The Undoing Project: A Friendship that Changed the World(42)

In Danny’s view, people were not conservative Bayesians. They were not statisticians of any kind. They often leapt from little information to big conclusions. The theory of the mind as some kind of statistician was of course just a metaphor. But the metaphor, to Danny, felt wrong. “I knew I was a lousy intuitive statistician,” he said. “And I really didn’t think I was stupider than anyone else.”

The psychologists in Ward Edwards’s lab were interesting to Danny in much the same way that the psychoanalysts at the Austen Riggs Center had been interesting to him after their patient had surprised them by killing herself. What interested him was their inability to face the evidence of their own folly. The experiment Amos had described was compelling only to someone already completely sold on the idea that people’s intuitive judgment approximated the correct answer—that they were, at least roughly, good Bayesian statisticians.

Which was odd when you thought about it. Most real-life judgments did not offer probabilities as clean and knowable as the judgment of which book bag contained mostly red poker chips. The most you could hope to show with such experiments is that people were very poor intuitive statisticians—so poor they couldn’t even pick the book bag that offered them the most favorable odds. People who proved to be expert book bag pickers might still stumble when faced with judgments in which the probabilities were far more difficult to know—say, whether some foreign dictator did, or did not, possess weapons of mass destruction. Danny thought, This is what happens when people become attached to a theory. They fit the evidence to the theory rather than the theory to the evidence. They cease to see what’s right under their nose.

Everywhere one turned, one found idiocies that were commonly accepted as truths only because they were embedded in a theory to which the scientists had yoked their careers. “Just think about it,” said Danny. “For decades psychologists thought that behavior is to be explained by learning, and they studied learning by looking at hungry rats learning to run to a goal box in a maze. That was the way it was done. Some people thought it was BS, but they were not smarter or more knowledgeable than the brilliant people who dedicated their career to what we now see as rubbish.”

The people in this new field devoted to human decision making had become similarly blinded by their theory. Conservative Bayesians. The phrase was worse than meaningless. “It suggests people have the correct answer and they adulterate it—not any realistic psychological process that produces the judgments that people make,” said Danny. “What do people actually do in judging these probabilities?” Amos was a psychologist and yet the experiment he had just described, with apparent approval, or at least not obvious skepticism, had in it no psychology at all. “It felt like a math exercise,” said Danny. And so Danny did what every decent citizen of Hebrew University did when he heard something that sounded idiotic: He let Amos have it. “The phrase ‘I pushed him into the wall’ was often used, even for conversations among friends,” explained Danny later. “The idea that everyone is entitled to his/her opinion was a California thing—that’s not how we did things in Jerusalem.”

By the end of the seminar, Danny must have sensed that Amos didn’t particularly want to argue with him anymore. Danny went home and boasted to his wife, Irah, that he had won an argument with a brash younger colleague. Or anyway, that’s how Irah remembered it. “This is, or was, an important aspect of Israeli discussions,” Danny said. “They were competitive.”

In the History of Amos there aren’t a lot of examples of Amos losing an argument, and there are even fewer examples of Amos changing his mind. “You can never say he’s wrong, even if he’s wrong,” said his former student Zur Shapira. It wasn’t that Amos was rigid. In conversation he was freewheeling and fearless and open to new ideas—though perhaps more so if they did not openly conflict with his own. It was more that Amos had been right so often that, in any argument, “Amos is right” had become a useful assumption for all involved, Amos included. When asked for his memories of Amos, the first thing the Nobel Prize–winning Hebrew University economist Robert Aumann recalled was the one time he had surprised Amos with an idea. “I remember him saying, ‘I didn’t think of that,’” said Aumann. “And I remember it because there wasn’t much Amos hadn’t thought of.”

Danny later suspected that Amos actually hadn’t given much thought to the idea of the human mind as some kind of Bayesian statistician—the stuff with the book bags and poker chips wasn’t his line of research. “Amos probably never had a serious discussion with anyone about that paper,” said Danny. “And if he had, no one would have raised deep objections.” People were Bayesian in the same way that people were mathematicians. Most people could work out that seven times eight equals fifty-six: so what if some could not? Whatever errors they made were random. It wasn’t as if the human mind had some other way of doing math that led it to systematic error. If someone had asked Amos, “Do you think people are conservative Bayesians?,” he might have said something like, “Certainly not every person, but as a description of the average person, it will do.”

In the spring of 1969, at least, Amos wasn’t overtly hostile to the reigning theories in social science. Unlike Danny, he wasn’t dismissive of theory. Theories for Amos were like mental pockets or briefcases, places to put the ideas you wanted to keep. Until you could replace a theory with a better theory—a theory that better predicted what actually happened—you didn’t chuck a theory out. Theories ordered knowledge, and allowed for better prediction. The best working theory in social science just then was that people were rational—or, at the very least, decent intuitive statisticians. They were good at interpreting new information, and at judging probabilities. They of course made mistakes, but their mistakes were a product of emotions, and the emotions were random, and so could be safely ignored.