In the great majority of these panics, officials do some calculations and find that the rate of illness can easily be the result of chance alone. This is explained and that’s the end of it. But sometimes—usually when residents who don’t trust the official explanation take their worries to the media and politicians get involved—full-scale investigations are launched. Almost always, nothing is found. Residents and activists have been known to reject even these findings, but their suspicions say far more about the power of Gut-based judgments than they do about cancer.
I don’t want to overstate Gut’s failings. Even in this world of satellites and microchips, intuition still gets many things right. It’s also important to remember that science and statistics have their own limitations. They never fully eliminate uncertainty, for one. Statistics may tell us that an apparent cancer cluster could be a product of chance, but they can’t tell us that it is a product of chance. And even the most thorough epidemiological studies cannot absolutely prove that farmers’ pesticides are or are not causing cancer—they can only suggest it, sometimes weakly, sometimes strongly, but always with some degree of uncertainty. In all forms of scientific inquiry, hard facts and strong explanations are built up slowly, and only with great effort. “Sometimes Gut does get it right, even before science does,” Paul Slovic notes. “Other times Gut’s intuitions turn science on to a problem that needs examining. Often, science’s best answer contains much uncertainty. In such cases, if the benefits are not great and the risks are scary, it may be best to go with Gut.” At least until science tells us more.
It’s also heartening to know there is evidence that we can, with a little effort, make ourselves much less vulnerable to Gut’s weaknesses. In a series of four studies, a team of psychologists led by Ellen Peters, a colleague of Slovic’s at Decision Research, examined whether numeracy makes any difference to the mistakes Gut tends to make. It did, in a big way. The studies repeated several well-known experiments—including some mentioned earlier in this book—but this time participants were also tested to see how skilled they were with numbers and math. The results were unequivocaclass="underline" The more numerate people were, the less likely they were to be tripped up by Gut’s mistakes. It’s not clear whether this effect is the result of a numerate person’s Head being better able to intervene and correct Gut or if numeracy, like golf, is a skill that can be learned by the conscious mind and then transferred, with lots of practice, to the unconscious mind. But in either case, numeracy helps.
Much less encouraging is what Ms. Peters found when she tested the numeracy levels of the people in her experiments. Only 74 percent were able to answer this question correctly: “If Person A’s chance of getting a disease is 1 in 100 in 10 years, and Person B’s risk is double that of Person A, what is B’s risk?” Sixty-one percent got this question right: “Imagine that we roll a fair, six-sided die 1,000 times. Out of 1,000 rolls, how many times do you think the die will come up even (2, 4, or 6)?” And just 46 percent figured out this one: “In the Acme Publishing Sweepstakes, the chance of winning a car is one in 1,000. What percent of tickets of Acme Publishing Sweepstakes win a car?” Peters’s test subjects were university students. When a nation’s university-educated elite has such a weak grasp of the numbers that define risk, that nation is in danger of getting risk very wrong.
The breast-implant panic was at its peak in June 1994, when science finally delivered. A Mayo Clinic epidemiological survey published in the New England Journal of Medicine found no link between silicone implants and connective-tissue disease. More studies followed, all with similar results. Finally, Congress asked the Institute of Medicine (IOM), the medical branch of the National Academy of Sciences, to survey the burgeoning research. In 1999, the IOM issued its report. “Some women with breast implants are indeed very ill and the IOM committee is very sympathetic to their distress,” the report concluded. “However, it can find no evidence that these women are ill because of their implants.”
In June 2004, Dow Corning emerged from nine years of bankruptcy. As part of its reorganization plan, the company created a fund of more than $2 billion in order to pay off more than 360,000 claims. Given the state of the evidence, this might seem like an unfair windfall for women with implants. It was unfair to Dow Corning, certainly, but it was no windfall. Countless women had been tormented for years by the belief that their bodies were contaminated and they could soon sicken and die. In this tragedy, only the lawyers won.
In November 2006, the Food and Drug Administration lifted the ban on silicone breast implants. The devices can rupture and cause pain and inflammation, the FDA noted, but the very substantial evidence to date does not indicate that they pose a risk of disease. Anti-implant activists were furious. They remain certain that silicone breast implants are deadly, and it seems nothing can convince them otherwise.
6
The Herd Senses Danger
You are a bright, promising young professional and you have been chosen to participate in a three-day project at the Institute of Personality Assessment and Research at the University of California in sunny Berkeley. The researchers say they are interested in personality and leadership and so they have brought together an impressive group of one hundred to take a closer look at how exemplary people like you think and act.
A barrage of questions, tests, and experiments follows, including one exercise in which you are asked to sit in a cubicle with an electrical panel. Four other participants sit in identical cubicles next to you, although you cannot see each other. Slides will appear on the panel that will ask you questions, you are told, and you can answer with the switches on the panel. Each of the panels is connected to the others so you can all see one another’s answers, although you cannot discuss them. The order in which you will answer will vary.
The questions are simple enough at first. Geometric shapes appear and you are asked to judge which is larger. At the beginning, you are the first person directed to respond. Then you are asked to be the second to answer, which allows you to see the first person’s response before you give yours. Then you move to the number-three spot. There’s nothing that takes any careful consideration at this point, so things move along quickly.
Finally, you are the last of the group to answer. A slide appears with five lines on it. Which line is longest? It’s obvious the longest is number 4 but you have to wait before you can answer. The first person’s answer pops up on your screen: number 5. That’s odd, you think. You look carefully at the lines. Number 4 is obviously longer than number 5. Then the second answer appears: number 5. And the third answer: number 5. And the fourth: number 5.
Now it’s your turn to answer. What will it be?
You clearly see that everyone is wrong. You shouldn’t hesitate to flip the switch for number 4. And yet there’s a good chance you won’t. When this experiment was conducted by Richard Crutchfield and colleagues in the spring of 1953, fifteen people out of fifty ignored what they saw and went with the consensus.
Crutchfield’s work was a variation on experiments conducted by Solomon Asch in the same era. In one of psychology’s most famous experiments, Asch had people sit together in groups and answer questions that supposedly tested visual perception. Only one person was the actual subject of the experiment, however. All the others were instructed, in the later stages, to give answers that were clearly wrong. In total, the group gave incorrect answers twelve times. Three-quarters of Asch’s test subjects abandoned their own judgment and went with the group at least once. Overall, people conformed to an obviously false group consensus one-third of the time.