• Choose a category
• All
• Classic-Fiction

By Root 1036 0

of cause and effect—that in order for A to be said to cause B, A must precede B in time. If a billiard ball starts to move before it is struck by another billiard ball, something else must have caused it to move. Conversely, if we feel the wind blow and only then see the branches of a nearby tree begin to sway, we feel safe concluding that it was the wind that caused the movement. All of this is fine. But just because B follows A doesn’t mean that A has caused B. If you hear a bird sing or see a cat walk along a wall, and then see the branches start to wave, you probably don’t conclude that either the bird or the cat is causing the branches to move. It’s an obvious point, and in the physical world we have good enough theories about how things work that we can usually sort plausible from implausible. But when it comes to social phenomena, common sense is extremely good at making all sorts of potential causes seem plausible. The result is that we are tempted to infer a cause-and-effect relationship when all we have witnessed is a sequence of events. This is the post-hoc fallacy.

Malcolm Gladwell’s “law of the few,” discussed in the last chapter, is a poster child for the post-hoc fallacy. Any time something interesting happens, whether it is a surprise best seller, a breakout artist, or a hit product, it will invariably be the case that someone was buying it or doing it before everyone else, and that person is going to seem influential. The Tipping Point, in fact, is replete with stories about interesting people who seem to have played critical roles in important events: Paul Revere and his famous midnight ride from Boston to Lexington that energized the local militias and triggered the American Revolution. Gaëtan Dugas, the sexually voracious Canadian flight attendant who became known as Patient Zero of the American HIV epidemic. Lois Weisberg, the title character of Gladwell’s earlier New Yorker article, who seems to know everyone, and has a gift for connecting people. And the group of East Village hipsters whose ironic embrace of Hush Puppies shoes preceded a dramatic revival in the brand’s fortunes.

These are all great stories, and it’s hard to read them and not agree with Gladwell that when something happens that is as surprising and dramatic as the Minutemen’s unexpectedly fierce defense of Lexington on April 17, 1775, someone special—someone like Paul Revere—must have helped it along. Gladwell’s explanation is especially convincing because he also relates the story of William Dawes, another rider that night who also tried to alert the local militia, but who rode a different route than Revere. Whereas the locals along Revere’s route turned out in force the next day, the townsfolk in places like Waltham, Massachusetts, which Dawes visited, seemed not to have found out about the British movements until it was too late. Because Revere rode one route and Dawes rode the other, it seems clear that the difference in outcomes can be attributed to differences between the two men. Revere was a connector, and Dawes wasn’t.6

What Gladwell doesn’t consider, however, is that many other factors were also different about the two rides: different routes, different towns, and different people who made different choices about whom to alert once they had heard the news themselves. Paul Revere may well have been as remarkable and charismatic as Gladwell claims, while William Dawes may not have been. But in reality there was so much else going on that night that it’s no more possible to attribute the outcomes the next day to the intrinsic attributes of the two men than it is to attribute the success of the Mona Lisa to its particular features, or the drop in violence in the Sunni Triangle of Iraq in 2008 to the surge. Rather, people like Revere, who after the fact seem to have been influential in causing some dramatic outcome, may instead be more like the “accidental influentials” that Peter Dodds and I found in our simulations—individuals whose apparent role actually depended on a confluence of other factors.

To illustrate how easily