The Kerry Cascade

How a ’50s psychology experiment can explain the Democratic primaries.

John Kerry, viewed from below, gestures while holding a microphone.
John Kerry in Youngstown, Ohio, in February 2004. Chris Hondros/Getty Images

Barring a miraculous comeback by Sen. John Edwards, Sen. John Kerry will win the Democratic presidential nomination—despite the fact that most Democratic voters know little about him and don’t like him very much. A few weeks before the Iowa caucuses, Kerry’s campaign seemed dead, but then he unexpectedly won Iowa, then New Hampshire, and then primary after primary. How did this happen?

One answer may be found in a series of psychology experiments conducted at Swarthmore College in the 1950s.* Swarthmore social psychologist Solomon Asch showed a room of participants a series of slides displaying sets of vertical lines. Two of these lines were clearly the same length, while the others were obviously very different. The subjects were then given the seemingly trivial task of identifying which pair of lines were the same. But there was a trick: Everyone in the room except for one person had been instructed beforehand to give the same incorrect answer. The real subject of the experiment was the lone unwitting participant, and the real test was of an individual’s ability to disagree with his or her peers.

Asch demonstrated a stunning effect: Faced with a decision that, in isolation, no one would ever get wrong, the unwitting subjects went against the evidence of their own eyes about one-third of the time. In psychology, Asch’s result is famous, yet its implications for what we might call “social decision-making” (decisions that are influenced by the previous decisions of others) are largely unappreciated by the general public, or even researchers who study decision-making. And social decisions are everywhere. From the everyday (choosing a movie or a restaurant) to the profound (choosing a religion or a career), each one of us is influenced consciously and unconsciously by our friends, families, colleagues, and role models in ways that make the boundary between what we decide for ourselves and what others decide for us almost impossible to distinguish.

In many situations, social decision-making isn’t a bad idea at all. After all, the world is a complicated place, and other people often do have information that we lack. So, we can often do reasonably well, or at least no worse than the people we are copying, by letting them do the hard work for us.

But sometimes the people we are copying aren’t working either, and that’s where the problems come in. When everyone is looking to someone else for an opinion—trying, for example, to pick the Democratic candidate they think everyone else will pick—it’s possible that whatever information other people might have gets lost, and instead we get a cascade of imitation that, like a stampeding herd, can start for no apparent reason and subsequently go in any direction with equal likelihood. Stock market bubbles and cultural fads are the examples that most people associate with cascades, because they are generally accepted to represent “irrational” behavior (although, curiously, not to the people who are participating in them—just ask a teenager why she wants to get her navel pierced; she won’t say “because it’s a fad”), but the same dynamics can show up even in the serious business of Democratic primaries.

For example, when New Yorkers go to vote next Tuesday, they cannot help but be influenced by Kerry’s victories in Wisconsin last week. Surely those Wisconsinites knew something, and if so many of them voted for Kerry, then he must be a decent candidate. But the voters in Wisconsin were just as influenced by the decisions of voters from the previous round of primaries, who were in turn influenced by the round before theirs, and so on. Before any given primary, if all previous votes have resulted in an even split among candidates, then the prospect for independent thinking still exists. But as the sequence of primaries progresses, the likelihood of successive even splits rapidly diminishes, and one candidate inevitably starts to look like a winner. At that moment, the cascade starts, and all subsequent votes then become exercises in rubber stamping. The reason why this year is so striking is that because Iowa and New Hampshire voted the same way, the onset of the cascade was immediate. And the result is that less than 1 percent of all voters effectively decided that Kerry was to be the Democratic nominee—the rest of us are just tagging along.

Not surprisingly, many people (pundits especially) are reluctant to concede this point. We think of ourselves as autonomous individuals, each driven by own internal abilities and desires and therefore solely responsible for our own behavior, particularly when it comes to voting. No voter ever admits—even to herself—that she chose Kerry because he won New Hampshire. To acknowledge that our decisions might not, in fact, be ours at all, but instead might be a reflection of what we think everyone else thinks diminishes our sense of individuality. That’s why we prefer to invoke other explanations for why we did whatever we did—Kerry supporters might talk about his “electability,” but they believe the support for him has some other basis, such as foreign-policy experience, than just following the crowd. Even Asch’s unwitting subjects—clear victims of manipulation—when interviewed afterwards gave other rationalizations for their decisions, some of them succumbing to what Asch called a “distortion of perception” in which they perceived the majority as being correct.

In fact, the distortion of perception that Asch observed is a special case of what psychologists call “hindsight bias,” the failure to notice how our opinions change as new information becomes available. In a host of experiments, psychologists describe some event (say, an election among Kerry, Edwards, and Howard Dean)—the outcome of which is unknown to the participants—and reveal the correct outcome (Kerry wins) to half the group. The participants are then asked to estimate the probability of various outcomes, and the informed group is specifically told to ignore the information they have received: that is, “What would you have guessed had you not known Kerry would win?” With incredible consistency, however, the informed people convince themselves that that’s what they would have guessed anyway—that they knew it all along.

So, now we have to listen to anguished Dean supporters and their amused detractors proposing all manner of “explanations,” ranging from the difficulty of controlling a decentralized organization to the infamous Iowa concession speech, of how a campaign that looked so strong could have turned out to be so hopeless.

But maybe the Dean campaign wasn’t hopeless at all. Had Dean won in Iowa (a shift that in terms of overall numbers would have been a statistical blip), he might very well have won in New Hampshire, which would in turn have dramatically improved his chances in the next, much larger round of primaries. So, it’s entirely possible that two successive wins at the start would have put him on the crest of precisely the kind of voting cascade that instead turned against and crushed him. Of course, no one (except possibly Dean himself) believes that events could have worked out that way—not even Dean’s supporters. But all the post-hoc rationalizations that have been offered up by the pundits to explain the unraveling of Dean’s campaign are examples of hindsight bias. Now that we know what happened, it’s “obvious” that Dean was going to lose—we just didn’t know it at the time.

In fact, the combination of cascades and hindsight bias renders much of what passes for “obvious” in this election campaign deeply misleading. Because the cascade is effectively driven by a small minority of voters, the result is more or less arbitrary—Dean really could be winning just as easily as Kerry. But once we know the answer, hindsight bias kicks in and makes the arbitrariness of the cascade (seem to) go away. Everything pundits are saying about Dean now could just as easily be used (and would have been used) to “explain” a Dean victory. Had that happened instead, we would all be walking around saying, “Well, of course Kerry lost—he’s got all the charisma of a dead horse—and that Dean is a real firebrand.” In each of these “parallel worlds,” Dean and Kerry are exactly the same (more or less), and voters are (more or less) exactly the same as well. In terms of the inputs, the difference between the two worlds could be a coin toss. And yet the results, along with our collective memory of what happened and why, are absolutely, completely different, and we can’t even imagine now what that other world would have looked like, let alone how vigorously we’d be rationalizing it.

Correction, Feb. 5, 2020: This article originally misstated where Solomon Asch’s conformity experiments were first conducted. They were done at Swarthmore, not Princeton.