2020考研英語閱讀理解精讀100篇：Unit 57

Unit 57

Past performance is not an indicator of future returns. That, at least, is the advice given to investors. But can the likelihood of a person committing a crime be predicted by looking at his record? The answer, according to a team of clinical forensic psychologists, is that it cannot. Not only is risk prediction unreliable but, when applied to individuals rather than groups, the margins of error are so high as to render any result meaningless.

Making assumptions about individuals from group data is generally only reasonably safe when the variation within the group is small. Despite this, risk assessments are routinely used to help decide who should be locked up, who should undergo therapy and who should go free. Risk prediction is also set to be used to assess the threat posed by people ranging from terrorist suspects to potential delinquents.

Stephen Hart, of Simon Fraser University in British Columbia, Canada, and colleagues decided to determine how accurate the tests of risk assessment are when applied to individuals rather than groups. Typically the tests work by assigning a score to people depending on factors such as their age, the history of their relationships, their criminal past and the type of victims they have chosen. If someone’s score places him in a group in which a known proportion has gone on to commit a crime on release from detention, then the risk that person will prove a recidivist is thought to be similar to the risk for the group as a whole.

The paper published by Dr Hart and his colleagues in last month’s issue of the British Journal of Psychiatry focused on two popular tests that follow this logic. The first was a 12-item test designed to assess risk for general violence over periods of seven to ten years. The second was a ten-item test designed to assess risk for violence and sexual violence over periods of five to 15 years. The researchers have also assessed other tests used for predicting sexual offences and domestic violence.

They found that variations between members of the groups were very large. In one of the tests, for example, the standard estimate of the chances of members of the group sexually reoffending was put at 36% within 15 years. They calculated that the actual range was between 30% and 43% of the group, with a 95% confidence level. But calculating the average probability for a group is much easier than calculating the same probability for any individual. Thus, using standard methods to move from group inferences to individual ones, they calculated that the chance of any one person reoffending was in the range of 3% to 91%, similarly with a 95% confidence level. Clearly, the seemingly precise initial figure is misleading.

The principle is not peculiar to psychology. It has been recognised by statisticians for decades. They call it the ecological fallacy（although this term captures broader subtleties, too）. Medicine has also been confounded by statistically based procedures. Indeed, the technique is only really useful when the successes and failures are aggregated. A life-insurance company, for instance, could wrongly predict the life span of every person it insured but still get the correct result for the group.

注（1）：本文選自Economist；

注（2）：本文習題命題模仿對象為2004年真題Text 4。

1. What do the clinical forensic psychologists think of risk prediction?

A) Risk prediction fails in the stock market but succeeds in predicting crime probability.

B) Risk prediction is always effective when being applied to groups.

C) Risk prediction is not dependable when it comes to individual behavior.

D) Risk prediction of groups lacks reliability because of high margin error.

2. We can learn from the text that tests of risk assessment are _______.

A) longitudinal

B) very tricky

C) convincing enough

D) unreasonable

3. What premise did Dr Hart follow when conducting his research?

A) Two groups should be designed for the tests, with one test group and the other for comparison.

B) Both risk assessment and risk prediction should be considered in the tests.

C) People selected for the tests should vary greatly from each other so as to guarantee the representativeness of the sample.

D) Given small variation within a group, risk prediction for individuals can be based on group data.

4. According to Dr Hart, using standard methods to predict individuals _______.

A) is as easy as using them for groups

B) yields ineffective statistics

C) can help attain precise results

D) might be influenced by confidence level

5. Which of the following statements is TRUE?

A) Ecological fallacy is originally a psychological phenomenon, which is later adopted in the field of statistics.

B) Statisticians have been dealing with ecological fallacy for a long time and have almost succeeded in figuring out a solution.

C) The statistics from a life insurance company on the longevity of a group of people should be reliable.

D) Risk prediction proves to be of zero practical value according to Dr Hart’s study.

篇章剖析

本文主要就風險預測的話題展開論述。第一段首先提出了風險預測站不住腳；第二段指出，只有當一組數據內部差異程度相對較小時，對個人的判斷才可能更可靠；第三、四段主要介紹了哈特博士針對以上問題進行的實驗；第五段介紹了實驗結果，說明了針對個人進行的風險預測有很大的誤導性；第六段則進一步對風險預測的負面作用加以延伸，并以一個開放性的建議結束全文。

詞匯注釋

margin /?mɑ?d??n/ n. 差數：頁邊的空白

assessment /??sesm?nt/ n. 評估，估價

routinely /ru??ti?nli/ adv. 例行地；常規地

therapy /?θer?pi/ n. 治療

delinquent /d??l??kw?nt/ n. 失職者，違法者

proportion /pr??p????n/ n. 比例，均衡

detention /d??ten??n/ n. 拘留，禁閉

psychiatry /sa??ka??tri/ n. 精神病學，精神病治療法

domestic /d??mest?k/ adj. 家庭的，國內的

confidence level 置信度

probability /?pr?b??b?l?ti/ n. 概率

inference /??nf?r?ns/ n. 推論

initial /??n???l/ adj. 最初的，初始的

fallacy /?f?l?si/ n. 謬誤，謬論

confound /k?n?fa?nd/ vt. 使混淆，挫敗

aggregate /??ɡr?ɡe?t/ v. 聚集，合計

insure /?n????/ vt. 給…保險

難句突破

If someone’s score places him in a group in which a known proportion has gone on to commit a crime on release from detention, then the risk that person will prove a recidivist is thought to be similar to the risk for the group as a whole.

主體句式：If someone’s score places him in a group... then the risk is thought to be similar to...

結構分析：這個句子分為逗號前后的兩個部分，其中的每一個部分包含一個定語從句。前半個句子中，in which引導的定語從句修飾group；而后半句中，that person will prove a recidivist作為同位語從句修飾risk。

句子譯文：如果一個人的分數屬于出獄后犯罪率很高的一組，那么此人是慣犯的幾率就大體上和這組的整體幾率相同。

題目分析

1. C 細節題。根據文章第一、二段的內容，風險預測對于個人的預測錯誤率極大，幾乎完全不可靠。選項B錯誤的原因在于文章里面沒有直接說明風險預測是否對于群組人有效。

2. A 推理題。文章第四段中舉了兩個測試的具體情況，這兩個測試分別進行了7到10年和5到15年，因此都是長達多年的跟蹤性試驗。A選項longitudinal的意思為“長度的；縱長的”，可以引申為長時間的。

3. D 細節題。文章第四段第一句話指出哈特博士的實驗“follow this logic”，“this logic”指的正是第三段最后一句話，即“如果一個人的分數屬于出獄后犯罪率很高的一組，那么此人是慣犯的幾率就大體上和這組的整體幾率相同”，也就是說，如果組內差異較小的話，關于組的風險預測可以推及到組內的個人。

4. B 細節題。根據文章第五段，如果將群體的標準方法用于個體，最終得到的結果是具有誤導性的。D選項提到的confidence level“置信度”是一個統計上的參數，與本題并無關聯。

5. C 細節題。C選項的信息來自文章的最后一句話，A life-insurance company, for instance, could wrongly predict the life span of every person it insured but still get the correct result for the group，即“例如，一個人壽保險公司也許不能準確預測每個投保人的壽命長度，但它可以對群體做出準確預測?！?

參考譯文

過去的付出并不代表未來的收獲，這至少可以給投資者一些啟示。但一個人的犯罪動機能通過他過去的記錄來預測嗎？一個臨床法醫心理學家小組的回答是否定的。風險預測不僅站不住腳，而且即使是只用于個體而不是群體，其誤差之大也會導致結果失去意義。

只有當一組數據內部差異程度相對較小時，據此做出的對個體的判斷通常才會比較可靠。盡管如此，人們還是例行公事地用風險評估來輔助決定誰應該坐牢、誰應該接受治療以及誰可獲得自由。風險預測同樣用于評估從嫌疑恐怖分子到潛在罪犯的各種威脅。

加拿大不列顛哥倫比亞省西蒙弗雷澤大學的斯蒂芬·哈特和他的同事決意要找出用于個體而非群體的風險評估測試的準確性到底有多大。這些測試先根據個人年齡、社交經歷、犯罪史以及所選擇的受害者類型等因素給人們打出一個分數。如果一個人的分數屬于出獄后犯罪率很高的一組，那么此人是慣犯的幾率就大體上和這組的整體幾率相同。

哈特博士和他的同事在上月的《英國精神病學雜志》上發表了一篇論文，主要介紹了按照這一邏輯進行的兩個有名實驗。第一個實驗包括12項內容的測試，用來評估7至10年間的一般暴力風險；第二個實驗包括10項相關內容的測試，用來評估5至15年間的暴力和性暴力風險。研究人員也評估了用來預測性侵犯和家庭暴力的其他一些測試。

他們發現每組成員間的差別很大。比如在其中一項測試中，被測小組成員15年內再次進行性侵犯的概率估計是36%。在95%的置信度下，他們計算出的實際范圍是在30%與43%之間。但計算群體的平均概率要比計算個體的概率容易得多。因此，如果將群體的標準方法用于個體，同樣在95%的置信度下，他們計算出一個人是慣犯的幾率在3%與91%之間。很明顯，看似準確的原始數據有很大的誤導性。

這個原理不僅專用于心理學，也已被統計學家認可了數十年之久。他們稱其為生態學謬論（盡管這個術語還有更廣泛和精細的意義）。醫學也被基于統計學的程序搞得一團糟。實際上，這個技術只有在成功和失敗都綜合起來的時候才真正有用。例如，一個人壽保險公司也許不能準確預測每個投保人的壽命長度，但它可以對群體做出準確預測。