Science of Smiling

A smile is one of the most powerful things a human face can do. In a fraction of a second it can show warmth, ease tension and help strangers trust each other. We usually think of it as simple: we feel happy, so we smile. But research suggests that the link also works, at least a little, in the other direction.

微笑是人脸所能做出的最有力量的动作之一。在不到一秒的时间里，它就能传递温暖、缓和紧张，让陌生人彼此信任。我们通常觉得这很简单：心里高兴，所以微笑。但研究表明，这种联系至少在一定程度上也能反过来起作用。

Smiling is one of the few human behaviors found everywhere. In studies of very different cultures, from American students to villagers in Papua New Guinea, people recognized a happy smile more easily than any other facial expression. This suggests that the smile is part of our biology. To understand how and why we smile, scientists study the brain, social behavior and even our closest animal relatives.

微笑是少数几种在世界各地都能见到的人类行为之一。在针对差异极大的各种文化所做的研究中，从美国大学生到巴布亚新几内亚的村民，人们认出开心的笑容都比认出其他任何面部表情更容易。这说明微笑是我们生物本能的一部分。为了弄清我们如何微笑、为什么微笑，科学家研究大脑、社会行为，甚至研究我们在动物界中最近的亲戚。

Not all smiles are the same. In the 1860s the French doctor Guillaume Duchenne studied the human face by stimulating its muscles with small electric currents. He noticed that a smile of real joy uses not only the muscles around the mouth but also a ring of muscle around the eyes, the orbicularis oculi. It lifts the cheeks and creates the small wrinkles at the corners of the eyes known as crow's feet. Today this is called a 'Duchenne smile'.

并不是所有的微笑都一样。19世纪60年代，法国医生纪尧姆·杜兴用微弱的电流刺激面部肌肉，以此研究人的面孔。他注意到，真正因快乐而产生的微笑不仅会用到嘴部周围的肌肉，还会用到环绕眼睛的一圈肌肉，即眼轮匝肌。这块肌肉会把脸颊往上提，并在眼角形成细小的皱纹，也就是人们常说的鱼尾纹。如今，这种微笑被称为“杜兴式微笑”。

A polite or social smile usually involves only the mouth, and we can produce it whenever we want. People are fairly good at telling the two kinds apart, often without knowing how they do it. They are not perfect, though. Later studies showed that many people can also crinkle their eyes on purpose, so a smile that looks real is not always a sign of real happiness.

礼貌性的或社交性的微笑通常只动用嘴部，而且我们想笑就能笑出来。人们相当善于分辨这两种微笑，而且往往说不清自己是怎么分辨出来的。不过，人们也并非从不出错。后来的研究发现，很多人也能有意地眯起眼睛，所以一个看起来很真诚的微笑，并不一定代表真正的快乐。

Popular articles often say that every smile floods the brain with dopamine, serotonin and endorphins. The real picture is less dramatic. Pleasant experiences do activate the brain's reward system, and dopamine is part of that system. But there is little direct evidence that the movement of a smile by itself releases a measurable burst of these chemicals.

科普文章常说，每次微笑都会让大脑充满多巴胺、血清素和内啡肽。真实情况没有这么夸张。愉快的经历确实会激活大脑的奖赏系统，而多巴胺正是这个系统的一部分。但几乎没有直接证据表明，仅仅做出微笑的动作就能释放出可测量的大量这些物质。

The idea that a forced smile can lift your mood comes largely from a famous 1988 study by the German psychologist Fritz Strack and his colleagues. People who held a pen between their teeth, which pushes the face into a kind of smile, rated cartoons as slightly funnier than people who held the pen with their lips. In 2016, seventeen labs repeated the experiment and found no effect. A larger international project in 2022 found that posing a smile can make people feel a little happier, but the effect was small.

“强颜欢笑也能改善心情”这一观点，很大程度上来自德国心理学家弗里茨·施特拉克及其同事在1988年做的一项著名研究。用牙齿咬住一支笔的人，脸部会被迫做出类似微笑的表情，他们觉得漫画比用嘴唇含住笔的人稍微好笑一些。2016年，十七个实验室重复了这个实验，却没有发现任何效果。2022年，一个规模更大的国际项目发现，摆出微笑的表情确实能让人稍微开心一点，但效果很小。

It is hard to look at a smiling face without smiling back. Some scientists link this to mirror neurons, brain cells that become active both when we do something and when we watch someone else do it. A team in Parma, Italy, first found them in monkeys in the 1990s. Whether they really explain why smiles spread from person to person is still debated.

看着一张笑脸却不回以微笑，是很难做到的。一些科学家把这种现象与镜像神经元联系起来。镜像神经元是一种脑细胞，我们自己做某个动作时它会被激活，看到别人做同样的动作时它也会被激活。20世纪90年代，意大利帕尔马的一个研究团队首先在猴子身上发现了它们。但它们是否真的能解释微笑为何会在人与人之间传递，目前仍有争议。

Copying another person's expression without thinking about it is called facial mimicry. In experiments by the Swedish psychologist Ulf Dimberg, people's smiling muscles reacted to pictures of happy faces within a fraction of a second, even when they had been told not to react. This automatic copying may have helped our ancestors show that they were friendly and keep their groups together.

不自觉地模仿别人的面部表情，叫作面部模仿。在瑞典心理学家乌尔夫·丁伯格的实验中，即使事先要求参与者不要做出反应，他们的微笑肌肉仍会在不到一秒内对开心面孔的照片作出反应。这种自动的模仿也许曾帮助我们的祖先表明自己的友好，并让群体保持团结。

Many researchers believe the human smile has its roots in other primates. Monkeys and apes often show a 'silent bared-teeth display': they pull back their lips and show their teeth without making a sound. In many species this signals fear or submission. In chimpanzees and bonobos, however, it can also mean something like 'I'm friendly', which is much closer to what we call a smile.

许多研究者认为，人类的微笑起源于其他灵长类动物。猴子和猿类常常会做出一种“无声露齿”的表情：它们把嘴唇向后拉，露出牙齿，却不发出任何声音。在许多物种中，这表示恐惧或顺从。但在黑猩猩和倭黑猩猩身上，它也可以表示类似“我很友好”的意思，这已经和我们所说的微笑相当接近了。

The human smile may have grown out of this same message: I am not a threat. As human groups became larger, the ability to show peaceful intentions quickly became more and more useful. The result is a small movement of a few muscles that people understand across almost any language barrier.

人类的微笑也许正是从同样的信息演变而来的：我没有威胁。随着人类群体越来越大，能够迅速表明和平意图变得越来越有用。最终形成的，是几块肌肉的一个小小动作，人们几乎可以跨越任何语言障碍读懂它。

The smile itself is universal, but the rules about when to smile are not. In the United States it is normal and friendly to smile at strangers. In Russia people usually save their smiles for those they know, and a stranger who smiles for no clear reason may seem insincere. A well-known Russian proverb says that laughing for no reason is a sign of a fool. It is about laughter, not smiling, but people often quote it to explain this attitude.

微笑本身是全人类共通的，但关于什么时候该微笑的规矩却各不相同。在美国，对陌生人微笑是正常而友好的。在俄罗斯，人们通常只对认识的人微笑，一个无缘无故微笑的陌生人可能会显得不真诚。俄罗斯有一句很有名的谚语，说无缘无故地笑是傻瓜的标志。这句话讲的是笑，而不是微笑，但人们常常引用它来解释这种态度。

In Japan and other East Asian cultures, a smile can also hide embarrassment or discomfort. Finns and other Nordic people are often described as saving their smiles for real feelings, though this is a general impression, not a rule. A 2016 study of 44 cultures found that in some countries, people judged smiling faces in photos as less intelligent than neutral ones. A smile that seems warm in one place can look fake or even foolish in another.

在日本和其他东亚文化中，微笑也可能用来掩饰尴尬或不自在。人们常说芬兰人和其他北欧人只在有真实感受时才微笑，但这只是一种笼统的印象，并不是规律。2016年一项涵盖44种文化的研究发现，在一些国家，人们认为照片上微笑的面孔不如表情平静的面孔聪明。一个在某地显得温暖的微笑，换个地方可能就显得虚假，甚至有点傻。

Scientists have long studied how smiling and laughter are connected to health. People who smile more tend to report greater life satisfaction and fewer signs of depression, although this may simply be because happy people smile more. A few experiments suggest that smiling can help the body recover from stress. In a 2012 study at the University of Kansas, people who held chopsticks in their mouths in a smiling position had a lower heart rate after a stressful task. Other small studies suggest that smiling may make pain feel slightly weaker.

科学家很早就开始研究微笑、大笑与健康之间的关系。经常微笑的人通常表示自己对生活更满意，抑郁的迹象也更少，不过这也可能只是因为快乐的人本来就更爱笑。一些实验表明，微笑也许能帮助身体从压力中恢复。在堪萨斯大学2012年的一项研究中，用嘴咬住筷子、使脸呈微笑状的人，在完成一项有压力的任务后心率更低。另一些小规模研究则表明，微笑可能会让疼痛感稍微减轻。

A 2010 study looked at photos of baseball players from 1952 and found that players with broad, genuine smiles had lived about seven years longer than players who did not smile. The study became famous. But in 2018 another team repeated it with a much larger group of players and found no link between smiling in a photo and living longer.

2010年的一项研究分析了1952年棒球运动员的照片，结论是：笑得灿烂、真诚的球员比不笑的球员平均多活了大约七年。这项研究因此出了名。但在2018年，另一个团队用规模大得多的球员样本重做了这项研究，却没有发现照片上的微笑与寿命长短之间有任何关联。

Research in social psychology shows that smiling changes how other people see us. In many studies, smiling people are rated as friendlier, more attractive and more trustworthy than people with a neutral face. The effect is not the same everywhere, though: as the study of 44 cultures showed, a smile does not always make someone look smarter.

社会心理学研究表明，微笑会改变别人对我们的看法。在许多研究中，面带微笑的人被认为比表情平静的人更友善、更有吸引力、更值得信赖。不过，这种效果并不是在哪里都一样：正如那项涵盖44种文化的研究所显示的，微笑并不总能让人显得更聪明。

At work, smiling has been linked to better results in job interviews and in sales, especially when the smile looks genuine. Researchers have also looked at politicians smiling in TV debates and at smiling profile photos on dating sites, but those results are mixed. A smile helps with first impressions, but its effect is smaller than many self-help books claim.

在工作中，微笑被认为与求职面试和销售中更好的结果有关，尤其是当笑容看起来很真诚的时候。研究者还考察过在电视辩论中微笑的政治人物，以及交友网站上面带笑容的头像，但这些研究的结论不一。微笑有助于给人留下良好的第一印象，但它的作用比许多励志类书籍所说的要小。

Babies smile from their first days, and ultrasound scans show smiles even before birth. These early smiles are called reflex or spontaneous smiles. They often appear during sleep and come from activity inside the brain, not from anything the baby sees. Social smiling, which means smiling in response to a face or a voice, usually begins at around six to eight weeks.

婴儿从出生后的头几天起就会微笑，超声波图像甚至显示胎儿在出生前就会微笑。这些早期的微笑被称为反射性微笑或自发性微笑。它们常常出现在睡眠中，源于大脑内部的活动，而不是因为婴儿看到了什么。社会性微笑，也就是对一张脸或一个声音作出回应的微笑，通常在六到八周左右出现。

Children who were born blind also smile when they are happy, even though they have never seen anyone smile. At the 2004 Paralympic Games in Athens, judo athletes who had been blind from birth made the same kinds of smiles as sighted athletes after winning or losing a medal match. This is strong evidence that the smile is something we are born with, not something we learn by watching others.

天生失明的孩子在开心时也会微笑，尽管他们从未见过别人微笑。在2004年雅典残奥会上，先天失明的柔道运动员在赢得或输掉奖牌争夺战后露出的笑容，与视力正常的运动员完全一样。这有力地证明了微笑是与生俱来的，而不是通过观察别人学会的。

A smile is a reaction to happiness, but it is also a message to others and a habit shaped by culture. It is one of the simplest movements a face can make, and scientists are still working out what it does to the person who smiles.

微笑是对快乐的反应，但它也是传递给别人的信号，是一种由文化塑造的习惯。它是人脸能做出的最简单的动作之一，而科学家至今仍在研究它对微笑者本人究竟有什么影响。

Some of the most quoted findings about smiling did not hold up when scientists tested them again, and others turned out to be smaller than the headlines said. What remains well supported is that the smile is very old, that we are born with it and that it is understood almost everywhere. It connects people quickly, often before anyone has said a word.

一些被引用最多的关于微笑的研究结果，在科学家重新检验时并没有站住脚，还有一些则被证明效果比新闻标题所说的要小。证据依然充分的是：微笑非常古老，是我们与生俱来的，而且几乎在任何地方都能被理解。它能迅速拉近人与人之间的距离，往往在谁都还没开口之前就已经做到了。