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.

我们都听说过这样的故事，专家们没能通过在他们自己领域的基本感官鉴别测试：葡萄酒专家没能区分出是红葡萄酒还是白葡萄酒（装在深色杯子里），文学批评家 从计算机随机生成的文本中读出了深意。我们喜欢这样的故事，因为自命权威的人就该是被嘲弄的对象。但仔细看看我们在日常生活中所做的选择，结果又如何呢？ 专家所犯的错误可以因为他们专家能力上的局限而被原谅，但如果我们因为我们对自己的了解不足而犯了错误，我们可以被原谅吗？

我们一直在进行研究，试图回答这个问题，在研究中我们使用了魔术的技巧。我们没有在提供给参与者的选择对象上做手脚，但我们偷偷地篡改了他们的选择结果，然后记录他们的反应。例如，在一项早期的研究中，我们给志愿者提供两张人脸图片，要求他们选择最有吸引力的一张。在某些实验中，当他们做出选择后，我们马上要求他们解释做出选择的理由。

在受试者不知情的情况下，我们有时会使用魔术中的双卡片技巧悄悄地交换两张脸，这样他们看到的就是他们没选择的那张。常识告诉我们，我们都会注意到选择结果的这种巨大变化，但事实上在75%的实验中受试者没有注意到结果与他们的选择不匹配，甚至还为他们的“选择”提供了“理由”。

我们把这种现象称为“选择的盲点”（choice blindness），与“变化的盲点”（change blindness）相对应。后者是心理学家确认到的一个现象，指相当数量的人未能指出他们所在的环境中所发生的某个大的变化。回想一下那个著名的实验，某人X向Y问路，Y 拼命在考虑该如何回答，甚至于当 X 被换成了另一个人 Z，Y都没能注意到。研究人员仍然在思考这个实验的全部含义，但它的确显示出在日常生活中我们只使用多么少的信息，同时也削弱了这种看法：我们了解周围所发生的事。

当我们决定进行这项研究的时候，我们的目标是加入到这个关于自我知识和意向性的持续、复杂的争论中。尽管我们感到非常熟悉决策的感觉，从“内部”去了解它却极其困难：对此进行科学研究的一个巨大障碍就是它的主观性。

每个和别人进行过争论的人都知道，人们倾向于极力证明他们所做的决定的正当性，即使旁人有充分理由相信那不过是事后的文过饰非。然而，证明这样的人错了，或者提供足够的证据让他们改变想法，可就完全是另一回事了：你凭什么说我的理由如何如何呢？

但是，有了“选择的盲点”，我们就在头脑中的意愿和行动之间撕开了一道裂缝。当我们的受试者对他们从没做过的决定给出解释的时候，我们能够确凿地向他们展示、证明他们说的不对。因此，我们的实验为观察“虚构理由”（指人们在事后虚构理由为自己的决定辩护的行为）提供了一个独特的窗口，而这是用其他方法难以得到的。我们可以把日常生活中的那些自我辩解与实验室条件下的相比较，看看描述中的细节数量，引述内容的一致性，情感的语调，甚至话语的时机与流畅程度等等，那样我们就可以创建一个理论的架构，以分析任何种类的不同点。

这个架构可以将“选择的盲点”应用于诊疗：例如，我们正在进行的两项研究调查，何以“装病”有时会发展为真病，以及“虚构理由”在强迫症中扮演了何种角色。

就重要性而言，“选择的盲点” 的效应远不止做出匆忙的判断。通过观察志愿者对偷换的选择所给出的解释（无论他们的解释是长是短，给出了量化的评分还是只给出分类，等等），我们发现这种交互会改变他们未来的偏好，甚至到了他们真的开始喜欢原本拒绝的选择项的程度。这给了我们一个难得的机会，使我们得以看到自我反馈（“我选择了这个，我宣布了我的选择，因此我必须喜欢它”）的复杂机制，我们猜测，在许多日常偏好的形成过程中，这种机制都在起作用。

我们还想探索“选择的盲点”的边界。当然，它应当不会发生在那些我们知道对我们的日常生活有重要意义的选择上。在婚礼的圣坛上，有哪个新娘或者新郎会注意不到，自己的另一半被人调包了吗？不过，在我们早期的脸孔实验结果，与这种荒唐的婚礼调包计之间，依然存在着广阔的空间。

例如，在最近的一次研究中，我们邀请了一些超市的消费者在两对果酱和茶中做出选择。为了能在被试者不注意的情况下调包，我们制作了两套魔术坛，坛子的两端各有一个盖子，内部有一个隔断。这些坛子看上去很正常，但在每一端各放了一组果酱和茶，可以很容易地切换这两组物品。

在受试者做出了选择以后，我们马上要求他们再尝一下他们所选择的结果，然后告诉我们为什么会做出这样的选择。而在他们再次品尝之前，我们切换了装有样品的容器，因此受试者拿到的正好与他们所做的选择相反。惊人的是，只有不到三分之一的人发现了其中的奥妙。即便我们切换的是味道极其不同的品种，例如肉桂苹果酱和苦味葡萄酱，意识到切换的受试者也不到一半。

我们在模拟的在线购物中也记录到了这种效应，购物对象包括诸如笔记本电脑和手机这样的消费型产品，甚至还有公寓住房。我们最近的一些实验正在探索道德和政治抉择中的影响，这一领域本来应该是深思熟虑的，但我们相信，这一领域也适合使用“选择的盲点”进行调查。

在我们的各个实验中，除了记录志愿者是否注意到了我们给他们看的不是他们当初的选择，我们还会问一些有关他们对自己的决策过程的信心的问题。如果他们在我 们这样的研究中做一个受试者，他们认为自己会感觉如何？他们认为自己会注意到结果被调包吗？80%到90%的人说他们相信自己会注意到有些事情不对劲。

想想看，当我们告诉他们我们的实验实际是怎么回事的时候，他们有多惊讶，甚至觉得无法相信。在我们的日常决策中，我们的确认为自己充分了解自己的品位，但正象那些葡萄酒鉴定家和文学批评家一样，我们常常对自己所知做了过高的估计。好消息是，这种自我过高估计不难治疗。事实上，读完这篇文章你的病就已经治好了。

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