San Bernadino. Paris. Nice. Orlando. Munich. Dallas. The recent cluster of horrific events make us wonder: Is such violence socially contagious?
Or do killings come in clusters merely for the reason that streaks pervade hospital births and deaths, or basketball shots and baseball hits—because random data are streakier, with more clusters, than the human mind expects? World War II Londoners noticed seeming patterns to where German bombs hit. Were the East Enders receiving more than their share because the Germans were trying to alienate the poor from the rich? After the war, a statistical analysis revealed that the bomb dispersion was actually random.
But some social happenings are contagious. Airplane hijackings and suicides occur in nonrandom bunches. After Marilyn Monroe committed suicide in 1962, 303 more people than average took their lives that month. When the suicide is well-publicized (if it’s a celebrity and is reported on television), copycat suicides become especially likely.
Media experiments, from the Bandura Bobo Doll experiments to the present, indicate that violence-viewing also evokes imitation. So, in some cases, have real-life murders and mass killings, as happened with the rash of school shootings during the eight days following the 1999 Columbine High School shooting rampage. Every U.S. state except Vermont experienced threats of copycat attacks. Some mass killers also are known to have been obsessed with previous mass killings.
We can hope that mass killings, like school shootings, may subside over time. But given a possible terrorist motive—to influence the 2016 U.S. presidential election, by driving support toward an authoritarian law-and-order candidate—I am apprehensive.