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Economics is a notoriously imperialist discipline: economists are more prone to colonising other scholarly fields than to be colonised by them. The single biggest exception was Daniel Kahneman, the social psychologist who was awarded the 2002 Nobel Memorial prize in economic science for how he revolutionised the field.
經濟學是一門以帝國主義著稱的學科：經濟學家更傾向於對其他學術領域進行「殖民」，而非被它們「殖民」。然而，社會心理學家丹尼爾•卡尼曼(Daniel Kahneman)是一個顯著的例外，他因爲對經濟學領域的革命性改變而榮獲2002年的諾貝爾經濟學獎。
It was in the 1970s and early 1980s that Kahneman, who has died aged 90, carried out the path-breaking research in the psychology of decision-making that would upend economics, much of it with his collaborator Amos Tversky (who died in 1996). They showed that humans faced with uncertain situations tend to make judgments and take decisions based on systematic biases. People rely as much on flimsy as on solid evidence of what the probable outcomes are; they are guided less by probabilities than by how closely a situation represents preconceived ideas; they care about changes rather than absolute levels of, for example, wealth, and care more about losses than they do equally sized gains; they also have a propensity to stick with the status quo.
卡尼曼在1970年代和1980年代初進行了開創性的決策心理學研究，這些研究顛覆了經濟學，大部分研究是與他的合作者阿莫斯•特沃斯基(Amos Tversky)共同完成的。他們揭示了人們在面對不確定情況時，往往會基於系統性偏見做出判斷和決策。人們在預測可能的結果時，既依賴不穩定的證據，也依賴堅實的證據；他們的決策更多地受到先入爲主的觀念的影響，而非機率；他們更關心變化，而非例如財富的絕對水準，對損失的關注度超過同等大小的收益；他們也有保持現狀的傾向。
These are just some of the patterns Kahneman and Tversky documented, several of which they incorporated into “prospect theory”, their model of how people make choices in the face of risk and uncertainty. This flew in the face of the theory of rational decision-making that was fundamental to economics. Kahneman later reminisced that they had not set out to challenge economists’ concept of rationality. “I realised only recently how fortunate we were not to have aimed deliberately at the large target we happened to hit. If we had intended [an influential 1974 article in Science] as a challenge to the rational model, we would have written it differently, and the challenge would have been less effective.”
這些只是卡尼曼和特沃斯基所記錄的一些模式，他們將其中幾個納入了他們的「前景理論」，這是他們研究人們在面對風險和不確定性時如何做出選擇的模型。這與經濟學基礎的理性決策理論形成了鮮明對比。卡尼曼後來回憶說，他們並沒有打算挑戰經濟學家的理性概念。「我直到最近才意識到，我們是多麼幸運，沒有刻意瞄準我們碰巧擊中的大目標。如果我們把[1974年發表在《科學》上的一篇頗具影響力的文章]作爲對理性模型的挑戰，我們就會以不同的方式來寫，而挑戰的效果也會大打折扣。」
Effective it certainly was. Kahneman and Tversky’s work caught the eye of Richard Thaler, then a young economist with a sceptical eye on his own field, who was the first to incorporate their insights into economic modelling. This quickly caught on, as their work helped explain behaviour that did not fit economists’ standard theory of consumer choice. In the ensuing decades, psychological biases were documented and used to explain a variety of economic topics, from consumer behaviour to development, to labour markets and financial market anomalies. The field of behavioural economics was born.
這確實非常有效。卡尼曼和特沃斯基的研究引起了理查德•塞勒(Richard Thaler)的關注，當時他還是一位對自己的領域持有懷疑態度的年輕經濟學家，他是第一個將他們的洞見融入經濟模型的人。這種理論很快得到了廣泛的接受，因爲他們的工作有助於解釋那些不符合經濟學家的標準消費者選擇理論的行爲。在接下來的幾十年裏，心理偏差被詳細記錄，並被用來解釋各種經濟主題，從消費者行爲到發展，再到勞動力市場和金融市場的異常現象。行爲經濟學領域因此而誕生。
Kahneman and Tversky were “the founders of our field”, says Ulrike Malmendier, a behavioural economist at the University of California, Berkeley. Its success, she says, has been “overwhelming”. Malmendier, a member of the German official council of economic experts, points out that not only has the behavioural approach gained acceptance throughout most of economics, it is also appreciated by policymakers.
加利福尼亞大學伯克利分校的行爲經濟學家烏爾麗克•馬爾門迪爾(Ulrike Malmendier)稱，卡尼曼和特沃斯基是「我們領域的創辦人」。她認爲，這個領域的成功是「壓倒性的」。作爲德國官方經濟專家委員會的成員，馬爾門迪爾指出，行爲經濟學不僅在大部分經濟學領域得到了認可，政策制定者也對其表示讚賞。
“Whenever I’m talking with the highest level of politicians, I can be sure to get a question asking ‘well, you as a behavioural economist, how would you think about such-and-such?’ People are aware that we have other tools than standard carrot-and-stick economic incentives.”
「每當我與最高級別的政治家交談時，我總會被問到『作爲一名行爲經濟學家，你對某某問題有何看法？』人們明白，我們除了標準的獎懲經濟激勵手段外，還有其他工具可用。」
This interest can in part be credited to Kahneman himself, who popularised his research in the 2011 book Thinking, Fast and Slow. Yet he remained slightly bemused at the influence his work ended up having. When he received the Nobel Prize, he remarked that “I have been mostly cheering Thaler and behavioural economics from the sidelines”. The paper on prospect theory, he said, was influential only because it was published in the highly prestigious journal Econometrica — “What impresses me is how chancy this is, that is this is entirely accidental . . . if we’d published that word for word [elsewhere] there would have been no Nobel Prize for this work today.”
這種興趣可以部分歸功於卡尼曼本人，他在2011年出版的《思考，快與慢》一書中普及了他的研究。然而，他對自己的研究成果產生的影響仍然感到有些困惑。當他獲得諾貝爾獎時，他說：「我主要是在場邊爲塞勒和行爲經濟學喝彩。」他說，關於前景理論的論文之所以有影響力，只是因爲它發表在極具聲望的《計量經濟學》雜誌上——「讓我印象深刻的是，這是多麼的偶然，這完全是偶然的……如果我們一字不差地在其他地方發表，今天就不會有這項工作的諾貝爾獎了。」
Those who knew Kahneman stress his unfailing interest in what other people thought. Younger scholars praise his lack of defensiveness about his work, and his eagerness to see it overtaken by new research. His list of co-authors is a who’s who of economics and other fields. He once told the FT that “everything I’ve done has been collaborative.”
瞭解卡尼曼的人都強調他對他人想法的持續興趣。年輕的學者們讚揚他對自己的工作沒有防禦性，並且渴望看到新的研究超越他的工作。他的合著者名單是經濟學和其他領域的名人錄。他曾經告訴英國《金融時報》：「我所做的一切都是合作的。」
Kahneman was born in Tel Aviv and was based in Israel during the postwar decades before moving to the US later on. But he spent his childhood in Paris and Nazi-occupied France. He was seven or eight when he walked home from a friend after the curfew imposed on Jews and encountered an SS man. Despite young Daniel’s fear that his hidden yellow star would show, the Nazi lifted him up to hug him, then emotionally showed him a photo of a boy, and gave him some money. “I went home more certain than ever that my mother was right: people were endlessly complicated and interesting.” Martin Sandbu
卡尼曼出生於特拉維夫(Tel Aviv)，戰後的幾十年裏一直在以色列工作，後來移居美國。然而，他的童年是在巴黎和納粹佔領的法國度過的。在對猶太人實施宵禁後，他從朋友那裏走回家，那時他只有七八歲，卻遇到了一名黨衛軍。儘管小丹尼爾擔心他隱藏的黃星會被發現，但納粹還是把他抱了起來，然後動情地給他看了一張男孩的照片，並給了他一些錢。「回家後，我比以往任何時候都更加確信母親是對的：人是無盡複雜而有趣的。」馬丁•桑德布(Martin Sandbu)