Understanding the Terror Contagion Hypothesis

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TLDRUpFront: A mass shooting terrorist incident in Buffalo, NY, appears to be a part of the continuing Great Replacement terror contagion. The terror contagion hypothesis is a new way of understanding the spread of violent radicalization, which leads to terrorist attacks such as in Norway, Charleston, Christchurch, Pittsburgh, El Paso, and now Buffalo.



Personal Note: The InfoMullet went on pause in late March from covering the war in Ukraine as I prepared to defend my Ph.D. dissertation in System Dynamics. I successfully defended the dissertation, “Lifecycle of Violence and Instability of Non-State Actors,” on April 20th, 2022. The first four chapters of the dissertation deal with research on the terror contagion hypothesis. And just last Monday I submitted a research proposal to specifically study the Great Replacement terror contagion as the first specific application of the generic terror contagion hypothesis.


A tale of two terror contagions.

In 1999, two perpetrators planned to use improvised explosives to kill their classmates at Columbine High School. When the explosives failed to detonate, the perpetrators improvised a mass-shooting attack that killed 13 people and wounded 24. A wave of media coverage generated by the fatalities broadcast the improvised rather than intended method and a misleading profile of the two perpetrators [1, p. 6]. Since then, at least 30 perpetrators, some born after Columbine, have seen themselves in that media-constructed representation replicating the improvised mass-shooting method, rather than the intended explosives method, to attack their schools resulting in over 100 killed since 1999[2, pp. 6–7]. As a seed event, Columbine defined and transmitted a violent ideology and a method for mass-violence terrorism attractive to young white men targeting schools or universities.

In Norway in 2011, a different perpetrator mixed xenophobia, white nationalism, and the “Great Replacement Theory” [3, p. 129] with a different template method for complex mass-shooting attacks.  This white nationalist terror contagion includes replications of Sandy Hook in 2012, the Charleston church shooting in 2015, and four attacks on houses of worship in 2019, including the Christchurch mosque, Pittsburgh synagogue, Poway synagogue, Halle synagogue shootings; the attack on a Wal Mart in El Paso 2019, the Hanau Germany attack of 2020 among others. These successful incidents caused over 600 casualties, including over 200 killed worldwide. An example of a near miss is the arrest and guilty plea of a self-described white nationalist Coast Guard Lieutenant, who planned a Norway-style attack in Washington DC in 2019.

The terror contagion hypothesis.

Simple system diagram of the terror contagion hypothesis.

The terror contagion hypothesis, developed through systems science and domain expertise, is that radicalization leading to mass-violence terrorism is a complex system of social contagion similar to a Werther contagion of celebrity suicide[4]–[7], with a clear causal structure [8]. A terror contagion is a form of social contagion spread through cultural scripts by terrorist incidents of mass violence. These cultural scripts convey a template ideology and a template method (A) based on specific grievances, moral outrage, and other social/cultural influence factors (B) within a given high-risk population (C). These templates must be suitable in terms of self-similarity and notoriety to the high-risk population; self-similarity in that they recognize themselves in the perpetrator’s identity, and notoriety in that they view mass violence as a source of celebrity rather than repulsion. The template ideology conveys a conspiracy narrative that explains the perceived grievance, identifies an out-group as responsible, and advocates violence to address it. The template method conveys instructions on how to conduct mass-violence terrorism. These templates operate in concert to activate a mammalian adaptation to predatory violence (D), leading to the next mass-violent incident (E). This incident spurs the spread of template ideology & method (F) due to the broad reach of media reporting (G). In celebrity suicide Werther contagions, the effect is short-lived because the celebrity of the suicide drives media attention. In a terror contagion, however, mass casualties generate media attention when perpetrators follow the template method, and terror contagions can become self-perpetuating. Each subsequently completed act of mass violence furthers the replication and spread of cultural scripts, sustaining the contagion of violent radicalization in the high-risk population.

These contagions are specific to a given high-risk population due to the different self-similarity related to grievances and conspiracy narratives determining which cultural scripts will be received or ignored. White nationalist terror contagion and school shooting contagion incidents may have more differences than similarities even though both involve a method of mass shootings. Furthermore, other terror contagions inspired by different violent ideologies targeting their high-risk self-similar populations could differ dramatically in template methods.

What is the Great Replacement terror contagion?

The ADL describes the Great Replacement Theory as a conspiracy narrative promoted by white nationalists on the impending destruction of the white race by genocide. Although the original great replacement theory concerned that Muslims were replacing white Europeans, it quickly expanded to a global audience of white nationalists incorporating racist, anti-Semitic, misogynist, anti-LGBTQ+, and anti-multicultural extremist views[9]. In Norway in 2011, a terrorist conducted a complex attack that killed 77 and injured 319 over multiple locations. The manifesto released by the terrorists as the attacks unfolded laid out in detail both his violent ideology of the great replacement theory conspiracy, but painstaking notes and instructions on the template method of how he prepared for and would conduct the attack. The high fatalities in Norway and online accessibility of the manifesto spread this template ideology and template method into the existing white nationalist social media networks, sparking the contagion. Subsequent mass shootings frequently cite the Norway 2011 manifesto and replicate its methods – down to publishing their manifestos and planning to be caught alive (a difference from the Columbine school-shooting terror contagion). Subsequent events took advantage of new mediums, including Reddit, 4Chan, 8Chan, and Discord, and incorporated these with an intent to make the event more viral, such as in the 2019 Christchurch shooting, which included a live stream of the event.


The white nationalist threat environment.

The Great Replacement terror contagion occurs within a broader white nationalist threat environment. The Department of Homeland Security recently described white nationalism as a pressing terrorist threat targeting racial and religious minorities, members of the LGBTQ+ community, and promoters of multi-culturalism perceived to undermine white nationalism. [10, p. 18]. White nationalism is a global phenomenon with violent radicals engaging in “outreach and networking” with foreign “like-minded individuals to expand their violent extremist networks[10, p. 18].” Our research on terrorism from 1995-to 2018 [5] identified 152 incidents in the United States and 303 in Western Europe related to white nationalist terrorism across all categories DHS mentions. White nationalist terrorism in the United States, compared to national averages, is more likely to succeed in completing attacks (90% vs. 83%), much more likely to cause property damage over $1M (35% vs. 8%), and cause far more casualties on average (7.5 vs. 3.1 casualties). With 9/11 and the 2017 Las Vegas Casino attack removed as outliers, white nationalist terrorism between 1995-2018 accounted for ~25% of all domestic terror incident attempts and over 60% of all casualties recorded[11]. The threat continued rising past our dataset end in 2018 [12], as white nationalists “conducted more lethal attacks in the United States than any other…movement[10, p. 18].”


Was Buffalo part of a Great Replacement terror contagion?

It is too early to know for sure, but it looks probable. The InfoMullet tries hard to follow Clancy’s Razor against idle speculation on key details of complex, violent events in the first 72hours because the information frequently changes. In our research, we have seen multiple shooters across multiple locations resolve to one shooter in one location, or the reverse, while the race, gender, and purported social media accounts associated with the terrorist morph and change in the early hours as political ideologues attempt to project the latest incident on their opponents. It is often the first police briefing the day after and the three days subsequent (hence 72hours) where we get our first insights. However, sometimes the details take months or years to unravel fully.

Caveat lector, the evidence seems strong at this point the Buffalo shooting is part of the Great Replacement terror contagion. Even as breaking news was occurring last night, some distinctive template method markers were indicating potential replication, including:


  • Terrorist traveled a far distance to conduct attacks, as in Norway, Christchurch, and El Paso
  • Target location selected to target specific profile on ethnicity/race as in Charleston and El Paso or religion as in Christchurch, Pittsburgh, Poway, and Halle
  • Target location is a grocery store as in El Paso
  • Terrorist captured alive as in Norway, Charleston, Christchurch, Pittsburgh, Poway, Halle, and El Paso
  • Simultaneous release of manifesto communicating ideology and method as in Norway, Charleston, and Christchurch
  • Shooting victims targeted on a specific profile of ethnicity/race as in Charleston and El Paso or religion as in Christchurch, Pittsburgh, Poway, and Halle
  • Terrorist livestreamed themselves on a social media platform as in Christchurch
  • Terrorist carried the similar equipment (both by style and ratios) as Norway and Christchurch shootings


This morning, the alleged manifesto of the terrorist is making the rounds, and it makes his association with the Great Replacement contagion clear. He all but invokes those words while espousing a violent ideology and directly crediting past Great Replacement terror contagion terrorists, including from the Norway, Christchurch, El Paso, and Poway incidents leading to his violent radicalization and providing him an instruction manual on how to follow in their footsteps.


What can we do to counter Terror Contagions?

Although the terror contagion hypothesis is relatively new, we have over thirty years of solid research on strategies specifically designed to counter the spread of self-harm or violent social contagions. We know how Werther effects [4], [13], [5]; and how Papageno effects[7, p. 12],[14]; decrease suicide contagion spread. Also, simply recognizing that terror contagions exist and contain both ideological and method markers can equip schools, law enforcement, and the community with better risk assessment tools. If someone being investigated on a tip, lead or warning displays markers of a specific contagion, greater resources can be applied based on elevated risk and targeted interventions designed to counter that specific contagion. Also, if the contagion operates through cultural scripts through a specific causal mechanism that opens up novel intervention efforts at the system level to cut the feedback loop between a given incident and their targeted self-similar population. Asymmetric cultural script techniques include counter-reification, failure notoriety, and reducing script coherence. Because terror contagions are self-perpetuating, cutting the connective links to an incident can impede or eliminate future terrorist attacks.


Where can I find more on terror contagions?

As mentioned in the personal note, I spent the last six years researching terror contagions and creating computer simulations to study them as part of my Ph.D. In addition to the sources below, here are four papers related to this research:


“Profiles of Violent Radicalization: Analysis on key criteria of over 4,600 terror incidents in Western Europe and the United States from 1995-2018,” https://dx.doi.org/10.2139/ssrn.3957928.

“Root Causes of Violent Radicalization: The Terror Contagion Hypothesis,” http://dx.doi.org/10.2139/ssrn.3957919.

“Contingencies of Violent Radicalization: The Terror Contagion Simulation,” 10.3390/systems9040090.

“Countering Violent Radicalization: Comparing antiterrorism, counterterrorism and counter radicalization strategies.,”: http://dx.doi.org/10.2139/ssrn.3990014.



[1]            R. W. Larkin, “The Columbine Legacy: Rampage Shootings as Political Acts,” American Behavioral Scientist, vol. 52, no. 9, pp. 1309–1326, May 2009, doi: 10.1177/0002764209332548.

[2]            P. Langman, “Different Types of Role Model Influence and Fame Seeking Among Mass Killers and Copycat Offenders,” American Behavioral Scientist, vol. 62, no. 2, pp. 210–228, Feb. 2018, doi: 10.1177/0002764217739663.

[3]            J. Greenblatt, It could happen here: why America is tipping from hate to the unthinkable–and how we can stop it. 2022.

[4]            D. Phillips, “The Influence of Suggestion on Suicide: Substantive and Theoretical Implications of the Werther Effect,” American Sociological Review, vol. 39, no. June, pp. 340–354, Jun. 1974.

[5]            A. Schmidtke and H. Hafner, “The werther effect after television films: new evidence of an old hypothesis,” Psychological Medicine, vol. 18, no. 3, pp. 665–676, Aug. 1988, doi: http://dx.doi.org/10.1017/S0033291700008345.

[6]            J. A. Bridge et al., “Association Between the Release of Netflix’s 13 Reasons Why and Suicide Rates in the United States: An Interrupted Time Series Analysis,” Journal of the American Academy of Child & Adolescent Psychiatry, vol. 59, no. 2, pp. 236–243, Feb. 2020, doi: 10.1016/j.jaac.2019.04.020.

[7]            J. Domaradzki, “The Werther Effect, the Papageno Effect or No Effect? A Literature Review,” IJERPH, vol. 18, no. 5, p. 2396, Mar. 2021, doi: 10.3390/ijerph18052396.

[8]            T. Clancy, B. Addison, O. Pavlov, and K. Saeed, “Root Causes of Violent Radicalization: The Terror Contagion Hypothesis,” Manuscript submitted for publication., p. 33, Jan. 2022, doi: http://dx.doi.org/10.2139/ssrn.3957919.

[9]            “‘The Great Replacement:’ An Explainer,” ADL. https://www.adl.org/resources/backgrounders/the-great-replacement-an-explainer

[10]         “Homeland Threat Assessment October 2020,” US Department of Homeland Security, Oct. 2020. [Online]. Available: https://www.dhs.gov/sites/default/files/publications/2020_10_06_homeland-threat-assessment.pdf

[11]         T. Clancy, O. Pavlov, B. Addison, and K. Saeed, “Profiles of Violent Radicalization: Analysis on key criteria of over 4,600 terror incidents in Western Europe and the United States from 1995-2018,” WPI Department of Social Science and Policy Studies Working Papers., vol. 2021, no. 004, p. 33, Nov. 2021, doi: https://dx.doi.org/10.2139/ssrn.3957928.

[12]         J. Collins, “A New Wave of Terrorism? A Comparative Analysis of the Rise of Far-Right Terrorism,” Perspectives on Terrorism, vol. 15, no. 6, pp. 2–22, Dec. 2021.

[13]         S. Stack, “Media coverage as a risk factor in suicide,” Journal of Epidemiology & Community Health, vol. 57, no. 4, pp. 238–240, Apr. 2003, doi: 10.1136/jech.57.4.238.

[14]         M. Sisask and A. Värnik, “Media Roles in Suicide Prevention: A Systematic Review,” Int J Environ Res Public Health, vol. 9, no. 1, pp. 123–138, Jan. 2012, doi: 10.3390/ijerph9010123.


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