COINCIDENCE OR CAUSE? In 2011, Norwegian Anders Behring Breivik bombed government buildings in Oslo, and then went to a youth camp, where he shot and killed 69 people, mostly teens. As a player of first-person shooter games, Breivik stirred debate when he commented that “I see MW2 [Modern Warfare 2] more as a part of my training-simulation than anything else.” Did his violent game playing contribute to his violence, or was it a mere coincidental association? To explore such questions, psychologists experiment.

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