Modeling Conflict. Thomas Chadefaux Chair of Sociology, in particular of Modeling and Simulation

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1 Modeling Conflict Thomas Chadefaux 1

2 Why We Fight War as the result of irrationality Human nature Psychology Evolutionary perspective War as the outcome of calculated, rational decisions Structure of the system Power shifts Arms races Bargaining failures 2

3 Modeling Rational Actors Game Theory Actors are strategic: forward and backward-looking Actors draw the best inferences given Available knowledge Constraints Maximize their payoffs given a set of preferences Advantages: Clarity, tractability Formal proofs Disadvantages Cumbersome Strong assumptions about cognition 3

4 Modeling Irrational Agents Agent-based models Limited cognition Large number of agents Typically non-strategic Advantages Ease of use Ability to model large number of agents Ability to include many parameters Disadvantages Lack of transparency Parameter overload Difficult to infer the core mechanism 4

5 Human Nature? 5

6 Two opposite views Hobbes: Endemic `warre à life is `poore, nasty, brutish, and short (Leviathan, 1651, 13) Rousseau: Harmonious living. Agriculture, demographic growth and private property are what brought war 6

7 Of Beasts and Men Goodall study in Tanzania Infanticide Intraspecific killing = the norm Rate of intraspecific killing among humans is often greatly inferior to other animal species 7

8 Did Hunter-Gatherers Fight? The Australian Lab Support for Rousseau much leisure Healthy Support for Hobbes widespread infanticide High homicide rate Widespread intergroup fighting 8

9 A men problem? Male death rate far higher: 15% of adults die as a result of inter and intragroup violence 7% women 24% males Women participate in battles, but mostly as support rarely in fighting 9

10 Bargaining Failures 10

11 A Simple Bargaining Model Two states negotiate over a territory of value 1 Each has some probability of winning: p for A, and (1-p) for B War is costly: costs c à expected values of fighting: For A: (1)p + (0)(1-p) c = p - c For B: (0)p + (1)(1-p) c = 1-p-c 11

12 The Fundamental Puzzle p-c c 1-p-c A B War is always inefficient ex post After the war, at least one party always regrets 12

13 Why War then? If war is always inefficient i.e., there is always an agreement that would leave both parties better off then why does it ever happen? Think about reasons why the two states may fail to reach an agreement in the bargaining range? 13

14 Why Bargaining Fails 1. Indivisibilities Some issues are inherently non-divisible Ipod Holy sites (e.g., Jerusalem) Thrones Why? Physically indivisible Emotional value Impractical Can you think of solutions? This can lead to the disappearance of the zone of agreement 14

15 Why Bargaining Fails 1. Indivisibilities: solutions Physical Division Very problematic Lottery. Problems: Commitment Ethics Rotation Destroy or give away Sell Compensation 15

16 Why Bargaining Fails 2. Private Information and Incentives to Misrepresent A wants at least this much B wants at least this much A B A pretends she wants at least this much B pretends he wants at least this much 16

17 Why Bargaining Fails 2. Private Information and Incentives to Misrepresent Even if, say, A is honest, B will discount what she asks for A wants at least this much B wants at least this much A B A says the truth about what she needs But B thinks A must be lying, so asks for this 17

18 Why Bargaining Fails 2. Private Information and Incentives to Misrepresent: Solutions Signaling. Two types Tie your hands -> audience costs Sunk cost -> display of force (e.g., missile tests) Slippery slope Escalation Small conflict Intelligence Mediation 18

19 Why Bargaining Fails 3. Power Shifts Large and rapid shifts in power caused by: Industrialization Arms races Mobilization Power A commitment problem A state may choose to fight now because it fears having to fight later Power Transition Time 19

20 Empirical Evidence Mixed Some major wars support this pattern WWI and WWII: Germany passes UK & then starts war BUT WWI does not begin with UK & Germany Many other Power Transitions have no wars US-UK, USSR-UK, etc. cinc cinc Germany year USA UK UK year 20

21 Why Bargaining Fails 3. Power Shifts: Solutions Trust-building Withdraw troops from border Negotiate disarmament E.g. Washington naval treaty Compensation E.g. partition of Poland 21

22 Modeling Conflict Using Agent-based Models 22

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25 States made war and war made the state (C. Tilly) 25

26 Geosim Lars-Erik Cederman, 1997 Download from growlab States are hierarchical, bounded Interact in a network on a grid 26

27 Possible Outcomes 27

28 Emergent Results 28

29 Using Geosim to address real-world problems e.g. 1: The distribution of war sizes Cumulative Frequency distribution of severity of interstate wars,

30 Distribution of war sizes 30

31 State Sizes 31

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33 Growing Democracies 33

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35 Growing Sovereignty 35

36 REFERENCES Cederman, Lars-Erik Emergent Actors in World Politics: How States and Nations Develop and Dissolve. Princeton: Princeton University Press Tilly, Charles Reflections on the History of European State-Making. In The Formation of National States in Western Europe, edited by C. Tilly. Princeton: Princeton University Press Tilly, Charles Coercion, Capital, and European States, AD Oxford: Basil Blackwell 36