Do Monkeys Care What Is Fair?

作者：Katherine A. Cronin    Lydia M. Hopper   译者：小婧视野 

ABSTRACT摘要

为了了解我们人类自身行为习惯的进化起源以及为了对其他灵长动物的行为有更深刻的理解，科学家们对人类、猿类和猴子的种群内公平性进行研究 。科学家研究发现，有时候猴子会选择与同伴平等地分享食物，它们的选择往往取决于它们属于哪一个物种以及它们所处的具体环境。猴子会更愿意帮助同伴，但即便如此猴子也不会特意地按公平原则去行事的。此外，尽管猴子似乎能够意识到结果的不公平，但它们似乎也仅仅是在得到的东西比别人少的时候才会担心不公平，反之则并不担心。

    Scientists study fairness in humans, apes, and monkeys to understand the evolutionary origins of our own behavior and to better understand the behavior of other primates. Scientists studying monkeys have found that, sometimes, monkeys will share food equally with others, but their choices often depend on their species and the specific circumstances. Monkeys are more likely to help friends, but even then, monkeys rarely go out of their way to act fairly. Furthermore, while monkeys appear to recognize unfair outcomes, they only seem concerned by inequity when they receive less than others, not when they receive more.

WHY DO WE WANT TO KNOW IF MONKEYS HAVE A SENSE OF FAIRNESS?

我们为什么想知道猴子是否有公平感呢？

想象一下，你正在庆祝你朋友的生日，你和你朋友在一起共同烘烤了一个津津有味的蛋糕。你的朋友刚吹灭蜡烛，正在切蛋糕与客人分享。前三位客人都分到了大片的蛋糕，轮到你时却发现蛋糕小到极致，你会有什么样的感觉？这样公平吗？大多数人对“什么是公平”及“什么不属于公平”有明确的认知，但这些认知是从哪来的呢？公平的大致概念是指人与人之间一视同仁，和付出后得到公平的回报。

    为了了解我们人类自身行为习惯的进化起源以及为了对其他灵长动物的行为有更深刻的理解，科学家们对人类、猿类和猴子的种群内公平性进行研究 。通过研究一系列的灵长动物，科学家们便可开始了解公平是如何产生的。在这篇文章中，我们将讨论猴子是否有公平感。为了更好地了解公平感在动物王国中是如何出现的，科学家们还研究与人类相距更远的物种的公平性问题，例如大象和家犬。

    Imagine that you are celebrating your friend’s birthday. Together with a group of friends, you have worked together to bake and frost a delicious birthday cake. Your friend has just blown out the candles and is slicing the cake to share with all the guests. The first three guests are handed large slices of cake, and then it is your turn. You are handed a teeny-tiny, skinny slice of birthday cake. How would you feel? Is this fair? Most of us have a clear sense of what is fair and what is not, but where does this come from? Fairness is the idea that people are treated equally, and rewarded fairly for the effort they have put in.

    Scientists tend to study fairness in humans, apes, and monkeys to understand the evolutionary origins of this behavior. By studying a range of primate species, scientists can start to understand how fairness came about. In this article, we discuss whether monkeys have a sense of fairness. Scientists also study fairness in species even more distant from humans, such as domestic dogs and elephants [1], to better understand how fairness emerges in the animal kingdom.

02

SHARING YOUR CANDY: FAIRNESS OFTEN INVOLVES EQUAL OUTCOMES 

分享你的糖果：公平往往意味着结果的平等

    设想你和你朋友在餐桌上发现了四颗糖果。你可能会拿起糖果，分享一块给你朋友。这么做是很友好的！然而，你拥有了三颗糖果，而与此同时你朋友只有一颗，这样做并没有带来结果的平等。公平起见，你需要分给你朋友两颗糖，这样你们俩都拥有两块糖了。在这种情况下，你的朋友会变得非常开心，因为他／她和你拥有的糖果的数量是一样的。人们通常不喜欢自己得到的东西比别人少，这就是所谓的“厌恶不平等「当一个人对接受不同于其应得的奖励作出消极反应时，通常表现为拒绝接受所提供的奖励或拒绝进一步参与活动」（inequity aversion）”现象。

    猴子的行为会带来的平等的结果吗？为了找出这个问题的答案，科学家们让猴子选择如何分配奖赏，这些奖赏通常是它们发自内心喜欢的小块食物。科学家们要求一个猴子在两个选项中做出自己的选择——选项一是只给它自己一块食物，选项二则是给附近的另一只猴子提供食物，同时这只猴子本身会得到同等的食物奖赏。如果猴子设法创造出平等的结果，它们应该会选择既为自己也为其他猴子提供食物的那个选项。它们真的会这么选择吗？有时候这样罢了。

    Suppose you and your friend find four pieces of candy on the kitchen table. You might pick up the candy and share one piece with your friend. That would be very kind of you! However, you would still have three pieces of candy while your friend would only have one. This decision does not lead to equal outcomes. To be fair, you would need to give two pieces of candy to your friend so that you each have two pieces. Your friend would likely be happier in this case, because s/he would have the same number of pieces of candy as you. People typically do not like getting less than someone else; this is called inequity aversion「When an individual responds negatively to receiving a different reward than they deserve, typically shown by rejecting the reward they are offered or by refusing to participate in the activity further.」.

    Do monkeys behave in ways that lead to equal outcomes? To find out, scientists give monkeys choices about how to divvy up rewards, generally small pieces of food that they really like. Scientists will ask a monkey to choose between two options—one that provides a piece of food just to themselves, and another option that provides an equal reward to another monkey nearby, as well as to themselves (Figure 1). If monkeys are seeking to create equal outcomes, they would choose the option that provides a piece of food to both themselves and another. Do they? Sometimes. 

· Figure 1 - Test for whether monkeys prefer that others receive rewards, too.

            图1: 测试猴子是否会做出他人也获得奖赏的选择。

·       (Left) The monkey can choose either tray, both of which have food on them. When the monkey pulls one tray to get the food, the other tray is no longer accessible.

（左）两个托盘上都有食物，猴子可以选择其中一个托盘。当猴子拉动一个托盘去获取食物时，另一个托盘上的食物就不能再拿了。 

·       (Center) The monkey on the left has just chosen the tray gives food to both himself and the neighboring monkey, resulting in equitable rewards. 

   （中间）左边的猴子选择了“我有一份你也有一份”的盘子，从而产生了公平的奖励结果。

·       (Right) Here, the monkey on the left has just chosen the tray that provides food for himself only, resulting in inequitable rewards.

    （右）在这里，左边的猴子选择了只为自己提供食物的托盘，导致奖赏结果不公平

03

SPECIES AND FRIENDSHIPS INFLUENCE FAIRNESS

物种和友谊影响公平性

 猴子是否倾向于平等的结果似乎取决于这个猴子属于哪一个物种（世界上有200多种猴子，到目前为止，科学家们已经对10几种猴子的公平性进行了研究）。科学家们认为，解释物种差异的一个说法是所谓的“合作哺育「亲生父母以外的社会群体成员帮助抚养群体中的后代」”假说（cooperative breeders）。该假说推断，像狨猴和绢毛猴这一类生活在家庭群体中，帮助养育不属于自己的孩子的物种，会更加在乎公平性。在某些情况下，合作哺育的猴子会在实验中选择平等的结果，但并不是所有情况都这样。此外，像卷尾猴这些非合作哺育的物种有时候也会做出平等的选择，这么看来还有一些未知的东西需要探索。

    还有什么有可能的因素会影响到猴子选择平等的结果呢？似乎当一只猴子与另一只受益的猴子有深厚友谊时，猴子会更有可能选择平等的结果。似乎当猴子看不到食物被分摊给别人的时候，就会更有可能做出平等的选择。猴子和其他动物一样，在看到偏爱的食物时会表现出异常兴奋的样子，所以，当食物陈列在它们面前时，让它们做决定是很艰难的。为此，一些科学家们采用在触屏电脑上显示食物或使用食物的象征性代号（如代币）的方式选择食物。

    总而言之，似乎有很多不同的因素会影响到猴子做出平等的选择。然而，即使在猴子确实做出了平等选择的情况下，它们似乎还比不上人类那样会频繁不断地做出平等的选择。那些揭示了猴子更喜欢平等选择的科学家们甚至发现，哪怕在公平很重要的情况下，猴子们也不见得会经常做出这种公平的选择。这可能意味着，猴子能够意识到公平，也可以创造公平，但它们不会认为这一切都是至关重要的。

 Whether monkeys favor equal outcomes seems to depend on the species (there are more than 200 species of monkeys, and so far, scientists have studied fairness in about a dozen species). One idea that scientists have considered to explain species differences is the called the cooperative breeding「When members of the social group other than the biological parents help raise the offspring in the group.」 hypothesis.This hypothesis predicts that species, such as marmosets and tamarins, which live in family groups and help raise babies that are not their own, will be more tuned in to fairness [2]. In some cases, monkeys that are cooperative breeders choose the equal outcome in the experiment, but not all the time. Also, sometimes species that are not cooperative breeders, such as capuchin monkeys, make the equal choice, so there seems to be a bit more going on.

What else might be influencing whether monkeys seek equal outcomes? It seems like monkeys are more likely to make the equal choice when they have a good friendship with the other monkey who will benefit. It also seems that monkeys are more likely to make the equal choice when they cannot see the food they are divvying up. Monkeys, like other animals, get very excited by the sight of food they like, and have a harder time making decisions when food is in front of them. For that reason, some scientists have used touchscreen computers that show images instead of actual food items, or have asked monkeys to make choices using symbolic representations of food, such as tokens.

  All in all, a lot of different things seem to influence whether a monkey makes the equal choice. However, even in the cases where monkeys do make equal choices, they seem to do less frequently or consistently than humans do. Even scientists who have shown that monkeys prefer the equal choice find that the monkeys do not make that choice as often as they could if fairness was very important to them. This might mean that monkeys are capable of recognizing fairness, and creating fairness, but they do not think it is important all of the time.

04

BUT WAIT, DOES EFFORT MATTER?

且慢！努力重要吗？

 让我们回到前文所说分糖果的情景。如果你和你朋友手上都有两颗糖果，这种情况我们认为是公平的又或者说是公正的。我们所关注的是结果的平等。但是，如果这是你通过在家做家务挣来的糖果呢？你朋友没有做任何家务，却和你一样最终得到两颗糖果，那这还是最公平的结果吗？当然不是了，因为当人们在考虑“什么是公平”的时候往往会考虑到他们所付出的努力。可如果你和你朋友都做了家务，却只有你得到了糖果呢？那也会显得不公平。科学家们还考虑了猴子的选择是如何受每只猴子的付出和收获间的关系的影响。

    科学家们已经研发了一种可以测试猴子是否会在意于同工同酬的研究方法。在这些研究中，猴子经过训练后，通过与科学家们交换小塑料代币来获取奖赏。每当猴子与科学家交换一个代币，就可以获得一小块食物。为了判断猴子是否会对不公正「是一种不公平的结果，即一个人得到的回报与应得的不对等，如同工不同酬。」（同工不同酬）的现象作出反应，以及如何作出反应，科学家们会给其中一个猴子它们喜欢的食物（比如一根香蕉），而给另一只猴子它们不太喜欢的食物（比如一根胡萝卜）。因此，尽管两只猴子与科学家们交换同样数量的代币，但它们得到的奖赏却不同。

 Let us return to the candy scenario. We considered the situation to be equitable, or fair, if you and your friend each had two pieces of the candy. We focused on the results being equal. But what if you earned that candy by doing chores around the house? Is the fairest outcome still for you and your friend, who did not do any chores, to end up with two pieces of candy each? Probably not, because people tend to consider the effort involved when considering what is fair. What if you and your friend both complete chores, but only you get candy? That also would not seem fair. Scientists have also considered how monkeys’ choices are impacted by how much each monkey had to work for the rewards.

Scientists have developed a way to test whether monkeys prefer everyone to be paid equally for doing the same amount of work. In these studies, monkeys are trained to work for rewards by exchanging small plastic tokens with a scientist (Figure 2). Every time the monkey exchanges a token, it gets a small piece of food. To determine if, and how, monkeys respond to inequity「An unfair outcome in which one individual receives a different reward than they deserve, such as unequal pay for equal work.」, scientists have two monkeys take turns exchanging tokens. Each time, the scientist gives one monkey a food that monkeys really like (like a slice of banana) but gives the second monkey a less-preferred food (like a piece of cucumber). So, while both monkeys are working equally hard by exchanging tokens, they are rewarded differently.

•Figure 1 - Test for whether monkeys prefer that others receive rewards, too.

•图1: 测试猴子是否会做出他人也获得奖赏的选择。

•(Left) The monkey can choose either tray, both of which have food on them. When the monkey pulls one tray to get the food, the other tray is no longer accessible.（左）两个托盘上都有食物，猴子可以选择其中一个托盘。当猴子拉动一个托盘去获取食物时，另一个托盘上的食物就不能再拿了。 

•(Center) The monkey on the left has just chosen the tray gives food to both himself and the neighboring monkey, resulting in equitable rewards. （中间）左边的猴子选择了“我有一份你也有一份”的盘子，从而产生了公平的奖励结果。

•(Right) Here, the monkey on the left has just chosen the tray that provides food for himself only, resulting in inequitable rewards.

•（右）在这里，左边的猴子选择了只为自己提供食物的托盘，导致奖赏结果不公平。

如果猴子在得到它们不怎么喜欢的食物后拒绝继续交换代币或拒绝吃所给的食物，科学家们就可推断：猴子对不公正的行为感到厌恶——它们意识到自己得到的食物比另一只猴子少，这样是不公正的，它们就会了停止继续与科学家们交换代币。相比之下，如果猴子得到它们喜欢的食物后拒绝交换代币或拒绝接受此食物奖励，科学家便可推断：猴子对优势不公正「一种不平等的结果，即一个人做同样数量的工作，得到的薪酬却比别人多。（反义：劣势不公正）」（advantageous inequity ）很敏感。（例如：同等的工作量却能得到比其他猴子更多的报酬，这也是不公平的。）

    科学家们用不同种类的猴子（如：猕猴、卷尾猴、松鼠猴、夜猴（也叫猫头鹰猴）和狨猴）进行了这类实验。就如前文所分享的研究所描述的一样，这些研究也揭示了不同种类的猴子之间的差异。一般地，共同哺育的猴子（如狨猴）不会对不公正的行为现象做出反应。相比之下，其他猴子（如卷尾猴）则会对此做出反应：当它们发现在同等工作后与其他猴子相比得到的却是自己不喜欢的食物时，它们会拒绝继续工作／或拒绝所得到的食物。然而，猴子并不会对优势不公正做出反应。也就是说，它们不会介意自己是否得到比别人更好的奖赏。

 If the monkey getting the less-preferred food refuses to keep exchanging tokens or to eat the food it is given, scientists conclude the monkeys are averse to inequity—they are aware they are getting less than the other monkey, which is not fair, and they quit. In contrast, if the monkey getting the better food refuses to exchange or take rewards, scientists conclude that the monkeys are sensitive to advantageous inequity「An unfair outcome in which one individual receives more than other individual for doing the same amount of work (opposite: disadvantageous inequity)」. (for example, getting more than the other monkey for the same work, which is also unfair).

  Scientists have run these kinds of inequity aversion tests with a few different monkey species, including rhesus macaques, capuchin monkeys, squirrel monkeys, night monkeys (also called owl monkeys), and marmosets [3]. Like the sharing studies described earlier, these studies have revealed that there are differences across monkey species. Generally, monkeys that are cooperative breeders (such as marmosets) do not respond to inequity. In contrast, other monkeys (such as capuchins) do respond to inequity: when they are getting a less-preferred food than another monkey for the same work, they refuse to keep working and/or reject the food they are offered. Monkeys do not appear to respond to advantageous inequity, however. That is, they do not tend to mind if they get a better reward than others [4].

05

WHAT ABOUT WILD MONKEYS?

那野外的猴子又是怎样的呢？

 我们所讨论的研究是在动物园和实验室中进行的。但我们在野生动物的行为中看到了公平的证据吗？在野外，我们想必看到过猴子们互帮互助的行为，例如：黑长尾猴会通过发出警报声来提醒它们群体当心附近的捕食者，棉顶绢毛猴会鸣叫以提醒其他猴子发现了好食物，而狒狒会结盟，在战斗中相互支持。但在其他情况下，我们看到猴子的行为是自私的，有时候它们甚至会为了确保自己获得的利益最大化而尔虞我诈。从这些观察结果来看，猴子们是否了解各自获得的利益是多少，以及它们是否知道各自的劳动量是多少，这仍是一个迷。这就是为什么上文探讨的实验可以帮助科学家们了解公平在我们观察的行为中到底起着多大的作用。

The research we have discussed has taken place in zoos and laboratories. But do we see evidence of fairness in monkey behavior in the wild? We certainly see monkeys acting in ways that help each other out. For example, vervet monkeys give alarm calls to warn their group about nearby predators, cottontop tamarins chirp and alert others to the presence of good food, and baboons form coalitions to support each other in fights. Yet, in other contexts, we see monkeys acting selfishly and sometimes even deceiving one another to ensure they get the most for themselves [5]. Whether the monkeys understand the amount of benefits they each gain and the amount of work they each contribute is not clear from these observations. That is why the experiments discussed above can help scientists understand to what degree fairness plays a role in the behaviors we observe.

 06

CONCLUSIONS 

结论

 归根结底，猴子的公平感似乎没有我们人类的公平感那么强，但通过研究猴子对公平的选择，以及它们对不公平情况下所做出的反应，我们可以更深入地了解这些价值观念是如何在人类中演变的。人们天生就对“我们为什么是这样的”以及“我们与其他动物之间是否独树一帜”很感兴趣。当我们去研究其他灵长动物，研究它们的思维是如何运作的，我们就能更深入的了解自己。我们还研究猴子，研究猴子是否会在意其他人得到了什么？它们认为什么是不公平的？这些反应是如何依赖于生物间的关系的？以及不同种类之间的猴子有何不同？这将有助于我们了解自然界，有时也能帮助我们更好地了解如何在人工驯养的情况下更好地照顾它们。

 Ultimately, monkeys’ sense of fairness does not seem to be as well-developed as our own, but by studying monkeys’ preferences for fairness, and their responses to unfair situations, we can learn more about how these values evolved in humans. People are inherently interested in knowing why we are the way we are, and if we are unique from other animals. When we learn about other primates, and how their minds work, we learn more about ourselves. We also learn more about the monkeys—whether they pay attention to what others get, what they find unfair, how these responses depend on relationships, and how monkey species differ from one another. This helps us to understand the natural world, and can sometimes help us better understand how to care for them in captivity as well.

—the end—

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