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当我们品尝食物时,大脑在想些什么?

发布者: 千缘 | 发布时间: 2020-9-8 01:55| 查看数: 146| 评论数: 0|

为什么我们能够感受某些食物好吃,某些食物不好吃?Camilla Arndal Andersen是一位神经科学家,她的专长是食品科学。Camilla通过脑部扫描来研究人们的味觉。她揭示了我们大脑潜意识中体验食物的方式,并展示了这些数据如何帮助我们在不牺牲味道的情况下吃得更健康。



So I had this very interesting experience five years ago. You know, me and my husband, we were out grocery shopping, as we do every other day, but this time, we found this fancy, you know, I'm talking fair-trade, I'm talking organic, I'm talking Kenyan, single-origin coffee that we splurged and got. 五年前,我碰到了一件有趣的事儿。有一天,和往常一样,我和我丈夫去买菜,但这次我们看到了一家特别高大上的店,有这么一类公平贸易、有机,来自肯尼亚单一产区的咖啡,我们买了好多。

And that was when the problem started already. You know, my husband, he deemed this coffee blend superior to our regular and much cheaper coffee, which made me imagine a life based solely on fancy coffee and I saw our household budget explode. 这时候问题就来了。我丈夫觉得买的这类咖啡比平常普通便宜的咖啡要好喝,我不禁想象了一下只有高档格咖啡的生活,以我们的经济状况肯定吃不消。

And worse ... I also feared that this investment would be in vain. That we wouldn't be able to notice this difference after all. Unfortunately, especially for my husband, he had momentarily forgotten that he's married to a neuroscientist with a specialty in food science. 更重要的是,我更担心这类投资没什么意义。毕竟我们根本喝不出来区别。不巧的是,我丈夫时常忘记他的妻子是一位神经科学家,专长是食品科学。

Alright? So without further ado, I mean, I just put him to the test. I set up an experiment where I first blindfolded my husband. 就是这么个情况。那么事不宜迟,我赶忙丢给他一个测试。我设置了一个实验,也就是把我丈夫的眼睛蒙上。

Then I brewed the two types of coffee and I told him that I would serve them to him one at a time. Now, with clear certainty, my husband, he described the first cup of coffee as more raw and bitter. You know, a coffee that would be ideal for the mornings with the sole purpose of terrorizing the body awake by its alarming taste. 然后冲泡了两种咖啡,并告诉他我一次给他喝一种。我的丈夫在描述第一杯咖啡的时候十分肯定地说,这杯更苦更涩。就是那种一大早起床能让人立马清醒的味道。

The second cup of coffee, on the other hand, was both fruity and delightful. You know, coffee that one can enjoy in the evening and relax. Little did my husband know, however, that I hadn't actually given him the two types of coffee. I had given him the exact same cup of coffee twice. 而第二杯咖啡,他说更令人愉悦,还带些果味,是适合晚上喝的那种咖啡。但我的丈夫并不知道我其实根本没有给他喝两种咖啡,而是同一杯咖啡给他喝了两次。

And obviously, it wasn't this one cup of coffee that had suddenly gone from horrible to fantastic. No, this taste difference was a product of my husband's own mind. Of his bias in favor of the fancy coffee that made him experience taste differences that just weren't there. Alright, so, having saved our household budget, and finishing on a very good laugh, me especially -- 显然,并不是这一杯咖啡突然变得好喝,而是我丈夫的心理作用。因为他对来自肯尼亚单一产区的有机咖啡的偏好让他体会到了本不存在的味觉差异。所以呢,我轻而易举地省下了家庭开支,还逗得大家笑了笑。我呢——

I then started wondering just how we could have received two such different responses from a single cup of coffee. Why would my husband make such a bold statement at the risk of being publicly mocked for the rest of his life? 开始思索我们是如何接收两种不同信息的。为什么我的丈夫可以充满信心的作答而不怕被人在公共场合嘲笑呢?

The striking answer is that I think you would have done the same. And that's the biggest challenge in my field of science, assessing what's reality behind these answers that we receive. Because how are we going to make food tastier if we cannot rely on what people actually say they like? 别笑,其实大家都一样。而这也是我这门学科最大的挑战,即这些答案背后的真相是什么。因为如果我们都不能相信人们说的话,又该怎么才能让食物变好吃呢?

To understand, let's first have a look at how we actually sense food. When I drink a cup of coffee, I detect this cup of coffee by receptors on my body, information which is then turned into activated neurons in my brain. Wavelengths of light are converted to colors. Molecules in the liquid are detected by receptors in my mouth, and categorized as one of five basic tastes. That's salty, sour, bitter, sweet and umami. Molecules in the air are detected by receptors in my nose and converted to odors. And ditto for touch, for temperature, for sound and more. All this information is detected by my receptors and converted into signals between neurons in my brain. Information which is then woven together and integrated, so that my brain recognizes that yes, I just had a cup of coffee, and yes, I liked it. And only then, after all this neuron heavy lifting, do we consciously experience this cup of coffee. And this is now where we have a very common misconception. 要想一探究竟,我们还得来看看人类是如何感知食物的。当我喝咖啡的时候,身体中的受体分子会感知到,接着信息便会传到活跃的大脑神经元。光波被转化为颜色。嘴巴里的受体感知到液体分子然后把它们归类为五种基本味道,即酸、甜、苦、咸、鲜。鼻子里的受体会感知空气分子并转化为香味。这些也适用于触摸,温度,声音等等。这一切信息都会被身体里的接受体检测到,并转化为大脑神经元之间的信号,然后信息被编码并组合,这样大脑就可以识别出刚刚喝了杯咖啡,还蛮喜欢的。只有在所有神经元都干完活后我们才能有意识地去体会这杯咖啡。

People tend to think that what we experience consciously must then be an absolute true reflection of reality. But as you just heard, there are many stages of neural interpretation in between the physical item and the conscious experience of it. Which means that sometimes, this conscious experience is not really reflecting that reality at all. Like what happened to my husband. That's because some physical stimuli may just be so weak that they just can't break that barrier to enter our conscious mind, while the information that does may get twisted on its way there by our hidden biases. And people, they have a lot of biases. 这时人们常常有些误解。人们总觉得我们有意识感知到的东西一定反映出了绝对的现实。但正如我刚刚所说的,神经解释在实物和有意识的经验之间有很多步骤,也就是说,有的时候,有意识的体验并不一定能反应出真实情况。正如我的丈夫一样。这是因为一些物理刺激可能太过微弱,并不能打破重重关卡最后进入我们的意识之中,而这个信息则会被隐藏的偏见所扭曲。人类有太多偏见。

Yes, if you're sitting there right now, thinking ... you could probably have done better than my husband, you could probably have assessed those coffees correctly, then you're actually suffering from a bias. A bias called the bias blind spot. Our tendency to see ourselves as less biased than other people. 没错,如果你在想,你肯定不会和我丈夫一样,并能辨别出这只是同一杯咖啡,那你可能的确有一种偏见,即偏见盲点。我们经常认为自己没有别人那么多的偏见。

And yeah, we can even be biased about the biases that we're biased about. 没错,我们甚至可能因为我们有偏见的偏见而有偏见。

Not trying to make this any easier. 再往前一步说,

A bias that we know in the food industry is the courtesy bias. This is a bias where we give an opinion which is considered socially acceptable, but it's certainly not our own opinion, right? And I'm challenged by this as a food researcher, because when people say they like my new sugar-reduced milkshake, do they now? 食品业中常见的,是礼貌性偏见。这种偏见是,我们给出一个社会上普遍认可的观点,但这绝对不是我们自己的观点。作为一名食品科学家,我对此不以为然,当人们说他们喜欢我手里的低糖奶昔的时候,是真心的吗?

Or are they saying they like it because they know I'm listening and they want to please me? Or maybe they just to seem fit and healthy in my ears. I wouldn't know. But worse, they wouldn't even know themselves. Even trained food assessors, and that's people who have been explicitly taught to disentangle the sense of smell and the sense of taste, may still be biased to evaluate products sweeter if they contain vanilla. Why? Well, it's certainly not because vanilla actually tastes sweet. It's because even these professionals are human, and have eaten lot of desserts, like us, and have therefore learned to associate sweetness and vanilla. 还是说,他们只是知道我在听这些话,而他们只想逗我开心?又或者他们只想让我觉得他们挺健康的,谁知道呢。更有趣的是,他们可能并没有意识到自己的行为。甚至经过严格训练的食品评估者,那些经过特殊训练学习如何分别味觉和嗅觉的人,都会因为食物里有香草更认为这份食物比较甜。为什么?当然这不是因为香草真的比较甜。而是因为这些专家都是人,和我们一样吃了很多甜点并因此将甜度和香草联系在了一起。

So taste and smell and other sensory information is inextricably entangled in our conscious mind. So on one hand, we can actually use this. We can use these conscious experiences, use this data, exploit it by adding vanilla instead of sugar to sweeten our products. But on the other hand, with these conscious evaluations, I still wouldn't know whether people actually liked that sugar-reduced milkshake. 所以味觉嗅觉和其他感官在我们的意识中是难以分割的。所以一方面讲,我们可以利用这些有意识的体验,这些数据,来研究加多少香草来代替糖去增加食品的甜度。但另一方面,有了这些有意识的评估,我还是不知道到底人们是不是真的喜欢低糖奶昔。

So how do we get around this problem? How do we actually assess what's reality behind these conscious food evaluations? The key is to remove the barrier of the conscious mind and instead target the information in the brain directly. And it turns out our brain holds a lot of fascinating secrets. Our brain constantly receives sensory information from our entire body, most of which we don't even become aware of, like the taste information that I constantly receive from my gastrointestinal tract. And my brain will also act on all this sensory information. It will alter my behavior without my knowledge, and it can increase the diameter of my pupils if I experience something I really like. And increase my sweat production ever so slightly if that emotion was intense. And with brain scans, we can now assess this information in the brain. 那我们该如何解决这个问题呢?如何区分有意识的食品评估背后的真相呢?关键在于要移除意识的重重阻拦,直接尝试去获取大脑中的信息。事实证明,我们的大脑藏有许多不为人知的秘密。大脑通常接收来自全身的感知信息。多半我们都没有意识到,比如胃肠道的味道信息。大脑会自动处理这些味道信息,会在人们没有意识到的情况下改变行为,并扩大瞳孔,仿佛我们真的经历了喜欢的事情一样。这个反应还会在情绪激动的时候提高汗液产出。大脑扫描为我们提供了大脑中的这些信息。

Specifically, I have used a brain-scanning technique called electroencephalography, or "EEG" in short, which involves wearing a cap studded with electrodes, 128 in my case. Each electrode then measures the electrical activity of the brain with precision down to the millisecond. The problem is, however, it's not just the brain that's electrically active, it's also the rest of the body as well as the environment that contains a lot of electrical activity all the time. To do my research, I therefore need to minimize all this noise. So I ask my participants to do a number of things here. First off, I ask them to rest their head in a chin rest, to avoid too much muscle movement. I also ask them to, meanwhile, stare at the center of a computer monitor to avoid too much eye movements and eye blinks. And I can't even have swallowing, so I ask my participants to stick the tongue out of their mouth over a glass bowl, and then I constantly let taste stimuli onto the tongue, which then drip off into this bowl. 我所用的一种大脑扫描技术叫脑电图,即EEG,这个过程要求人们带上一顶带有128个电极的帽子。每个电极都会测量大脑的电活动,精确到毫秒。然而问题是,并不只有大脑才有电活动,人的全身,包括周遭环境都包含许多电活动。为了完成研究,我得尽力去除这些外界因素影响。所以我让实验者做了如下一些事。第一,我让他们把头放到腮托上,尽量避免肌肉活动。我还让他们盯着电脑中央,以避免过多的眼球转动及眨眼。甚至还不能咽口水,所以我让他们把舌头伸出来放到玻璃碗上,并不停放上味觉刺激物,然后他们的口水就可以滴到碗里。

And then, just to complete this wonderful picture, I also provide my participants with a bib, available in either pink or blue, as they please. 之后,为了画龙点睛,我还给了他们一个围兜,蓝色或粉色,随他们挑。

Looks like a normal eating experience, right? 看起来就像是个正常进食活动,对吧?

No, obviously not. And worse, I can't even control what my participants are thinking about, so I need to repeat this taste procedure multiple times. Maybe the first time, they're thinking about the free lunch that I provide for participating, or maybe the second time, they're thinking about Christmas coming up and what to get for Mom this year, you know. But common for each response is the response to the taste. So I repeat this taste procedure multiple times. Sixty, in fact. And then I average the responses, because responses unrelated to taste will average out. 才怪。而且,因为我无法控制他们的想法,所以得不停重复这个实验很多次。或许第一次,他们在想我提供的免费午餐,第二次,在想即将到来的圣诞得给妈妈买什么。但每次都是对味道的反应所以我不停重复这些步骤。重复了六十次。然后对实验结果去了平均值,因为那些无关味觉的都可以被平均掉。

And using this method, we and other labs, have investigated how long a time it takes from "food lands on our tongue" until our brain has figured out which taste it's experiencing. Turns out this occurs within the first already 100 milliseconds, that's about half a second before we even become aware of it. And next up, we also investigated the taste difference between sugar and artificial sweeteners that in our setup taste extremely similar. In fact, they tasted so similar that half my participants could only barely tell the taste apart, while the other half simply couldn't. But amazingly, if we looked across the entire group of participants, we saw that their brains definitely could tell the taste apart. 用了这个办法,我和其他实验室研究了从“食物碰到舌头”,到大脑终于弄明白那是什么样的味道需要多久。我们发现,整个过程发生在前100毫秒,也就是我们有所感知之前半秒钟。之后,我们还研究了糖和其他人工甜味剂的味觉差异,发现并无不同。甚至可以说,半数的受试者都很难区分,而另一半则完全无法区分。最令人惊叹的是,如果我们将整组受试者进行比较,他们的大脑绝对可以识别差异。

So with EEG and other brain-scanning devices and other physiological measures -- sweat and pupil size -- we have new gateways to our brain. Gateways that will help us remove the barrier of the conscious mind to see through the biases of people and possibly even capture subconscious taste differences. And that's because we can now measure people's very first response to food before they've become conscious of it, and before they've started rationalizing why they like it or not. We can measure people's facial expressions, we can measure where they're looking, we can measure their sweat response, we can measure their brain response. And with all these measures, we are going to be able to create tastier foods, because we can measure whether people actually like that sugar-reduced milkshake. And we can create healthier foods without compromising taste, because we can measure the response to different sweeteners and find the sweetener that gives the response that's more similar to the response from sugar. 所以有了脑电图和其他大脑扫描设备及其他生理测试的辅助——研究汗液和瞳孔——我们走上了通往大脑的新道路。这条路可以帮助我们免去意识的屏障,看穿人类的偏见,甚至还能捕捉潜意识中的味道差异。这是因为现在我们可以测量人体对食物的第一反应,甚至先于人类的自我认知,在他们开始思索到底喜不喜欢之前。我们可以研究人的面部表情,他们在看哪,可以研究汗液反应,大脑反应。所有的这些测试都能帮助我们创造更好吃的食物,因为我们能知道人们究竟喜不喜欢那杯低糖奶昔。我们还能在不影响味道的前提下产出更健康的食品,因为我们可以研究人们对不同甜味剂的反应,并找出哪一种最接近糖。

And furthermore, we can just help create healthier foods, because we can help understand how we actually sense food in the first place. Which we know surprisingly little about. For example, we know that there are those five basic tastes, but we strongly suspect that there are more, and in fact, using our EEG setup, we found evidence that fat, besides being sensed by its texture and smell, is also tasted. Meaning that fat could be this new sixth basic taste. And if we figure out how our brain recognizes fat and sugar, and I'm just dreaming here, but could we then one day create a milkshake with zero calories that tastes just like the real deal? Or maybe we figure out that we can't, because we subconsciously detect calories via our receptors in our gastrointestinal tract. The future will show. 进一步讲,我们可以生产出更健康的食物,因为我们能帮助人们理解人类是如何感知食物的。这点我们知之甚少。比如,我们知道最基本的五种味道,但并不知道还有更多的味道,事实上,利用脑电图,我们发现脂肪,除了它的气味和质地,也是有味道的。也就是说我们有了第六种基本味道,并且如果我们能知道大脑是如何识别脂肪和糖分的话,做个比方,那是不是意味着有朝一日,我们能制造出零卡路里的“原味”奶昔?或许我们能知道我们做不到,因为潜意识中检测卡路里的感知器是胃肠道。未来我们会得到更加清晰的结论。

Our conscious experience of food is just the tip of the iceberg of our total sensation of food. And by studying this total sensation, conscious and subconscious alike, I truly believe that we can make tastier and healthier foods for all. 我们对食物的有意识经历只是我们对食物感知的冰山一角。通过研究全面感知,不管有意识还是潜意识的,我认为我们都可以为人类创造美味又健康的食物。

Thank you. 谢谢。



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