Do Monkeys Care What Is Fair?

作者：Katherine A. Cronin ?? Lydia M. Hopper? ?譯者：小婧視野?

ABSTRACT摘要

為了了解我們人類自身行為習慣的進化起源以及為了對其他靈長動物的行為有更深刻的理解，科學家們對人類、猿類和猴子的種群內公平性進行研究 。科學家研究發現，有時候猴子會選擇與同伴平等地分享食物，它們的選擇往往取決于它們屬于哪一個物種以及它們所處的具體環境。猴子會更愿意幫助同伴，但即便如此猴子也不會特意地按公平原則去行事的。此外，盡管猴子似乎能夠意識到結果的不公平，但它們似乎也僅僅是在得到的東西比別人少的時候才會擔心不公平，反之則并不擔心。

? ? 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?

我們為什么想知道猴子是否有公平感呢？

想象一下，你正在慶祝你朋友的生日，你和你朋友在一起共同烘烤了一個津津有味的蛋糕。你的朋友剛吹滅蠟燭，正在切蛋糕與客人分享。前三位客人都分到了大片的蛋糕，輪到你時卻發現蛋糕小到極致，你會有什么樣的感覺？這樣公平嗎？大多數人對“什么是公平”及“什么不屬于公平”有明確的認知，但這些認知是從哪來的呢？公平的大致概念是指人與人之間一視同仁，和付出后得到公平的回報。

? ? 為了了解我們人類自身行為習慣的進化起源以及為了對其他靈長動物的行為有更深刻的理解，科學家們對人類、猿類和猴子的種群內公平性進行研究 。通過研究一系列的靈長動物，科學家們便可開始了解公平是如何產生的。在這篇文章中，我們將討論猴子是否有公平感。為了更好地了解公平感在動物王國中是如何出現的，科學家們還研究與人類相距更遠的物種的公平性問題，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：公平往往意味著結果的平等

? ??設想你和你朋友在餐桌上發現了四顆糖果。你可能會拿起糖果，分享一塊給你朋友。這么做是很友好的！然而，你擁有了三顆糖果，而與此同時你朋友只有一顆，這樣做并沒有帶來結果的平等。公平起見，你需要分給你朋友兩顆糖，這樣你們倆都擁有兩塊糖了。在這種情況下，你的朋友會變得非常開心，因為他／她和你擁有的糖果的數量是一樣的。人們通常不喜歡自己得到的東西比別人少，這就是所謂的“厭惡不平等「當一個人對接受不同于其應得的獎勵作出消極反應時，通常表現為拒絕接受所提供的獎勵或拒絕進一步參與活動」（inequity aversion）”現象。

? ? 猴子的行為會帶來的平等的結果嗎？為了找出這個問題的答案，科學家們讓猴子選擇如何分配獎賞，這些獎賞通常是它們發自內心喜歡的小塊食物。科學家們要求一個猴子在兩個選項中做出自己的選擇——選項一是只給它自己一塊食物，選項二則是給附近的另一只猴子提供食物，同時這只猴子本身會得到同等的食物獎賞。如果猴子設法創造出平等的結果，它們應該會選擇既為自己也為其他猴子提供食物的那個選項。它們真的會這么選擇嗎？有時候這樣罷了。

? ? 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.

? ? ? ? ? ? 圖1: 測試猴子是否會做出他人也獲得獎賞的選擇。

·?????? (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）兩個托盤上都有食物，猴子可以選擇其中一個托盤。當猴子拉動一個托盤去獲取食物時，另一個托盤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.?

? ?（中間）左邊的猴子選擇了“我有一份你也有一份”的盤子，從而產生了公平的獎勵結果。

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

? ? （右）在這里，左邊的猴子選擇了只為自己提供食物的托盤，導致獎賞結果不公平

03

SPECIES AND FRIENDSHIPS INFLUENCE FAIRNESS

物種和友誼影響公平性

?猴子是否傾向于平等的結果似乎取決于這個猴子屬于哪一個物種（世界上有200多種猴子，到目前為止，科學家們已經對10幾種猴子的公平性進行了研究）。科學家們認為，解釋物種差異的一個說法是所謂的“合作哺育「親生父母以外的社會群體成員幫助撫養群體中的后代」”假說（cooperative breeders）。該假說推斷，像狨猴和絹毛猴這一類生活在家庭群體中，幫助養育不屬于自己的孩子的物種，會更加在乎公平性。在某些情況下，合作哺育的猴子會在實驗中選擇平等的結果，但并不是所有情況都這樣。此外，像卷尾猴這些非合作哺育的物種有時候也會做出平等的選擇，這么看來還有一些未知的東西需要探索。

? ? 還有什么有可能的因素會影響到猴子選擇平等的結果呢？似乎當一只猴子與另一只受益的猴子有深厚友誼時，猴子會更有可能選擇平等的結果。似乎當猴子看不到食物被分攤給別人的時候，就會更有可能做出平等的選擇。猴子和其他動物一樣，在看到偏愛的食物時會表現出異常興奮的樣子，所以，當食物陳列在它們面前時，讓它們做決定是很艱難的。為此，一些科學家們采用在觸屏電腦上顯示食物或使用食物的象征性代號（如代幣）的方式選擇食物。

? ? 總而言之，似乎有很多不同的因素會影響到猴子做出平等的選擇。然而，即使在猴子確實做出了平等選擇的情況下，它們似乎還比不上人類那樣會頻繁不斷地做出平等的選擇。那些揭示了猴子更喜歡平等選擇的科學家們甚至發現，哪怕在公平很重要的情況下，猴子們也不見得會經常做出這種公平的選擇。這可能意味著，猴子能夠意識到公平，也可以創造公平，但它們不會認為這一切都是至關重要的。

?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！努力重要嗎？

?讓我們回到前文所說分糖果的情景。如果你和你朋友手上都有兩顆糖果，這種情況我們認為是公平的又或者說是公正的。我們所關注的是結果的平等。但是，如果這是你通過在家做家務掙來的糖果呢？你朋友沒有做任何家務，卻和你一樣最終得到兩顆糖果，那這還是最公平的結果嗎？當然不是了，因為當人們在考慮“什么是公平”的時候往往會考慮到他們所付出的努力。可如果你和你朋友都做了家務，卻只有你得到了糖果呢？那也會顯得不公平。科學家們還考慮了猴子的選擇是如何受每只猴子的付出和收獲間的關系的影響。

? ? 科學家們已經研發了一種可以測試猴子是否會在意于同工同酬的研究方法。在這些研究中，猴子經過訓練后，通過與科學家們交換小塑料代幣來獲取獎賞。每當猴子與科學家交換一個代幣，就可以獲得一小塊食物。為了判斷猴子是否會對不公正「是一種不公平的結果，即一個人得到的回報與應得的不對等，如同工不同酬。」（同工不同酬）的現象作出反應，以及如何作出反應，科學家們會給其中一個猴子它們喜歡的食物（比如一根香蕉），而給另一只猴子它們不太喜歡的食物（比如一根胡蘿卜）。因此，盡管兩只猴子與科學家們交換同樣數量的代幣，但它們得到的獎賞卻不同。

?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.

?圖1: 測試猴子是否會做出他人也獲得獎賞的選擇。

?(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）兩個托盤上都有食物，猴子可以選擇其中一個托盤。當猴子拉動一個托盤去獲取食物時，另一個托盤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. （中間）左邊的猴子選擇了“我有一份你也有一份”的盤子，從而產生了公平的獎勵結果。

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

?（右）在這里，左邊的猴子選擇了只為自己提供食物的托盤，導致獎賞結果不公平。

如果猴子在得到它們不怎么喜歡的食物后拒絕繼續交換代幣或拒絕吃所給的食物，科學家們就可推斷：猴子對不公正的行為感到厭惡——它們意識到自己得到的食物比另一只猴子少，這樣是不公正的，它們就會了停止繼續與科學家們交換代幣。相比之下，如果猴子得到它們喜歡的食物后拒絕交換代幣或拒絕接受此食物獎勵，科學家便可推斷：猴子對優勢不公正「一種不平等的結果，即一個人做同樣數量的工作，得到的薪酬卻比別人多。（反義：劣勢不公正）」（advantageous inequity?）很敏感。（例如：同等的工作量卻能得到比其他猴子更多的報酬，這也是不公平的。）

? ? 科學家們用不同種類的猴子（如：獼猴、卷尾猴、松鼠猴、夜猴（也叫貓頭鷹猴）和狨猴）進行了這類實驗。就如前文所分享的研究所描述的一樣，這些研究也揭示了不同種類的猴子之間的差異。一般地，共同哺育的猴子（如狨猴）不會對不公正的行為現象做出反應。相比之下，其他猴子（如卷尾猴）則會對此做出反應：當它們發現在同等工作后與其他猴子相比得到的卻是自己不喜歡的食物時，它們會拒絕繼續工作／或拒絕所得到的食物。然而，猴子并不會對優勢不公正做出反應。也就是說，它們不會介意自己是否得到比別人更好的獎賞。

?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樣的呢？

?我們所討論的研究是在動物園和實驗室中進行的。但我們在野生動物的行為中看到了公平的證據嗎？在野外，我們想必看到過猴子們互幫互助的行為，例如：黑長尾猴會通過發出警報聲來提醒它們群體當心附近的捕食者，棉頂絹毛猴會鳴叫以提醒其他猴子發現了好食物，而狒狒會結盟，在戰斗中相互支持。但在其他情況下，我們看到猴子的行為是自私的，有時候它們甚至會為了確保自己獲得的利益最大化而爾虞我詐。從這些觀察結果來看，猴子們是否了解各自獲得的利益是多少，以及它們是否知道各自的勞動量是多少，這仍是一個迷。這就是為什么上文探討的實驗可以幫助科學家們了解公平在我們觀察的行為中到底起著多大的作用。

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?

結論

?歸根結底，猴子的公平感似乎沒有我們人類的公平感那么強，但通過研究猴子對公平的選擇，以及它們對不公平情況下所做出的反應，我們可以更深入地了解這些價值觀念是如何在人類中演變的。人們天生就對“我們為什么是這樣的”以及“我們與其他動物之間是否獨樹一幟”很感興趣。當我們去研究其他靈長動物，研究它們的思維是如何運作的，我們就能更深入的了解自己。我們還研究猴子，研究猴子是否會在意其他人得到了什么？它們認為什么是不公平的？這些反應是如何依賴于生物間的關系的？以及不同種類之間的猴子有何不同？這將有助于我們了解自然界，有時也能幫助我們更好地了解如何在人工馴養的情況下更好地照顧它們。

?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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