How animals do business

Abstract

The field of comparative behavioural economics investigates decisions about the acquisition and exchange of goods and services. It does so in both humans and other species on the assumption that the cognition and emotions involved have a shared evolutionary background. This preface roughly defines the field and reviews a few selected early studies and concepts to offer a taste of what economic behaviour means in relation to species other than our own.

This article is part of the theme issue ‘Existence and prevalence of economic behaviours among non-human primates’.

The father of modern economics, Adam Smith [1], once remarked that ‘Nobody ever saw a dog make a fair and deliberate exchange of one bone for another with another dog…' This may well be true, but Smith was wrong to think that animals never trade or that fairness is alien to them. Like many of his contemporaries, he underestimated the sociality of animals, believing that they do not depend on each other in the way we humans do. My guess, though, is that the Scottish philosopher would have been delighted to see how far the fledgling field of animal behavioural economics has come.

Valued goods move between owners all the time. In the same way that my office would not stay empty for long were I to move out, nature's real estate changes hands. Potential homes range from holes drilled by woodpeckers to abandoned burrows and nests. A typical example of such a ‘vacancy chain' is the housing market among hermit crabs. Each crab carries its house around—usually an empty gastropod shell—so as to cover its soft abdomen. The problem is that the crab grows. Hermit crabs are always on the look-out for larger accommodations. The moment they upgrade to a roomier shell, other crabs line up for the vacated one [2].

One can easily see supply and demand at work here, but since it plays itself out on a rather impersonal level it is not the barter or trade Smith had in mind. Hermit crabs are no deal-makers and in fact have no qualms evicting previous owners by force. Barter is present in the primates, though. It is suggested by reports on high-ranking male chimpanzees ‘bribing’ others by sharing meat selectively with their allies [3], or raiding papaya plantations of a nearby village to share the fruits overwhelmingly with fertile females [4]. A well-documented case is the work on temple macaques in Bali, Indonesia [5]. The monkeys snatch objects (e.g. smartphones, sunglasses) from tourists after which they patiently wait for a human food exchange proposal to trade in the stolen item.

It is hard to define economics, especially in relation to animals. Most definitions of human economics stress the production and distribution of goods and services, and the allocation of resources. Some go further and mention the maximization of profit or the minimization of cost, but this is merely a hypothesis about one of the objectives of economic activity. Many of the latest insights suggest, in fact, that human choices often violate the rules attributed to Homo economicus. Behavioural economics routinely questions assumptions behind rational choice theory [6]. Why do we have a sense of fairness that sometimes makes us forego advantageous resource distributions? Why does an aversion to loss exceed the desire to acquire novel items of equal value? These are not rational decisions, but emotional ones. Emotions bias our decisions in a way that may undermine the profit maximizing traditionally assumed by economists. As [7, p. 139] put it: ‘Much of the thrust of behavioural economics has involved, or at least could be construed as involving, an enhanced understanding of emotions.'

The emotional component of human economic decision-making provides a natural link to animal behavioural economics. Apart from the cognitive and learning processes that we share with many species, we also share emotions with them. Like them, we are first of all emotional beings [8]. It is often said that emotions reflect the wisdom of ages, because natural selection has shaped them to steer our decisions in adaptive directions. For example, in proposing his theory of reciprocal altruism, Trivers [9] explicitly included emotional processes, such as gratitude. It is not enough to remember the behavioural interactions with others, because favours will only be returned if the memory is coloured by positive feelings towards those who have helped in the past. Humans know this colouring as ‘gratitude,' which acts as the emotional lubricant of reciprocity. We have also learned that reciprocal exchanges in chimpanzees and vampire bats are not merely a matter of tit-for-tat, but that long-term bonding and ‘trust' figure into transactions [10,11]. These emotional biases are probably as important as rational calculations and have an evolutionary history older than our species.

The study of primate behavioural economics reviewed in this special issue seeks to reveal the psychology behind decisions about goods and services. As an example of what the field is about it is useful to mention a few classic studies. One of the first was the work by Wolfe [12] on token exchange by captive chimpanzees. The apes were trained to use differently coloured plastic tokens to obtain goods from a ‘chimpomat'. The investigators compared the tokens to ‘promissory notes', like money, while assigning different values to them [13]. Tokens could buy food but also favourite activities, such as a play session with the experimenter. The chimpanzees were willing to work for tokens, taking them as surrogate rewards.

Another early study proposed ‘respect of possession,' inspired by Kummer's fieldwork on the male–female bond in hamadryas baboons. In the animal kingdom there is often also, of course, disrespect of possession, when dominants take resources away from subordinates, which is why exceptions to the ‘right of the strongest' draw all the more attention. Baboon males respect each other's possession of females regardless of their hierarchy, i.e. a male who has proven to be dominant when two males approach the same resource is nevertheless inhibited from taking away a female once she has been claimed by another [14]. A follow-up study with food containers in a captive colony found that these baboons recognize each other's ownership and respect it, a tendency that according to the authors helps avoid fights when individuals feed in close proximity [15]. Many primates show similar inhibitions, which were explored in chimpanzees by measuring their response to a gradually dwindling resource. Instead of jostling and competing, the apes put their dominance relations aside and patiently waited for each other, taking turns while peacefully exploiting the resource [16].

Experiments inspired by fieldwork raise an important point, which is that of ecological validity. Are we testing for capacities that have meaning in the natural lives of animals? Whereas we may wonder whether the ‘chimpomat' relates to anything in the natural habitat of chimpanzees, studies of respect of possession or reciprocal exchange clearly do relate to natural life. After all, reciprocity has been studied extensively in both the field and captivity, and is considered one of the cornerstones of cooperative societies, such as those of the primates. Many primates live in groups because they derive benefits from each other's presence, which benefits may range from defense against predators to the finding and sharing of food [17].

From documenting reciprocity in alliances and food sharing, the field has moved to cooperation in general, and the pay-offs it yields. Experimental studies of cooperation have been inspired by an early cooperative pulling task in which two apes reached food by collectively pulling in a box that was too heavy for either one of them alone [18]. Using a similar paradigm, other studies have demonstrated the importance of partner choice and the need to reduce competition [19,20].

Out of the cooperation work grew studies of pay-off distribution and inequity aversion, which brought the primate work suddenly close to one of the favourite topics of human behavioural economists. For example, Brosnan and colleagues conducted experiments with capuchin monkeys that showed negative reactions to unequal reward distributions as well as improved cooperation when distributions were equal [21,22]. Whereas the monkeys show negative responses to being disadvantaged compared to a companion, chimpanzees go beyond this: the advantaged party may try to equalize the outcome. This prompted follow-up studies in which chimpanzees played the Ultimatum Game, a popular economics game. They showed the same preference for equal outcomes as 3- to 5-year-old human children tested in the same paradigm [23]. The ‘sense of fairness' of animals remains controversial, however. The inclusion of different experimental procedures and a greater variety of species have brought both support and raised new questions about the topic [24].

In primate societies, other individuals represent a resource that can deliver benefits such as grooming, food, or support. One way to look at social relationships is as investments in which partners both provide and take behavioural services [25]. The framework resembles one of supply and demand, which is what Noë and Hammerstein had in mind with their biological market theory [26]. This theory applies whenever partners can choose whom to deal with. It is a theory of resource availability and exploitation. An early example concerned babies as a resource for wild baboons. Female baboons are attracted to newborn infants, both their own and those of others. They invest time grooming the mother to be able to handle her infant. The amount of grooming performed is inversely proportional to the baby supply: mothers of rare infants are able to extract a higher price in grooming than mothers in a troop full of infants [27].

The above studies have in common that they concern the exchange of benefits and the ability to estimate their value. Value varies with the circumstances, and past exchanges play a role in future ones either via the route of memory and scorekeeping or via bonding and mutually positive emotions and attitudes. The first is known as calculated reciprocity, the second as attitudinal reciprocity, which is simpler and more widespread [28,29]. It has been proposed that the biases that underlie our economic choices have a long evolutionary history [30]. Purely based on observed behaviour, this is hard to confirm, however. It will always remain possible to come up with different explanations of how humans and other animals arrive at their decisions. This is where neuroscience and detail-oriented experimentation (such as eye-tracking studies) can make a contribution. Their inclusion in the present issue is commendable, therefore. Ideally, we would present both human and non-human primates with similar tasks and contingencies to find out not only if they arrive at similar choices, but also if they do so based on similar information and are affected by similar preferential biases. This is a major undertaking, but will be essential to convince economists that the processes they study have a long evolutionary background and can therefore be informed by research on other animals [31–33].

The present issue covers many topics that have until now progressed independently through the animal behaviour literature, sometimes with reference to human economics, but often in a different context. As yet, we lack a coherent synthesis of animal economic decision-making and its connection with human economics. To gather these contributions together is an excellent first step to create a new field, because I am convinced that a field of study it will become. It will be one that mixes evolutionary thinking, cognitive approaches, neuroscience and primatology. But let me hasten to add that there is no reason to consider the processes under study to be limited to the primates.

Data accessibility

This article has no additional data.

Competing interests

I declare I have no competing interests.

Funding

I received no funding for this study.