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When McDonald's began advertising its $1 menu featuring the Big N' Tasty burger, some franchise owners were forced to sell them at a net loss; the popular item cost $1.07 to make. How could they afford to do this? Because McDonald's already knew you were going to buy fries and a Coke—products with big profit margins. It costs pennies to fill up a large drink, but you're charged more than a buck for it. This is a great deal for them and not such a great deal for us, but we can't help ourselves, because sugar lights up our brain's reward pathway.
Many recent neuroscience discoveries about food's effects on our brains and how we make decisions about food are actually gold-standard trade secrets from super chains such as McDonald's. With billions and billions served, they must be on to something.
1. Addictive properties of sugar
Nearly everything on McDonald's menu contains some sugar, from the drinks to the ketchup to the hamburger buns and fries. McDonald's knows that most people are going to shell out an extra dollar for a soft drink because sugar is addictive. Just as you can develop a physiological and psychological dependence on cocaine, you can become dependent on sugar.
Recent experiments have shown that sugar offers the hallmarks of addiction: bingeing, withdrawal and craving. Researchers kept rats from eating for 12 hours, then gave them unlimited access to food and sugar water for a brief period, and then took the food and sugar away again. They repeated this schedule for a few weeks. The rats formed a cycle of bingeing when given access to sugar, and over time they increased their intake to twice the amount from when they started. When the researchers stopped offering sugar or gave the rats an opioid blocker, which prevents the high by blocking some of the pleasurable effects in the brain, the rats showed signs of withdrawal, such as teeth-chattering and body tremors.
McDonald's recently added new menu items, including McCafe fruit smoothies, which pack in more sugar per serving than Coca-Cola. With that much sugar, McDonald's slogan is probably right: we're lovin' it.
2. The push of convenience
The fact that you can go to almost any city in the country and find a McDonald's within five minutes of driving contributes to the likelihood of compulsive eating. Similarly, recent epidemics of addiction to cocaine and heroin have accompanied increased availability and affordability of these drugs.
Part of the reason that convenience sways us so much is that we have a limited amount of impulse control. Some of us are better at resisting temptation, while some are more likely to give in. Dopamine activity in your nucleus accumbens, the brain's reward center, can disrupt your brain's decision making ability by interfering with your prefrontal cortex, the brain's impulse control region.
Dopamine has five unique types of receptors, numbered 1-5, but dopamine2 (D2) receptors seem to be most important for compulsive eating. Imaging studies show that for obese participants, fewer D2 receptors correspond to higher body-mass index. With fewer D2 receptors, they're more likely to eat compulsively; it becomes even harder to resist super-sizing their meal.
3. The brain's economy and the Value Meal
Low prices minimize the pain associated with parting with your hard-earned money. Decisions become difficult when two opposing forces try to sway you, in this case, spending money versus eating. The brain weights the costs and benefits of a decision in a region called the orbitofrontal cortex. Brain-imaging has shown that losing money can cause your brain to experience the same pattern of activity as when you stub your toe. Losing money hurts. Yet McDonald's manages to sidestep this problem by pricing a sandwich cheaper than the Sunday newspaper (which helps make up for the pain of your $40 filet mignon the night before). At McDonald's, you get the rewarding meal without the pain of losing money. They make the decision easy for your brain.
4. Our brains prefer high-calorie foods
As suggested by Jonah Lehrer in "The Frontal Cortex," our brains evolved during a time when food was scarce, so we became adept at choosing foods that packed calories.
In one recent experiment, scientists used genetically engineered mice that were missing sugar receptors and therefore unable to detect sweetness in food. The researchers then gave the mice free access to two water dispensers, one with sugar water and one with regular water. Initially, the mice showed no preference; sugar water tasted just like regular water. However, after several hours, the mice shifted to drinking almost exclusively from the sugar water dispenser. To ensure that the mice preferred the calories, but could not detect the taste, the researchers offered them water sweetened with sucralose (e.g. Splenda). The mice didn't take it.
When the scientists analyzed the mice brains, they found that the mice released dopamine in response to sugar water, even though they couldn't taste it, but not in response to regular water or sucralose. Our brains can tell the difference between high calorie foods and diet foods even if they taste the same.
5. Addictive properties of speed
Drugs have a hierarchy of addictive potential based on the speed that they reach your brain. Pills have to be swallowed, broken down in the stomach, pushed into the digestive tract and then absorbed into the blood stream before they can reach your brain. The reward you experience comes relatively long after you take the drug. Heroin skips the lag time; injecting it directly into your bloodstream sends it to your brain within seconds. The closer you can pair a stimulus with a reward, the stronger the association will be.
Similarly, fast food provides a quick fix for hunger. You don't even have to get out of your car to pick up a Big Mac. You place your order at the drive-thru and within two minutes you can take the first bite as you drive home. You can hardly get a pan hot enough to fry in that time. The sooner you have the burger in hand, the sooner it can trigger the release of the cocktail of rewarding chemicals in your brain.
6. Brains like branding
Just as Pavlov was able to get a dog to salivate at the sound of a bell, McDonald's gets your juices flowing anytime you hear their jingle. Pavlov showed that if he rang a bell before giving food to a dog, eventually the bell itself would whet its appetite.
Across the nation, McDonald's provides a consistent experience every time you enter its doors. The employees recite a scripted greeting, the menu looks the same, and the same images and logos are posted on the walls. The more consistent the experience, the more strongly your brain associates the Golden Arches with the meal that follows.
The brain's reward chemical is dopamine, a molecule that's released when you experience something you enjoy. However, one of the brilliant aspects of the brain is its ability to learn and make predictions about the world based on past experiences. When the brain learns that a certain cue is associated with a reward, dopamine neurons learn to fire whenever the cue appears, even before the reward is given. Dopamine does more than simply reward you; it also motivates you to seek the pleasure again. As soon as you see the cue, your brain begins to anticipate the reward. The anticipation is part of the pleasure. Would you like fries with that?
7. McNuggets stoke your memory
In a recent study, researchers gave children chicken nuggets in an unmarked container or in McNuggets packaging. Not surprisingly, kids preferred the ones that resembled a Happy Meal. Neuroscience research has shown that a big part of the pleasure of eating stems from memories tied to the food, not taste alone.
In a brain-imaging study of the Pepsi Challenge, Read Montague at Baylor College of Medicine first gave participants a blind taste test of Coca-Cola and Pepsi while in an MRI scanner. The subjects preferred Coca-Cola and Pepsi equally, and both of the sodas caused brain activity in the ventromedial prefrontal cortex, a region involved in pleasure and reward. However, when the subjects were told they were drinking Coke, they shifted their preference. Now, 75 percent preferred Coke. What's more, their brain activity changed. The hippocampus, the brain region crucial to memory formation, lit up with activity, suggesting that drinking Coca-Cola, rather than a generic soft-drink, stirs up your memories of Coca-Cola.
Similarly, eating a McNugget not only sates your appetite for chicken (and the glue that holds the McNugget together), it also reminds you of your childhood, the cool Transformers toy you got in your Happy Meal, and the first time you were big enough to order the 10-piece instead of the 4-piece.
参考译文：
麦当劳开始了新的1美元食物宣传攻势，又大又美味的汉堡包引人驻足。这种大受欢迎的食物，平均制作成本就要1.07美元，一些加盟店主只能亏本出售。麦当劳会不会亏损呢？当然不会。因为麦当劳知道：人们买汉堡包的时候也会买上一杯可乐。这才是麦当劳的巨额利润来源——一大杯可乐成本只需几美分，麦当劳卖给你的价格却不止1美元。麦当劳的如意算盘绝不可能让我们占到便宜，问题是我们还是忍不住要光顾他们。这是为什么呢？答案就是麦当劳的读心术——麦当劳知道你的脑子里想什么。
神经科学领域的很多新发现揭示了食物如何影响大脑、人如何选择食物的奥秘。这些科学发现恰恰就是麦当劳等超级快餐连锁如何盈利的商业机密。让我们看看快餐业食物和服务背后的真相。
1 糖会成瘾
麦当劳提供的几乎所有食物都含糖——番茄酱、饮料、汉堡、薯条等等。麦当劳非常清楚，大多数人在麦当劳就餐时都会购买饮料，而喝含糖的饮料也会成瘾。就像对可卡因产生心理依赖和躯体依赖，人也可以对糖产生依赖性。
最新研究发现小鼠对糖有各种成瘾的表现：过度食用、戒断和渴求。研究人员给小鼠禁食12小时后，在短时间内提供不限量的食物和糖水，然后撤走。研究人员重复这个周期几周以后，小鼠在有糖水供应时会大饮特饮，每次的饮用量渐渐增加到开始时饮用量的两倍。研究人员停止为小鼠提供糖水或给予阿片受体阻断药后，小鼠出现戒断症状，如牙齿打颤、全身震颤。
麦当劳最近又推出一系列新的食物，其中麦咖啡水果沙冰的含糖量甚至超过可口可乐。原因可能真如麦当劳的宣传语：我就喜欢！（I'm Lovin' it.）
2 便利让人冲动
在美国所有城市，都能在5分钟车程范围内找到麦当劳餐厅。这很容易引起强迫性暴食。与之相似的情景是，最近可卡因、海洛因的出货量增加、获取方便，瘾君子的数量随之猛增。
便利让人们动心的原因就是：人控制冲动的次数是有数量限制的。有人对诱惑有超强的抵抗力，也有人很容易就屈服，这种区别的根源应该归因于大脑构造的区别。人脑中有个叫做伏隔核的部位，富含神经递质多巴胺。伏隔核的功能是产生奖赏效应——这个脑区激动会带给机体美好的感受和体验。而伏隔核中多巴胺的作用也影响到负责控制冲动的前额叶皮层，人面对诱惑时的决断力也因此被削弱了。
多巴胺受体有5种不同的类型。不过多巴胺2型受体（D2受体）似乎和强迫性暴食行为的关系最为密切。肥胖志愿者脑部成像的结果显示：脑内D2受体越少，体重指数越高。脑内D2受体较少的人，也更容易出现强迫性暴食。
3 超值套餐和大脑经济学
拱手送出辛苦挣来的钱固然让人心痛，低价的诱惑又减轻了这种痛苦。这种情况下，金钱和美食委实难以选择。人脑的前额皮质负责衡量付出和收益，大脑成像显示：失去钱财时脑部活动的模式和被撞到脚趾时是一样的。不过，麦当劳尽量避免受到人们这种心理活动的影响——他们把三明治的价格定得比一份周末报纸还便宜，甚至你前一天晚上为菲力牛排付出40美元造成的痛苦也会因此减轻。人们在麦当劳获得的都是奖赏餐，毫无失去钱财的痛苦，这时大脑做出的决定一定是麦当劳喜欢的。
4 大脑喜欢高热量食物
进化过程使大脑倾向于做出这样的抉择：食物匮乏的时候，我们优先选择高热量的食物。
最近科学家使用基因改造的小鼠进行了一项研究，这些小鼠对糖的味觉缺失，无法感受到食物中的甜味。小鼠可以自由使用两个饮水机，一个饮水机中是糖水，另一个则装着清水。最初，小鼠没有表现出对哪种饮品的偏好，因为糖水对它们来说在口味上和清水毫无区别。不过，几个小时之后，小鼠就几乎只喝糖水了。为了验证小鼠选择糖水是因为糖水热量高，而不是因为尝到了甜味，研究人员又为小鼠准备了有甜味但低热量的三氯蔗糖水。小鼠的选择仍然是高热量的糖水。
分析小鼠的大脑后发现，即使小鼠尝不出糖水的甜味，糖水仍然能促进脑内释放多巴胺；清水和三氯蔗糖水就没这个效果。就算你的舌头无法辨别高热量食品和减肥食品有什么不同，你的大脑也有自己的判断。
5 快捷也会成瘾
毒品的成瘾性和进入大脑的速度密切相关。食用的毒品需要先被吞下，在胃里分解，进入小肠，吸收进入血液，然后才能进入大脑，产生奖赏效应。海洛因就不需要费这么多周折，血管内注射几秒钟后就进入大脑。海洛因很容易让人成瘾的一个原因就是：刺激和奖赏越容易被联系到一起，两者之间的关系就越紧密。
同样，快餐也能快捷地填饱你的肚子，激发大脑产生奖赏体验。你甚至不需要停车就能拿到一个大汉堡；开车回家的路上经过穿梭餐厅2分钟，你就可以大快朵颐。如果你自己下厨，这么点时间锅还没热呢。麦当劳越快捷地把汉堡包交到你手上，你大脑里诱发奖赏体验、让你感觉愉快的化学物就释放得越快。
6 大脑喜欢品牌攻势
巴普洛夫在每次喂狗前摇铃，一段时间之后，只摇铃就能让狗垂涎三尺，这就是著名的条件反射试验。麦当劳当然也深谙此道。
所有的麦当劳给顾客的体验都一样——走进大门听到千篇一律的员工问候，看到的菜单如出一辙，墙上的图案和标志也是一模一样。每次去麦当劳的体验越是一致，大脑中食物和麦当劳之间的联系就越强烈。
经历愉快的体验时，脑内会释放和奖赏有关的化学物质——多巴胺。不过大脑的另一神奇之处是它能够学习，并根据过去的经验进行预测。如果大脑通过学习，在某些体验和某种线索之间产生了关联，只要这种线索出现，含有多巴胺的神经元就会兴奋，不管令人愉快的体验有没有出现。此外，多巴胺不仅仅能激发奖赏体验，还能促使人们再次寻求快感，期待也成了快感的一部分。你想吃薯条么？
7 麦乐鸡勾起美好回忆
最近的一项研究中，研究人员给儿童准备了一些炸鸡块，其中一些是麦乐鸡包装的，另外一些则是没有标识的。毫无意外，孩子们更喜欢前者——它们很像开心乐园餐中的鸡块。神经科学研究显示，进食带来的愉悦体验不止来自唇舌的快感，还有很大一部分来自和食物有关的美好回忆。
2003年，百事可乐公司的“百事挑战”系列营销活动中有一个著名的试验，研究人员请受试者品尝两种可乐，但不告诉他们哪种是可口可乐，哪种是百事可乐，同时利用功能性磁共振对受试者的大脑进行扫描。品尝后，表示喜欢两种可乐的人各占一半。功能性脑扫描结果显示：两种可乐都诱发大脑腹内侧前额叶皮质的活动，这个活动和愉悦感和奖赏过程有关。在被告知喝的是哪种可乐的时候，受试者的喜好似乎发生了变化，认为可口可乐更好喝的人数比例增加到了75%。更重要的是，他们的大脑活动发生了明显变化。除了前额叶皮质，和记忆密切相关的海马区也同时兴奋。这说明，可口可乐不同于普通的软饮料，它能引起人的美好回忆。
同样，麦乐鸡不仅满足了你对鸡块的食欲，是不是也让你想起欢乐的童年时光，开心乐园套餐里超酷的变形金刚，还有长大后第一次买大盒麦乐鸡的情景呢？
原文链接：7 Things McDonald’s Knows About Your Brain
