WE HAVE all heard of experts who fail basic tests of sensory discrimination in their own field: wine snobs who can't tell red from white wine (albeit in blackened cups), or art critics who see deep meaning in random lines drawn by a computer. We delight in such stories since anyone with pretensions to authority is fair game. But what if we shine the spotlight on choices we make about everyday things? Experts might be forgiven for being wrong about the limits of their skills as experts, but could we be forgiven for being wrong about the limits of our skills as experts on ourselves?

We have been trying to answer this question using techniques from magic performances. Rather than playing tricks with alternatives presented to participants, we surreptitiously altered the outcomes of their choices, and recorded how they react. For example, in an early study we showed our volunteers pairs of pictures of faces and asked them to choose the most attractive. In some trials, immediately after they made their choice, we asked people to explain the reasons behind their choices.

Unknown to them, we sometimes used a double-card magic trick to covertly exchange one face for the other so they ended up with the face they did not choose. Common sense dictates that all of us would notice such a big change in the outcome of a choice. But the result showed that in 75 per cent of the trials our participants were blind to the mismatch, even offering "reasons" for their "choice".

We called this effect "choice blindness", echoing change blindness, the phenomenon identified by psychologists where a remarkably large number of people fail to spot a major change in their environment. Recall the famous experiments where X asks Y for directions; while Y is struggling to help, X is switched for Z - and Y fails to notice. Researchers are still pondering the full implications, but it does show how little information we use in daily life, and undercuts the idea we know what is going on around us.

When we set out, we aimed to weigh in on the enduring, complicated debate about self-knowledge and intentionality. For all the intimate familiarity we feel we have with decision-making, it is very difficult to know about it from the "inside": one of the great barriers for scientific research is the nature of subjectivity.

As anyone who has ever been in a verbal disagreement can attest, people tend to give elaborate justifications for their decisions, which we have every reason to believe are nothing more than rationalisations after the event. To prove such people wrong, though, or even provide enough evidence to change their mind, is an entirely different matter: who are you to say what my reasons are?

But with choice blindness we drive a large wedge between intentions and actions in the mind. As our participants give us verbal explanations about choices they never made, we can show them beyond doubt - and prove it - that what they say cannot be true. So our experiments offer a unique window into confabulation (the story-telling we do to justify things after the fact) that is otherwise very difficult to come by. We can compare everyday explanations with those under lab conditions, looking for such things as the amount of detail in descriptions, how coherent the narrative is, the emotional tone, or even the timing or flow of the speech. Then we can create a theoretical framework to analyse any kind of exchange.
Choice blindness drives a wedge between intentions and actions in the mind

This framework could provide a clinical use for choice blindness: for example, two of our ongoing studies examine how malingering might develop into true symptoms, and how confabulation might play a role in obsessive-compulsive disorder.

Importantly, the effects of choice blindness go beyond snap judgements. Depending on what our volunteers say in response to the mismatched outcomes of choices (whether they give short or long explanations, give numerical rating or labelling, and so on) we found this interaction could change their future preferences to the extent that they come to prefer the previously rejected alternative. This gives us a rare glimpse into the complicated dynamics of self-feedback ("I chose this, I publicly said so, therefore I must like it"), which we suspect lies behind the formation of many everyday preferences.

We also want to explore the boundaries of choice blindness. Of course, it will be limited by choices we know to be of great importance in everyday life. Which bride or bridegroom would fail to notice if someone switched their partner at the altar through amazing sleight of hand? Yet there is ample territory between the preposterous idea of spouse-swapping, and the results of our early face experiments.

For example, in one recent study we invited supermarket customers to choose between two paired varieties of jam and tea. In order to switch each participant's choice without them noticing, we created two sets of "magical" jars, with lids at both ends and a divider inside. The jars looked normal, but were designed to hold one variety of jam or tea at each end, and could easily be flipped over.

Immediately after the participants chose, we asked them to taste their choice again and tell us verbally why they made that choice. Before they did, we turned over the sample containers, so the tasters were given the opposite of what they had intended in their selection. Strikingly, people detected no more than a third of all these trick trials. Even when we switched such remarkably different flavours as spicy cinnamon and apple for bitter grapefruit jam, the participants spotted less than half of all switches.

We have also documented this kind of effect when we simulate online shopping for consumer products such as laptops or cellphones, and even apartments. Our latest tests are exploring moral and political decisions, a domain where reflection and deliberation are supposed to play a central role, but which we believe is perfectly suited to investigating using choice blindness.

Throughout our experiments, as well as registering whether our volunteers noticed that they had been presented with the alternative they did not choose, we also quizzed them about their beliefs about their decision processes. How did they think they would feel if they had been exposed to a study like ours? Did they think they would have noticed the switches? Consistently, between 80 and 90 per cent of people said that they believed they would have noticed something was wrong.

Imagine their surprise, even disbelief, when we debriefed them about the nature of the experiments. In everyday decision-making we do see ourselves as connoisseurs of our selves, but like the wine buff or art critic, we often overstate what we know. The good news is that this form of decision snobbery should not be too difficult to treat. Indeed, after reading this article you might already be cured.

我們都聽說過這樣的故事，專家們沒能通過在他們自己領域的基本感官鑒別測試：葡萄酒專家沒能區(qū)分出是紅葡萄酒還是白葡萄酒（裝在深色杯子里），文學批評家 從計算機隨機生成的文本中讀出了深意。我們喜歡這樣的故事，因為自命權威的人就該是被嘲弄的對象。但仔細看看我們在日常生活中所做的選擇，結果又如何呢？ 專家所犯的錯誤可以因為他們專家能力上的局限而被原諒，但如果我們因為我們對自己的了解不足而犯了錯誤，我們可以被原諒嗎？

我們一直在進行研究，試圖回答這個問題，在研究中我們使用了魔術的技巧。我們沒有在提供給參與者的選擇對象上做手腳，但我們偷偷地篡改了他們的選擇結果，然后記錄他們的反應。例如，在一項早期的研究中，我們給志愿者提供兩張人臉圖片，要求他們選擇最有吸引力的一張。在某些實驗中，當他們做出選擇后，我們馬上要求他們解釋做出選擇的理由。

在受試者不知情的情況下，我們有時會使用魔術中的雙卡片技巧悄悄地交換兩張臉，這樣他們看到的就是他們沒選擇的那張。常識告訴我們，我們都會注意到選擇結果的這種巨大變化，但事實上在75%的實驗中受試者沒有注意到結果與他們的選擇不匹配，甚至還為他們的“選擇”提供了“理由”。

我們把這種現(xiàn)象稱為“選擇的盲點”（choice blindness），與“變化的盲點”（change blindness）相對應。后者是心理學家確認到的一個現(xiàn)象，指相當數(shù)量的人未能指出他們所在的環(huán)境中所發(fā)生的某個大的變化?；叵胍幌履莻€著名的實驗，某人X向Y問路，Y 拼命在考慮該如何回答，甚至于當 X 被換成了另一個人 Z，Y都沒能注意到。研究人員仍然在思考這個實驗的全部含義，但它的確顯示出在日常生活中我們只使用多么少的信息，同時也削弱了這種看法：我們了解周圍所發(fā)生的事。

當我們決定進行這項研究的時候，我們的目標是加入到這個關于自我知識和意向性的持續(xù)、復雜的爭論中。盡管我們感到非常熟悉決策的感覺，從“內(nèi)部”去了解它卻極其困難：對此進行科學研究的一個巨大障礙就是它的主觀性。

每個和別人進行過爭論的人都知道，人們傾向于極力證明他們所做的決定的正當性，即使旁人有充分理由相信那不過是事后的文過飾非。然而，證明這樣的人錯了，或者提供足夠的證據(jù)讓他們改變想法，可就完全是另一回事了：你憑什么說我的理由如何如何呢？

但是，有了“選擇的盲點”，我們就在頭腦中的意愿和行動之間撕開了一道裂縫。當我們的受試者對他們從沒做過的決定給出解釋的時候，我們能夠確鑿地向他們展示、證明他們說的不對。因此，我們的實驗為觀察“虛構理由”（指人們在事后虛構理由為自己的決定辯護的行為）提供了一個獨特的窗口，而這是用其他方法難以得到的。我們可以把日常生活中的那些自我辯解與實驗室條件下的相比較，看看描述中的細節(jié)數(shù)量，引述內(nèi)容的一致性，情感的語調(diào)，甚至話語的時機與流暢程度等等，那樣我們就可以創(chuàng)建一個理論的架構，以分析任何種類的不同點。

這個架構可以將“選擇的盲點”應用于診療：例如，我們正在進行的兩項研究調(diào)查，何以“裝病”有時會發(fā)展為真病，以及“虛構理由”在強迫癥中扮演了何種角色。

就重要性而言，“選擇的盲點” 的效應遠不止做出匆忙的判斷。通過觀察志愿者對偷換的選擇所給出的解釋（無論他們的解釋是長是短，給出了量化的評分還是只給出分類，等等），我們發(fā)現(xiàn)這種交互會改變他們未來的偏好，甚至到了他們真的開始喜歡原本拒絕的選擇項的程度。這給了我們一個難得的機會，使我們得以看到自我反饋（“我選擇了這個，我宣布了我的選擇，因此我必須喜歡它”）的復雜機制，我們猜測，在許多日常偏好的形成過程中，這種機制都在起作用。

我們還想探索“選擇的盲點”的邊界。當然，它應當不會發(fā)生在那些我們知道對我們的日常生活有重要意義的選擇上。在婚禮的圣壇上，有哪個新娘或者新郎會注意不到，自己的另一半被人調(diào)包了嗎？不過，在我們早期的臉孔實驗結果，與這種荒唐的婚禮調(diào)包計之間，依然存在著廣闊的空間。

例如，在最近的一次研究中，我們邀請了一些超市的消費者在兩對果醬和茶中做出選擇。為了能在被試者不注意的情況下調(diào)包，我們制作了兩套魔術壇，壇子的兩端各有一個蓋子，內(nèi)部有一個隔斷。這些壇子看上去很正常，但在每一端各放了一組果醬和茶，可以很容易地切換這兩組物品。

在受試者做出了選擇以后，我們馬上要求他們再嘗一下他們所選擇的結果，然后告訴我們?yōu)槭裁磿龀鲞@樣的選擇。而在他們再次品嘗之前，我們切換了裝有樣品的容器，因此受試者拿到的正好與他們所做的選擇相反。驚人的是，只有不到三分之一的人發(fā)現(xiàn)了其中的奧妙。即便我們切換的是味道極其不同的品種，例如肉桂蘋果醬和苦味葡萄醬，意識到切換的受試者也不到一半。

我們在模擬的在線購物中也記錄到了這種效應，購物對象包括諸如筆記本電腦和手機這樣的消費型產(chǎn)品，甚至還有公寓住房。我們最近的一些實驗正在探索道德和政治抉擇中的影響，這一領域本來應該是深思熟慮的，但我們相信，這一領域也適合使用“選擇的盲點”進行調(diào)查。

在我們的各個實驗中，除了記錄志愿者是否注意到了我們給他們看的不是他們當初的選擇，我們還會問一些有關他們對自己的決策過程的信心的問題。如果他們在我 們這樣的研究中做一個受試者，他們認為自己會感覺如何？他們認為自己會注意到結果被調(diào)包嗎？80%到90%的人說他們相信自己會注意到有些事情不對勁。

想想看，當我們告訴他們我們的實驗實際是怎么回事的時候，他們有多驚訝，甚至覺得無法相信。在我們的日常決策中，我們的確認為自己充分了解自己的品位，但正象那些葡萄酒鑒定家和文學批評家一樣，我們常常對自己所知做了過高的估計。好消息是，這種自我過高估計不難治療。事實上，讀完這篇文章你的病就已經(jīng)治好了。

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