视听｜人们为何会杞人忧天？

媒体常用各种数字来描述风险，然而这种描述是否准确？又是否能够准确反映事情对人的真实影响？人们又该如何更好地评估风险？Gerd Gigerenzer 的视频也许能给你更多启发。

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Why Do People Fear the Wrong Things?

里面一

A new drug reduces the risk of heart attacks by 40%. Shark attacks are up by a factor of 2. Drinking a litre① of soda per day doubles your chance of developing cancer.

① litre /ˈliːtə/ n. A litre is a metric unit of volume that is a thousand cubic centimetres. It is equal to 2.11 pints. 升（公制容量单位）

These are all examples of relative risk; a common way risk is presented in news articles. Risk evaluation is a complicated tangle② of statistical thinking and personal preference. One common stumbling block③ is the difference between relative risks like these and what are called absolute risks.

② tangle /ˈtæŋɡəl/ n. A tangle of something is a mass of it twisted together in a messy way. 乱糟糟的一团

③ stumbling block /ˈstʌmblɪŋ blɒk/ n. A stumbling block is a problem which stops you from achieving something. 绊脚石

Risk is the likelihood that an event will occur. It can be expressed as either a percentage–for example, that heart attacks occur in 11% of men between the ages of 60 and 79–or as a rate–that one in two million divers along Australia’s western coast will suffer a fatal shark bite each year. 

These numbers express the absolute risk of heart attacks and shark attacks in these groups. Changes in risk can be expressed in relative or absolute terms. For example, a review in 2009 found that mammography④ screenings reduced the number of breast cancer deaths from five women in one thousand to four. The absolute risk reduction was about .1%. But the relative risk reduction from 5 cases of cancer mortality to four is 20%. Based on reports of this higher number, people overestimated the impact of screening.

④ mammography /mæˈmɒɡrəfɪ/ n. Mammography is the use of X-rays to examine women's breasts in order to detect cancer. 乳房X线摄影术

To see why the difference between the two ways of expressing risk matters, let’s consider the hypothetical⑤ example of a drug that reduces heart attack risk by 40%. Imagine that out of a group of 1000 people who didn’t take the new drug, 10 would have heart attacks. The absolute risk is 10 out of 1000, or 1%. If a similar group of 1000 people did take the drug, the number of heart attacks would be six. In other words, the drug could prevent four out of ten heart attacks–a relative risk reduction of 40%. Meanwhile, the absolute risk only dropped from 1% to 0.6%–but the 40% relative risk decrease sounds a lot more significant.

⑤ hypothetical /ˌhaɪpəˈθɛtɪkəl/ adj. If something is hypothetical, it is based on possible ideas or situations rather than actual ones. 假设的

Surely preventing even a handful of heart attacks, or any other negative outcome, is worthwhile–isn’t it? Not necessarily. The problem is that choices that reduce some risks can put you in the path of others. Suppose the heart-attack drug caused cancer in one half of 1% of patients. In our group of 1000 people, four heart attacks would be prevented by taking the drug, but there would be five new cases of cancer. The relative reduction in heart attack risk sounds substantial⑥ and the absolute risk of cancer sounds small, but they work out to about the same number of cases.

⑥ substantial /səbˈstænʃəl/ adj. Substantial means large in amount or degree. 大量的; 很大程度的

In real life, everyone’s individual evaluation of risk will vary depending on their personal circumstances. If you know you have a family history of heart disease you might be more strongly motivated to take a medication⑦ that would lower your heart-attack risk, even knowing it provided only a small reduction in absolute risk.

⑦ medication /ˌmɛdɪˈkeɪʃən/ n. Medication is medicine that is used to treat and cure illness. 药物

Sometimes, we have to decide between exposing ourselves to risks that aren’t directly comparable. If, for example, the heart attack drug carried a higher risk of a debilitating⑧, but not life-threatening, side effect like migraines⑨ rather than cancer, our evaluation of whether that risk is worth taking might change. And sometimes there isn’t necessarily a correct choice: some might say even a minuscule⑩ risk of shark attack is worth avoiding, because all you’d miss out on is an ocean swim, while others wouldn’t even consider skipping a swim to avoid an objectively tiny risk of shark attack. 

⑧ debilitate /dɪˈbɪlɪˌteɪt/ v. If you are debilitated by something such as an illness, it causes your body or mind to become gradually weaker. 虚弱

⑨ migraine /ˈmiːɡreɪn/ n. A migraine is an extremely painful headache that makes you feel very ill. 偏头痛

⑩ minuscule /ˈmɪnəˌskjuːl/ adj. If you describe something as minuscule, you mean that it is very small. 极小的

For all these reasons, risk evaluation is tricky at baseline, and reporting on risk can be misleading, especially when it shares some numbers in absolute terms and others in relative terms. Understanding how these measures work will help you cut through some of the confusion and better evaluate risk.

文章来源：TED-Ed官网

大连外国语大学高级翻译学院实习生

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