to deal with it. What would be the “cure”? Although I suppose that some things that apply to epidemiology might apply to violence. But still at some point it won’t be appropriate and you will have more bad thinking. Violence is not a disease. It may be caused by “mental illness”. But why bother unless you’re looking for funding. And I am uncomfortable with calling violence a disease because its a kind of sensationalization that I think is indicative of of a lack of precision AND a lack of a language to discuss violence on ontologically.

Lee Carré February 7, 2013 3:41 PM

Many commenters would benefit from watching Michael Moore’s Bowling for Columbine, which addresses many of the questions and suspected causes of violence, especially in the USoA.

Adrian said:

Humans are violent animals. It is part of our nature. If violence is an “illness”, it is one we are born with.

I strongly suggest reading The Myth of Man the Killer, which cites opposing evidence from, among other sources, military experience.

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