羣體智慧成了陳詞濫調

The wisdom of crowds” has become a modern cliché. And a strange one — the crowds that attended the Nuremberg Rallies, or cheered the tumbrils of the Reign of Terror, were anything but wise. Many adjectives might be applied to the assemblies that gather to applaud Dear Leader Kim Jong Un or cheer ChelSea Football Club — but “wise” is not one. Anyone standing back from these events must ask themselves a question: how could large numbers of people, so similar to ourselves, behave like that? What on earth were they thinking?

“羣體的智慧”已變成了一個現代陳詞濫調。它也是一種奇怪的說法——那些參加紐倫堡黨代會（Nuremberg Rallies，1923至1938年期間納粹黨一年一度的集會——譯者注）的人、“雅各賓專政”(Reign of Terror)時期那些在囚車旁歡呼的人，都根本毫無判斷力。許多形容詞可能都適用於描述一羣聚集在一起、爲“親愛的領袖”金正恩(Kim Jong Un)鼓掌或是爲切爾西足球俱樂部(Chelsea Football Club)歡呼的人，但“有判斷力”絕非其中之一。任何未參加過這些活動的人都必須問自己一個問題：爲何這麼多和我們如此相像的人會有那樣的表現？他們究竟在想什麼？

There is considerable research on the factors that influence the behaviour of crowds. We experience a need to affirm group or tribal identities — a fact that is often exploited by unscrupulous or mentally unbalanced leaders. Groups of people with similar opinions reinforce each other’s positions, encouraging one another to adopt ever moreextreme views. The answer to the question “what were they thinking?” is that, mostly, they were not thinking at all. That is often the nature of social behaviour.

關於影響羣體行爲的因素，有相當多的研究。我們有確認自己羣體或部落身份的現實需求，但這一點經常被不擇手段或精神有問題的領導人所利用。擁有相似觀點的羣體成員會強化彼此的觀點，促使彼此的觀點更加極端化。“他們在想什麼？”——這個問題的答案是：大多數時候，他們根本沒有在思考。這通常就是羣體行爲的本質。

So how did the phrase “wisdom of crowds” come into being? It is an expression of the mathematical property that an average of many independent estimates of the same variable has a lower expected error than the individual estimates themselves. That was the context of the example which James Surowecki used to introduce the idea in his widely read book of the same name, citing the distinguished mathematician Francis Galton’s observations at an ox weighing competition (actually, Galton was concerned with the median rather than the mean estimate, but let that technical detail pass).

那麼，“羣體的智慧”這一說法又是如何產生的呢？它表達的其實是一種數學特性，即對同一變量的許多獨立判斷的平均值比個人自己判斷的預期錯誤率要低。這就是詹姆斯•蘇羅維奇(James Surowecki)在他那本廣爲傳閱的同名書《羣體的智慧》(wisdom of crowds)中所援引那個例子的背景。蘇羅維奇援引的是著名數學家弗朗西斯•高爾頓(Francis Galton)對一場猜測一頭公牛重量比賽的觀察（實際上，高爾頓關注的是中位數而非平均估值，但這裏忽略這一技術細節），從而提出了羣體有智慧的觀點。

It is entirely rational to adopt the common opinion on a subject about which one knows little; I believe the earth is round because that is the balance of informed opinion, and would a millennium ago have believed it to be flat, for the same reason. But the number of practical situations in which this statistical property is useful is severely limited. It is usually better to direct one’s efforts at reducing the error of estimates rather than increasing the number of erroneous estimates. That is why we prefer to entrust the navigation of a plane to a skilled pilot instead of using the average of the opinions of the passengers.

在一個自己不甚瞭解的問題上接受公認的看法是完全明智的；我相信地球是圓的，因爲這一結論是主流權威觀點，而出於同樣的原因，1000年前的人們曾經相信它是平的。但能讓這種統計特性能發揮作用的現實情形是非常有限的。通常情況下，更好的辦法是去努力減少估計中的錯誤，而非增加錯誤估計的數量。這就是爲什麼我們更願意將開飛機的任務託付給熟練的飛行員，而不是綜合採納大多數乘客的意見。

The wisdom of crowds becomes a pathology when the estimates of the members of the crowd cease to be independent of each other, and this is likely when the crowd is large, ill-informed, or both. It is in the nature of a crowd to turn on anyone who dissents from what is already the average opinion. This is equally true on the streets of revolutionary Paris, the squares of Pyongyang, and the terraces of Chelsea Football Club.

當每個羣體成員的判斷不再是相互獨立的，羣體的智慧就會變得病態。當羣體數量龐大、信息不靈通（或兩者兼有)時，這種情況更可能出現。羣體的本性決定了，任何與既有主流觀點意見相左的人都會受到羣體的攻擊。在大革命時期的巴黎街頭、在平壤的廣場上，以及在切爾西俱樂部的看臺上，情況都是如此。

Or on the trading floor of an investment bank. The supposed wisdom of crowds is used as a justification for claims of market efficiency, crudely expressed in slogans such as “the market knows best” and “you can’t buck the market”. At a sophisticated level, the idea provides a rationale for a regulatory philosophy that attempts to reproduce the conditions required for the validity of Galton’s result — the existence of many independent estimates of the same variable.

這種情形同樣適用於投資銀行的交易大廳。所謂羣體有智慧的觀點被當作支持市場有效論的理由，並被簡單地總結爲“市場最權威”和“你不能逆市而爲”等口號。說得複雜一點，羣體有智慧的觀點則爲一種監管理念提供了理由，這種理念試圖複製證實高爾頓觀察結果（即存在對同一變量的許多種獨立估算）所必需的條件。

So we aim to promote a trading environment characterised by many conflicting assessments of the value of a security based on identical — and therefore necessarily limited — information about the value of securities. The belief that an aggregate of casual opinions provides a better process of value discovery than a flow of informed judgment through close engagement by investors, is an article of faith rather than a matter of empirical evidence.

因此，我們的目標是推動這樣一種交易環境，它的特點是，基於相同（因此也是有限的）信息，對一支證券的價值存在許多種不一致的評估。有人認爲，與投資者通過密切關注而產生的大量明智判斷相比，隨機觀點的彙總能更好地發現價值，這種看法只是一種信念，缺乏經驗證據的支持。

Galton wrote of the wisdom of crowds. The still more distinguished mathematician Isaac Newton, after losing vast sums investing in the South Sea bubble, wrote more wisely of their madness.

高爾頓描寫了羣體的智慧。一位更著名的數學家艾薩克•牛頓(Isaac Newton)在南海股票泡沫中損失大筆資金之後，更明智地描繪了他們的瘋狂。