Why Does Mass Killing Happen?

Crimes of the State | Week 3, Lecture 6

Professor Julian E. Gerez

April 15, 2026

Roadmap: Why does mass killing happen?

  • Last time:
    • What is genocide? What are the problems with the definition?
    • Moses’ critique: permanent security
    • Valentino’s alternative: mass killing
    • Any questions from Monday?
  • Today:
    • How do social scientists study mass killing?
    • What do existing theories get right? Wrong?

Is it possible to study mass killing scientifically?

What is science?

Our core goal is the accurate description of causal relationships (this is hard!)

  • A change in X produces a change in Y
    • E.g., wearing a seatbelt reduces the probability of dying in a car crash
    • E.g., dehumanizing attitudes cause mass killing(?)
  • When X and Y merely move together without a causal link, this is a spurious correlation
    • E.g., ice cream sales and drowning deaths both rise in summer

A line graph showing a strong correlation between the popularity of the 'surprised pikachu' meme and the number of middle school teachers in Puerto Rico from 2010 to 2022. Both lines remain low until 2018, where they spike dramatically together, peaking in 2019.

Spurious correlation between Surprised Pikachu and teachers in Puerto Rico

Surprised Pikachu

What is a theory? What makes a good theory?

  • Theory: A body of statements that systematize knowledge of, and explain, phenomena
    • Not just what happened, a theory is a story that explains how and why things are related
    • Example: People get wet when it rains because water falls from the sky and hits them
  • Theories generate hypotheses: testable, falsifiable predictions that follow from the theory
    • “If my theory is correct, then I should expect to see A, B, and C in the world”
      • If it rains, people without umbrellas get wet
      • If people use umbrellas, they stay drier
      • If there is no rain, people don’t get wet
    • If we observe A, B, and C, the theory is supported, if we don’t, the theory needs revision
  • Theories are never fully proven, only supported or undermined by accumulating evidence
  • In social science, theories are usually probabilistic
    • X increases the likelihood of Y, not that X always produces Y

Logic and social science

Consider the claim: “Oversleeping makes you late to class”

  • Oversleeping = the \(X\) or explanatory variable
  • Lateness = the \(Y\) or outcome variable

This theory produces falsifiable hypotheses:

  • If you oversleep and are late to class, the argument is supported
  • If you oversleep and are not late to class, the argument is not supported

But even if we are correct: we cannot conclude all students who are late overslept

  • For example, there might have been a traffic accident
  • Even if the student got up on time

Logic and social science

  • Oversleepers are more likely to be late, but not always (probabilistic, not deterministic)
  • Not all students who are late overslept (cannot reverse the logic)
Oversleeping students Students stuck in traffic/accident Students who are on time Students who are late

Why this matters for studying mass killing

  • Most major theories of genocide and mass killing identify factors that are very common
    • Social cleavages, dehumanization, national crises, authoritarian governments
  • But mass killing is rare relative to how often those factors are present
  • The key question is not: does X co-occur with mass killing?
  • It’s: Does X reliably distinguish societies that experience mass killing from those that do not?

Explaining mass killing

Social cleavages and dehumanization

  • Deep ethnic, racial, religious, or class divisions may create conditions for genocide
  • Polarization \(\rightarrow\) intergroup conflict \(\rightarrow\) erosion of moral obligations toward the out-group
    • Dehumanization: out-groups treated as animals or as inert (e.g., prisoner numbers)

Cover of Kangura, a Rwandan Hutu-extremist newspaper that used dehumanizing language against Tutsis ahead of the 1994 genocide

A Rwandan extremist magazine “Tutsi: Race of God!” and “What weapons will we use to win over the cockroaches for good?”

Screenshot of news coverage of President Trump describing undocumented immigrants as 'animals' at a 2018 roundtable

“In some cases they’re (migrants) not people, in my opinion … These are animals, OK, and we have to stop it.”
  • …But dehumanization was not really prevalent in Cambodia, China, or USSR!
  • And many deeply divided societies do not have mass killings

Authoritarian personalities or obedience

Individuals as psychologically predisposed to commit atrocities. For example, “F-scale”:

  • Rigid adherence to conventional values,
  • Submissiveness to authority figures,
  • Aggressiveness toward out-groups,
  • Opposition to introspection and creativity, etc.

You can take it here! (https://www.anesi.com/fscale.htm)


Your reactions to the authoritarian personality scale

Obedience, conformity, compliance

  • Obedience: the change of an individual’s behavior to follow a demand by an authority figure

  • Conformity: the change in a person’s behavior to go along with the group

    • Even if they not agree with the group
  • Compliance: conforming to an implied or explicit request in public

    • Even if they disagree privately

Tests of compliance with authority

Arendt, the “banality of evil”: ordinary people can be evil because of unreflective compliance

  • Milgram experiment: 65% of subjects administered what they believed were lethal shocks
  • Asch experiment: subjects conformed to an obviously wrong group consensus
  • Stanford prison experiment: “guards” rapidly adopted abusive behavior toward “prisoners”

Diagram of the Milgram experiment

Example of treatment in Asch experiment

What personality and obedience do and do not tell us

“Arrests” in the prison “experiment”

“Inmates” in the prison “experiment”
  • Obedience, conformity, and situational pressure are real and powerful

  • They help explain how ordinary individuals participate in mass killing once it is underway

  • But they cannot explain why mass killing begins in the first place

  • These mechanisms exist in virtually all societies

\(\rightarrow\) cannot distinguish rare cases where mass killing occurs from the majority where it does not

Valentino’s argument: “A few bad men”

  • Mass killing does not always require widespread public support, only passivity

  • A well armed, well organized minority can generate mass violence against unarmed victims

  • Starts with leaders (political/military)

The strategic perspective: mass killing is most accurately viewed as an instrumental policy

  • A strategy designed to accomplish leaders’ important political or military objectives

  • Leaders resort to it when they perceive it as the best available means to achieve specific goals

  • It is a “final” solution in two senses:

    • It is permanent: it removes the need for future efforts
    • It is final: usually the last in a series of less violent attempts

Evolution of policies and moving to mass killing

  • Perpetrators seldom view mass killing as an end in itself

  • They typically try less violent options first: removal, segregation, repression, etc.

  • These preliminaries strategies are preferred because they may face less resistance

  • Mass killing becomes attractive for:

    • Radical communization
      • Massive societal changes (communist policies like agricultural collectivization)
    • Counterguerrilla warfare
      • Guerrillas rely on civilians for support
      • Civilians are largely defenseless and easier to engage than guerrillas
    • Settler colonialism
      • Removal of populations to open land for settlement or resource extraction
    • Perceived existential threats (might be result of racism, nationalism, etc.)
      • Existential implies it can only be countered by removal
      • If expulsion cannot be achieved (people resist or there are too many)…

How to approach social science readings

  • Do not be intimidated by unfamiliar methods/math
  • Before you read the rest of the article, read the introduction and conclusion to get a roadmap
  • Make sure you understand the argument and evidence
  • If you still don’t understand, come to office hours!
  • A variable is a characteristic that takes on different values
    • An outcome variable \(Y\) is one we want to explain
    • A explanatory variable \(X\) is one we believe accounts for change in the outcome
  • Our goal: how is a change in \(X\) associated with a change in \(Y\)?
    • Does \(X\) make \(Y\) increase or decrease?
    • Does \(X\) make \(Y\) increase or decrease by a lot or a little?
    • Are there other variables that shape the relationship between \(X\) and \(Y\)?
  • You will never be tested on math!

For Monday: displacement, disappearances,and torture

  • Next week we turn to three more specific forms of state violence
    • Why might a regime displace a population instead of killing them?
    • How do disappearances work as a state strategy?
    • What is torture? What purposes does it serve?
    • Are these distinct from mass killing, or continuous with it?

Payne, Caroline L., and M. Rodwan Abouharb. 2016. “The International Covenant on Civil and Political Rights and the Strategic Shift to Forced Disappearance.” Journal of Human Rights 15(2): 163–188.

(Available on Perusall via Canvas)