Chapter 49
Evolutionary Psychology and Public Policy

Nicolas Baumard

Introduction

Human beings seem to be at once a feat of engineering and a miserable technological failure. People may recognize the face of someone they met in passing years ago, but forget the three-digit security code of the credit card and the email password that they use all the time. Sometimes people may be generous, generating flows of billions of dollars after a hurricane or contributing large fractions of their income to finance public goods. At other times, people may be selfish, focusing on their own careers, family, and friends, and having no empathy for others. People can be very patient, spending thousands of hours in training that yields benefits only after many years. Yet the same people may be unable to resist the temptations of junk food and whim purchases and find themselves, years later, overweight and without savings for their old age.

How can we make sense of these paradoxes? It is not enough to conclude that human nature is flawed, or that humans are simply “not that smart” or “not very generous.” They are sometimes incredibly intelligent or exceedingly generous, and sometimes incredibly stupid or desperately greedy. More importantly—to echo a popular presentation of behavioral economics—they are predictably intelligent and predictably stupid, predictably altruistic and predictably selfish. Their achievements and their failures follow certain patterns, which are specific to humans. Uncovering the logic behind these patterns can enable us to design better policies, policies that account for the built-in constraints of human nature (shortsightedness, greed, cognitive biases), while using its core features (generosity, endurance, natural social expertise) as levers to achieve goals that cannot be achieved using standard approaches.

Beyond the Contradictions of Human Behavior: Evolutionary Challenges and Psychological Mechanisms

This chapter is based on the idea that the logic of human behavior lies in the psychological mechanisms that produce it (Cosmides & Tooby, 1997; Pinker, 1997). In short, by understanding the mechanisms that constitute our nature and why they were selected by evolution, we will be able to make sense of the apparent inconsistencies of human behavior.

This approach differs markedly from the classical economic approach, which is based on a highly idealized view of human behavior rather than on the more realistic portrait painted by behavioral economists. But this psychological and evolutionary approach also differs importantly from the standard approach in behavioral economics. While behavioral economics aims to document the ways in which the behavior of Homo sapiens departs from that of Homo economicus, the aim of psychological and evolutionary approaches is to understand why modern humans differ from “economic man”: why they are both nicer and dumber than classical economics would have us believe, and more fundamentally, why sometimes they are kind and sometimes petty, sometimes clever and sometimes stupid.

For evolutionary psychologists, humans are neither smart nor dumb. Instead, they are adapted to certain situations that posed recurrent challenges in the environment they evolved in (known in technical terms as the “environment of evolutionary adaptedness”—and which, importantly, differs from one psychological mechanism to the next). From this point of view, people's failure to behave “efficiently” may not be due to intrinsically weak faculties, but rather to mismatches between the situations their brain has evolved to deal with and the specific situations that they actually find themselves in today. Put in another situation that more closely resembles the problems their ancestors solved, they may prove extremely capable indeed.1

From Homo economicus to Homo sapiens: Theoretical and Practical Implications

Comparing two visions of humans, homo economicus and homo sapiens, may seem like a rather theoretical exercise. But throughout this chapter, we will see that such theoretical differences can have important practical consequences (see Figure 49.1). For instance, while the evolutionary and psychological approach agrees with the behavioral approach that humans are “dumber” than they are assumed to be in the classical model, in the evolutionary approach they are not understood to be dumber in general. Instead, humans are assumed to have evolved specific mechanisms to deal with the challenges that they faced in their environment. True, they sometimes seem unwise, but this is not because their capacities are intrinsically weak. It is because their brain is wired to solve certain types of problems—interacting in a small-scale society, choosing the most caloric food, or saving for the future without the help of the state or financial markets—but not all the problems that people typically face in a modern industrialized society, such as saving for retirement, understanding medical statistics, or refraining from eating too much fatty food.

Figure 49.1 Theoretical Differences and Their Consequences

From an evolutionary perspective, each problem is different and requires different solutions. Building a supercomputer that can solve any kind of problem would be enormously costly, and probably much less efficient. It is better to build lots of small devices specialized for specific tasks (eating, mating, detecting dangers, etc.). The downside of such a strategy is that sometimes, particularly when the environment changes quickly, these devices become less adapted to the challenges facing individuals. The job of an evolutionary and psychological perspective is precisely to help us better understand these situations.

So why we are so good at remembering faces and so bad at remembering credit card codes? Is it because we are irrational? Is it because our brain is suboptimal? More likely, it is because our brain was designed by evolution to deal with particular challenges. We are sometimes very smart—when a task is similar to one that our ancestors faced, like the challenge of recognizing a friend—and sometimes very dumb, when the task does not correspond to such an evolutionary challenge, like reading a text. The evolutionary psychological approach allows us to understand what cognitive constraints need to be taken into account when choosing a policy in a given context: The further away its goal is from the challenges that evolution adapted humans to facing, the harder it will be to implement.

Having brains specialized in performing specific tasks is not just an unfortunate constraint, however. It also means that we can use our very well-designed adaptations to develop new “tricks.” For instance, although learning how to read is difficult, painful, and slow, learning how to use smileys only takes a few seconds, because smileys tap into our face processing skills. In contrast to letters, we can use and remember dozens of smileys very quickly and effortlessly. More generally, marketing research has shown that using images rather words is a more efficient communication strategy, because faces, objects, and colors are more attractive and natural to humans than written words. Human nature can be both a constraint and a lever.

Why Sometimes Generous and Sometimes Greedy?

One puzzling aspect of human nature is how variable the tendency to cooperate seems to be. On one hand, humans appear to be far more generous than other animals. On the other hand, they often seem to be motivated only by selfishness. This creates important problems for policy design, because these contrasting aspects of human nature seemingly entail opposite policies. If people are greedy, then ensuring cooperation and protecting public goods always require very costly enforcement mechanisms. But if people are very generous, policies need to focus on inspiring generosity rather than on monitoring treacherous behavior.

How can we make sense of the apparent inconsistency of human cooperation? Here again, the solution lies in understanding the evolutionary challenges that humans faced in their ancestral environment. During most of human history, humans lived without institutions and the rule of law (Diamond, 2012; Hoebel, 1954). There were no state, no police, and no courts. This means that cheaters could take advantage of cooperative situations. Because they could not be sent to jail or even fined, honest cooperators ran the risk of being exploited: They might pay the cost of cooperation, while their partners could take the benefits and never pay them back.

On the surface, these conditions seem very detrimental to cooperation. If people can cheat without facing punishment, their best strategy should be to defect as often as possible, as in the famous Prisoner's Dilemma. And this is indeed what classical economic models predict. Fortunately, humans lived in a more complex environment than the prisoners of the dilemma. They could choose their partners. If someone cheated, they could always walk away and choose someone better to cooperate with (Aktipis, 2004; Baumard, 2010; Kaplan & Gurven, 2005).2

When partner choice is possible, being good becomes advantageous: By cooperating, you send others a signal that you are a good cooperator, and you attract good partners. The possibility of choosing partners and the consequent competition among individuals to be chosen as a partner by others made it possible for cooperation to emerge (Roberts, 1998; Baumard, André, & Sperber, 2013). Cheaters were not punished by external institutions, but ultimately they were punished nevertheless, because in time fewer and fewer people would cooperate with them.

This evolutionary approach explains the apparent inconsistency of human cooperation. In reality, people are not inconsistent cooperators—they are conditional cooperators (Trivers, 1971). Their strategy is the following:

• If others cooperate, they cooperate (otherwise they run the risk of being seen as a cheater).
• If others do not cooperate, they do not cooperate (otherwise they run the risk of being exploited by cheaters).

This conclusion has important consequences for policy design. It means that others' behavior is crucial: People are ready to abide by a social norm if they believe that others do the same. By contrast, if they think that they are the only ones who are complying with the norm, they are likely to stop respecting it. Similarly, this conclusion entails that trust is paramount: People are willing to cooperate a lot if they think that others are also honest cooperators. On the other hand, if they think that others are dishonest or lazy, they might stop contributing to the common good. A third consequence is that reputation can be a strong incentive in motivating people to cooperate. Finally, we will see that the evolutionary approach explains why fairness is so important to people and why, as a large number of empirical studies have shown, fairness is a prerequisite for any public policy.

Social Norms Matter

Two experiments illustrate the importance of the behavior of others in promoting or hindering cooperation. In the first, scientists compared two ways of asking clients to reuse their towels in a hotel. In half of the rooms, they left a card saying:

HELP SAVE THE ENVIRONMENT

You can show your respect for nature and
help save the environment by reusing
your towels during your stay.

In the other half the card said:

JOIN YOUR FELLOW GUESTS IN HELPING TO SAVE THE ENVIRONMENT

Almost 75% of guests who are asked to participate
in our new resource savings program do help by
using their towels more than once. You can join your
fellow guests in this program to help save the
environment by reusing your towels during your stay.

Results showed that the second card increased the number of clients who reused their towels by 25% (Goldstein, Cialdini, & Griskevicius, 2008).

The second experiment studied the impact of messages stuck to the doors of a middle-class neighborhood in San Marcos, California. These messages all asked people to use fans rather than air conditioning, but various reasons were given: One group was told that using fans would allow them to save $54 per month in electricity, another was told that the change would prevent the release of more than 100 kilos of greenhouse gas, another read that this was the most socially responsible option, and a final group was told that 77% of their neighbors were using fans rather than air conditioning, and that therefore this practice was the “choice of your community.” The reading of electricity meters showed that the first three conditions had very little or no impact on people's behavior. The last one, however, led to a 10% decrease in electricity consumption (Nolan, Schultz, Cialdini, Goldstein, & Griskevicius, 2008). In other words, people are happy to save the environment if they think others are doing it as well!

These results have obvious implications for policy design. Take the efforts of the U.K. government's Behavioural Insights Team (BIT), which is testing the efficiency of different messages in motivating people to pay their taxes. To do so, the BIT sent letters to 140,000 taxpayers. Residents received either a control letter (which contained no information about the behavior of others) or one of a number of different messages containing information about others' behaviors.

All of the social norm letters contained the statement that “9 out of 10 people in Britain pay their tax on time,” but some also mentioned the fact that most people in the recipient's local area, or postcode, had already paid.

The results revealed a 15 percentage point increase of tax payment relative to the control letters (see Figure 49.2). Moreover, the more local the information was, the bigger its impact on taxpayers. Overall, the U.K. tax authority estimated that this effect, if the same procedure were rolled out and repeated across the country, could lead to the payment of about £160 million in tax debts to the Exchequer over the 6-week period of the trial (Behavioural Insight Team, 2012). As this example shows, understanding the conditional logic of human cooperation can be a great lever in improving fiscal policy.

Figure 49.2 Percentage of Late Payers Who Had Responded After 3 Months

Trust Matters

The conditional logic of cooperation means that trust is paramount in social interactions. In the same way that people do not want to be seen as cheaters (and thus cooperate if they think others are cooperating), they do not want to be cheated on (and thus are less likely to cooperate if they don't believe that others are doing so). In line with this idea, empirical data show that trust has an important impact on both economic development and generosity (Putnam, 2000; Uslaner, 2002). Economic exchanges are more difficult and riskier when people do not trust each other, and as a result low-trust countries tend to have lower GDP (Fukuyama, 1995). Similarly, it makes less sense to help your neighbors if you believe that they are not likely to reciprocate, and as a result, people help others less in low-trust countries (Willinger, Keser, Lohmann, & Usunier, 2003).

Trust not only affects economic exchanges and informal interactions, it also greatly influences public policies (Algan & Cahuc, 2006). Indeed, any kind of policy is likely to be sensitive to free riding. For example, many benefits are conditional on behaviors that are not easily observable, such as living together as couples, having income other than unemployment benefits, or suffering from some illness. As marital status, black market work, and health are not easy for public bureaucracies to observe, cheating can be relatively easy, and policies can only work if people refrain from doing it (Bjørnskov & Svendsen, 2012). Consequently, because they are conditional cooperators, people are likely to vote for welfare policies only if they think that others are going to respect the law.

In line with this idea, it has been observed that levels of trust largely explain differences of opinion on the welfare state in different countries. For instance, the United States and Europe differ greatly in the level of social benefits offered through the state. This divergence is often thought to be related to cultural differences in attitudes on the role of the state. Further analysis, however, reveals that Americans think that the welfare state has an important role to play. Seventy-one percent of Americans think that it is either an “essential” or an “important” responsibility of government to ensure that everyone who wants a job has one, and 78% of Americans think that providing good medical care is an “essential” or “important” government responsibility, while 81% think the government should provide adequate housing (Alesina & Glaeser, 2004).

The real cultural difference occurs not at the moral level (“Should the government help the people?”) but at the level of trust. Indeed, Americans, just like Europeans (and humans everywhere), are conditional cooperators. They agree to help others, but only if others are good cooperators. In a modern state, this means that they agree to help others only if others work hard to get a job and contribute to the common good. However, Americans, in contrast to Europeans, have a very negative view of the poor. Indeed, while 60% of Europeans believe that the poor are trapped in poverty, only 29% of Americans agree with this idea. Similarly, 54% of Europeans think that luck determines income, compared to 30% of Americans. And while only 26% of Europeans think that the poor are lazy, 60% of Americans think so. In other words, both Americans and Europeans are happy to see the government help the poor if they believe that the poor deserve that help. However, Americans are much less likely than Europeans to believe that they do.

Statistical analyses suggest that this lack of trust has an important impact on the ability of the state to fund welfare programs to alleviate poverty. Indeed, both among U.S. states and European countries, the belief that luck determines income correlates with the level of social welfare spending. This contrast is all the more striking given that in reality, the level of social mobility is very similar on the two sides of the Atlantic (and if anything, mobility is slightly higher in Europe than in the United States). In other words, there is not so much differences between the American poor and the European poor. The poor in the United States are no lazier than those in Europe. What is detrimental to the establishment of public policies in the United States is thus not a general opposition to government intervention, but the cultural belief that others (and especially the poor and members of minorities) cannot be trusted. In the end, this state of mistrust prevents the investment of trillions in public policies and the development of effective poverty reduction policies.

In summary, trust is a central element for any policy. Because humans are conditional cooperators, they will be reluctant to cooperate, contribute to the public good, or help others if they think that others are not similarly well-intentioned.

Reputation Matters

Another consequence of the human propensity for conditional cooperation is that reputation is very important. In an environment where there are no institutions, reputation is an important guarantee that your partner is going to cooperate with you. If someone cheats, they lose their reputation as a good partner and thereby greatly decrease their chances of finding good partners in their turn. This explains why people spend so much time gossiping, telling stories and exchanging strategic information about others. Reputation is one of the most important resources that an individual has in life. A good reputation can make a career, and a bad reputation can end it.

Public policies can easily make use of people's desire to protect their reputation. For instance, psychologists have observed that people are less likely to respond to a letter sent by a company than by a named individual working in the very same company. A U.S. study tested the impact of Post-it notes and handwriting on people's likelihood of completing a survey (Garner, 2005). When the survey was accompanied by a handwritten Post-it note requesting completion, three quarters of recipients completed it, compared with half when the handwritten message was directly on the cover page, and just over a third of those who received the survey and cover page with no handwriting. In addition, those who responded to the handwritten Post-it note returned the survey more promptly and gave more detailed answers. When the experimenter added his initials and a “Thank you,” response rates increased even further (see Figure 49.3).

Figure 49.3 Response Rate to Survey When Testing a Handwritten Message

Getting people to commit is another way to increase cooperation. When people sign a document indicating that they will do something, they put their reputation more clearly on the line, because it is harder to plead ignorance in this case (Cialdini, 1993). In line with this idea, psychologists have found that that moving a signature box from the end of a form to the beginning can help promote more honest responses. Here, again, a psychological and evolutionary approach can help to make sense of apparently irrational behaviors. Why would adding a Post-it or moving a signature to the top of a letter increase cooperation? From a standard economic point of view, nothing has changed: The individual is still interacting with a large institution, and the incentives are the same (e.g., fees for late responses). But from a psychological and evolutionary perspective, paying attention to the person who sent the letter makes sense. Humans evolved in an environment where personal relationships were crucial for survival. They are equipped with a range of psychological mechanisms aiming at dealing with questions of reputation. Thus, they treat everything that puts their reputation at stake very seriously (Barclay, Chapter 33, this volume). Failing to consider social signals could compromise their reputation and the associated social benefits.

Humans are wired to pay attention to eyes, because the gaze can carry a great deal of relevant information: what others want, what they think, and also whether they are watching you. In a famous experiment, Gregory Bateson and his colleagues showed that this works in mostly automatical and unconscious fashion (Bateson, Nettle, & Roberts, 2006). In their experiment, they measured the amount of money that people put in a box to pay for milk at an unattended coffee machine. Every week, they alternated the image displayed on the wall above the box: either a pair of eyes or some flowers. They found that people put more money in the box when there was a pair of eyes rather than a picture of flowers on the wall above it. This is totally consistent with both people's motivation to project a good image of themselves and with their strong sensitivity to faces, and eyes in particular. The eyes on the wall activate mechanisms whose aim is to manage reputation. When people are alone in the room, parts of their brain (the mechanisms dedicated to reputation management) “believe” that they are actually being observed and that their reputation is at stake (see also Ernest-Jones, Nettle, & Bateson, 2011; Haley & Fessler, 2005).

Why are People Sometimes Patient and Sometimes Impatient?

In standard economic models, the aim of rationality is to maximize the fulfillment of preferences. The preferences themselves remain a given: They cannot be rational or irrational. But many human behaviors seem to reveal inconsistencies between their preferences: People want to enjoy ice cream, but do not want to gain weight; they want to buy fancy clothes, but also to save for their retirement; they would like to have a long life, but they smoke, drink, and refrain from exercise.

How can we make sense of these behaviors? Many economists have argued that humans just suffer from some sort of weakness of will. However, this idea seems to conflict with the many situations in which humans display extraordinary self-discipline, such as in courtship, parenting, or athletic training. Why is it that people are sometimes able to carry out long-term projects despite their short-term costs, while other times they fail completely?

Here again, an evolutionary perspective can make sense of an apparently contradictory pattern. Indeed, from an evolutionary perspective, not all goals are equally relevant (Cosmides & Tooby, 2013). Some goals, like raising a child, seeking social status, or eating sugary food are evolutionarily relevant (earlier humans with these goals had children who thrived, they had higher status and thus access to more resources, and they ate food that contained more energy). This means that, on average, individuals endowed with these “tastes” survived better over the generations than those who weren't.

By contrast, other goals, like saving for retirement or paying the bills, are almost totally irrelevant to the situations that faced our ancestors, and are experienced as either painful or boring. The evolutionary reason for this is obvious. For most of their history, humans lived in small groups of hunter-gatherers. In these small societies, there were no institutions, no market, no social security, and so on. The best way to save resources for the future was thus not to put these resources in a bank account or even to stockpile them (most resources were perishable), but rather to build a strong social network of friends and allies ready to extend help in case of illness, danger, or scarcity (Kaplan, Hooper, & Gurven, 2009). As Steven Pinker says:

How can I store extra food in the fat weeks and draw on it in the lean weeks? Refrigeration is not an option. I could gorge on it now and store it as a bubbler, but that works only up to a point; I can't eat enough in a day to avoid hunger for a month. But I can store in the bodies and mind of other people, in the form of a memory of my generosity they feel obliged to repay when fortunes are reverse. (Pinker, 1997, p. 555)

In line with this idea, people spend an enormous amount of time seeking friends, cultivating their friendships, and exchanging gossip about their friends. We experience these things as highly rewarding because over the generations, humans who liked having friends fared better than others. By contrast, despite their huge impact on people's lives, many aspects of modern life (saving for retirement, paying the bills, receiving medical treatment) are felt as a burden and are often forgotten or neglected (Burnham & Phelan, 2012).

The evolutionary and psychological approach allows us to understand when humans are able to carry a long-term project through—when it is evolutionarily relevant and they are thus equipped with adequate motivation—and when they fail—when it is not evolutionarily relevant and people therefore tend to lack motivation. At first sight, this analysis seems like bad news. It means that the goals of some public policies are going to be enormously difficult to achieve, and people will clearly need a nudge. Nevertheless, this aspect of human psychology needs to be taken into account. In recent years, many government agencies have started using new technologies to distribute such nudges, for instance by sending text messages to people on their cell phones to remind them to pay their bills (Datta & Mullainathan, 2012). Indeed, while people rarely need to be reminded that they have a date with an attractive partner or that they need to pick up their kids (evolutionarily relevant goals), they definitely need reminders for most of their administrative duties (evolutionarily irrelevant goal).

Similarly, because people lack motivation to fill in tax forms, agencies have started prepopulating all the fields to alleviate the burden. A U.S. study on the Free Application for Federal Student Aid found that prepopulating the form with information already held by the system and streamlining the process involved in completing the form significantly increased submission rates and college entry (Bettinger, Long, Oreopoulos, & Sanbonmatsu, 2012). This is result is all the more interesting given that in a sense, students clearly have an interest in completing the process. Yet because completing a form is psychologically irrelevant to the situations that shaped human nature, they still need some help.

To sum up, the evolutionary perspective may help to understand the limits of traditional public policies and the power of choice architecture (setting the default choices right in an administrative scheme). Traditional public policies assume that people are rational and that the only reason they take bad decisions is that they are ill-informed or not incentivized enough. Indeed, why would one prefer to have less money than more money? But the reality may be pretty different, because human have not evolved to maximize their saving account or their electricity bills. In consequence, they may not be interested at all in thinking about their retirement scheme or in paying their bill on time, which does not make any sense form a standard rational choice perspective. Understanding human cognition, and the context in which it evolves, may help designing policies that consider that human behavior is not irrational, but just ill adapted to modern societies, and that nudging people by changing the default choice in their retirement scheme can have way more impact than incentivizing their decisions or providing more information. For instance, a recent study on the Danish retirement system has shown that giving people money has less impact on their decision than just changing the default option (Chetty, Friedman, Leth-Petersen, Nielsen, & Olsen, 2013). In other words, because people do not care very much about their retirement plan, money cannot work as a good tool. Better use the power of nudge!

Living, Fast and Slow

From an evolutionary perspective, humans do not suffer from a general weakness of will or lack of patience. They are sometimes very patient, and sometimes totally impatient. The explanation for this apparent inconsistency lies in the evolutionary history of the human species and the psychological mechanisms that were selected over the course of this history. Thus, humans are typically very strong when it comes to investing in their social network, finding a mate, or raising a child, but much weaker when it comes to saving for retirement, refraining from eating fat, or exercising to burn extra calories.

Understanding the evolutionary and psychological basis of human preferences is crucial. If we just stick to general behavioral explanations without examining the specific situations that are associated with different kinds of behavior, we may draw mistaken conclusions. Witnessing people's weak willpower in their daily lives, for example, we might think that humans cannot be trusted when it comes to long-term projects. But when we use evolutionary thinking to sharpen our focus on the conditions on this apparent weakness of will—seeing how it is present in some domains of human life, but absent in others—we find that only evolution can explain the underlying logic of this variability.

The evolutionary perspective also allows us to explain another apparent paradox: Why is it that people from different social backgrounds have different preferences? From an economic perspective, it might seem that people with a lower socioeconomic status should be particularly cautious about saving, they should invest a lot in schooling to have better opportunities, and in general they should take fewer risks. But in reality, people in less advantaged positions tend to save less, invest less in education, have children sooner, and take more risks (Nettle, 2010a).

This paradox is not specific to humans. All organisms face fundamental trade-offs when deciding how to allocate limited resources. For example, all multicellular organisms need to choose between reproducing now or later, between investing in a few children or having a large family, or between taking small risks (and obtaining small amounts of resources) and taking large risks (and getting either large amounts of resources, or nothing, or worse).

A part of evolutionary biology known as “life history theory” addresses how organisms allocate limited resources to maximize fitness (Roff, 2002; Stearns, 1992). Life history theory provides a framework for understanding people's patterns of decisions about trade-offs in very diverse areas, from investments and health to education and sexual behavior (Ellis, Figueredo, Brumbach, & Schlomer, 2009; Griskevicius et al., 2013; Nettle, 2010b). In particular, it describes these strategies along a slow-to-fast continuum (Chisholm et al., 1993; Griskevicius et al., 2013; Nettle, 2010b) (see Figure 49.4). At the physiological level, faster and slower strategies are respectively associated with earlier and later physiological development and sexual maturity. At the psychological level, fast strategies are associated with short-term opportunism and taking immediate benefits with little regard for long-term consequences, whereas slow strategies are associated with long-term planning and delaying gratification to increase future payoffs.

Figure 49.4 Illustration of Correlates of Fast and Slow Life-History Strategy

Empirical studies show that, contrary to what might have been predicted from a standard economic point of view, harsher and poorer environments lead people to enact faster strategies, speeding up the timing of their physiological development and sexual maturation. This is because harsher environments are inherently more risky. As a result, organisms cannot expect to live as long as in a safer and richer environment. To increase their fitness, it is better for them to do less long-term investing, because their prospects of getting to reap the benefits of such investments are relatively poor. Similarly, they are better off reproducing as soon as possible, because the more they wait, the more they run the risk of dying or being injured or too poor to reproduce. Because harsher environments are less predictable, the best strategy is to take more risks and have more and earlier offspring. When the environment is more predictable, on the other hand, slower strategies associated with delaying reproduction and investing in future outcomes become adaptive. In line with life history theory, cross-cultural studies show that in environments characterized by higher mortality, people tend to have their first child at an earlier age. They also mature earlier, take more risks, and are more impulsive (Griskevicius et al., 2013; Nettle, 2010a).

From an evolutionary perspective, the faster strategies adopted by people living in harsh conditions are not irrational. Quite the contrary: In these contexts, they make perfect sense. The function of these behavioral strategies is to increase the chances of the organism to successfully reproduce itself despite a higher risk of death, injury, or accident. This does not mean, of course, that these mechanisms are always adaptive. Again, they evolved in a specific environment, in which there were no higher education, job markets, bank accounts, or policemen. It might be that today, they lead people to overreact to harsh environments in the same way that we overreact to the abundance of fat and sugar. If this is true, poor people may take too many risks, invest inadequately, and reproduce earlier than serves their interests or those of their children. The important point to understand, though, is that their decisions are not due to cognitive limitations or weakness of will. Instead they result from strong, context-sensitive feelings, which reflect evolutionary psychological adaptations aimed at allowing people to make the best trade-offs in a given type of environment.

From a policy perspective, this distinction is crucial. It means that people in lower socioeconomic strata might not need more information (about the advantages of saving or going to the health center, say). Increasing people's time horizon, for instance, may have drastic and long-lasting effects on people's preferences, without any need for change in their explicit beliefs.

Implications for the Goals of Development Policies

Evolutionary psychology not only explains why some policies are aligned with human psychology and others are not—it also gives us insights into what public policies should aim for. In other words, it is relevant both to the means by which development policies are pursued and their goals. Indeed, as we have seen throughout this chapter, human psychology—its cognitive systems, its heuristics, its reward systems—has been designed to fulfill certain goals, such as taking in energy-rich foods, avoiding pathogens, attaining social status, having friends and mates, and so on. That is why humans universally like sugar and fat; enjoy sex, parenting, and friendship; and seek social status and material resources.

This evolutionary perspective has profound implications for development policy. Policy makers often accept classical economic models, which hold that increasing income is the most efficient way to promote well-being. This “blank slate” approach is often preferred because it is supposed to be ethically neutral: Since there are many ways to be happy, this line of thinking goes, people should be left to choose which best fits their preferences. However, “maximum GDP” is not in fact a neutral measure. It assumes that money is always to be preferred to other kinds of goods, but this assumption does not hold from an evolutionary perspective. First, money—and more generally, cash economy—is a recent invention, and only appears a few thousand years ago. Second, although money can help us to achieve one kind of fitness-relevant goals, from an evolutionary perspective, many other goals such as children, friends, autonomy, dignity, and security also matter. Yet, most of the time, money cannot buy friendship, children, or security, and often maximizing GDP is actually detrimental to achieving these goals, as when increasing working hours and focusing on one's career translates into less time with friends and family and more stress.

Although the limits of maximum-GDP policy may seem more relevant in developed societies than for poorer ones, research on newly developed societies such as China suggest that development policies should take these effects into account in those cases as well. In the past 20 years, China has seen its GDP increase massively. But this increase has been associated with population movements, family breakdown, high unemployment, lack of solidarity, and higher inequality. In line with theoretical and empirical studies in psychology, this increase in GDP has been accompanied by a decrease in the reported well-being of most of the population, although it has risen somewhat at the upper end of the socioeconomic scale.

These empirical studies therefore raise a very important question: What is the point of developing the economy if all the benefits of a higher income come at the cost of higher levels of job-related stress, a shorter amount of time spent with family and friends, and decreases in self-esteem due to growing inequality?

In this last section, I review some parameters that are often undervalued or disregarded in development policy, and explain why, from an evolutionary perspective, they are crucial for well-being. Basically, what makes us happy is being in conditions that allow us to fulfill the goals that were important in environments of evolutionary adaptedness.

Absolute and Relative Income

A priori, maximizing GDP seems to be the most reasonable solution. Since, as is well known, money can buy everything, people will be better off with a higher GDP, whatever it is that they want. This idea, however, neglects the fact that humans are a special species. They live in groups, and their success in life depends on their position in their society. During most of human history (including the most egalitarian societies, such as those of hunter-gatherers, both ancient and modern), higher status has translated into more resources, more friends, more mates, more children, better health, and so on. In other words, fitness is highly correlated with status. This is the reason why people care a lot about their status and how well they fare in their society. It is a signal of their success as well as an end in itself, because it opens the way to a better life.

Because status is a good in itself, humans have evolved psychological mechanisms to evaluate their status and make it a reward in itself. For instance, brain imaging studies have demonstrated that social comparison activates brain areas associated with rewards, like the striatum. Doing better than others is intrinsically rewarding for humans. Conversely, doing worse than others is intrinsically painful.

Humans are so obsessed by social comparison that it is difficult to overestimate the importance of social status. A range of studies suggest that above a certain level of affluence, people care more about social comparison than absolute level of resources (Frank, 1985, 2007). In a famous experiment (Solnick & Hemenway, 1998), participants were given the choice to live in either situation A or situation B.

Situation A: Your current yearly income is $50,000; others earn $25,000.

Situation B: Your current yearly income is $100,000; others earn $200,000.

Participants were told that the prices were what they were currently and that therefore the purchasing power of money was the same in situations A and B. Despite the participants' 100% increase in income between society A and society B, many said they would prefer to live in society A because in this scenario they fare better than others.

The importance of social status has fundamental consequences for the organization of society. It means that, everything else being equal, it is better to live in a more equal society (Frank, 2007; Wilkinson & Pickett, 2008). Indeed, on average, because social status is a zero-sum game, the more unequal the society is, the less happy people will be. Note that this holds even for the richer part of the society, because people compare themselves to those who are closer to them—and the more unequal the society, the greater the distance between people, even among those with the highest incomes.

In line with this idea, epidemiological studies show that inequality has adverse effects on humans in a range of domains, such as trust, mental illness, life expectancy, infant mortality, obesity, educational performance, teenage motherhood, and homicide (see Figure 49.5). What is striking is that this effect cannot be explained by absolute income (through a link between a relatively low income and a relatively high level of inequality). Among developed countries, absolute income does not seem to play an important role in preventing social and health problems. The richest countries, such as the United States, are not specially immunized against homicide, teen pregnancy, or obesity. And the poorest, like Greece, New Zealand, and Spain, are not especially more prone to these problems. The main predictor of rates of obesity, teen pregnancy, or homicide is the level of inequality in a society.

Figure 49.5 The effect of inequality (bottom) on health and social problems in developed countries. Income inequality is measured by the ratio of incomes among the richest 20% to those of the poorest 20% in each country.Income inequality is measured by the ratio of incomes among the richest 20% to those of the poorest 20% in each country. Source: From Wilkinson and Pickett, 2008.

It is important to note that a similar effect can be observed among U.S. states (Wilkinson & Pickett, 2008) Again, absolute income does not play an important role. By contrast, the more unequal the state, the higher the rates of obesity, homicide, and teen pregnancy.

From an evolutionary and psychological perspective, the link between inequality and health and social problems is straightforward. Indeed, for humans as well as for most nonhuman primates, social status is crucial for survival. Humans have thus evolved specific mechanisms to deal with the issue of status. The trade-off here is the same as between slow and fast strategies. Individuals choose between a slow strategy, with long-term investments and low-risk choices, and a fast strategy, with short-term investments and high-risk choices (Daly & Wilson, 2001). When status is low, individuals face the risk of being eliminated from the race (not having enough resources for their children, not finding a mate, etc.). In this situation, it is better to switch to a risky strategy.

In real life, this translates into specific evolved behaviors. For males, it often means choosing violence to protect one's status and gain respect from others. For females, it means reproducing earlier and having more children (Daly & Wilson, 2001; Nettle, 2010a, 2010b). In line with this evolutionary logic, epidemiological studies have shown that violence occurs mostly among young males from lower SES, those in the greatest need of status and respect, and that violence is strongly related to inequality (Daly & Wilson, 2001). Homicide rates, for instance, are higher in the most unequal US states, in the most unequal Canadian provinces as well as in the most unequal OECD countries. Similarly, teen pregnancy strongly correlates with inequality both among U.S. states and OECD countries.

These correlations do not necessarily make sense from a standard economic model. Indeed, from a purely rational standpoint, it would seem sensible for someone with a low status in a modern society to work hard, invest in education, and postpone reproduction. It is only from an evolutionary perspective that these effects make sense. In environments of evolutionary adaptedness, where violence was higher and education less important, violence and teen pregnancy were indeed successful strategies for low-status individuals. They increased their chances of dying young or having no surviving children, but on average, they also increased their chances of climbing the social ladder.

Evolutionary theory also explains other effects of inequality, such as obesity. Although it is natural to us to find eating, and especially eating highly caloric food such as ice cream or pizza, comforting, this behavior requires an explanation. Why is it that stress makes us eat more? Again, the response lies in the particular environment in which our tastes evolved. As discussed above, for most of human history, resources were relatively scarce. Since stress signals that things are not going well, the organism makes food a higher priority, because in the past, when things went badly, it usually meant that food was going to become even scarcer (Nesse & Young, 2000). Our preferences change with stress, but so does our physiology. For instance, it has been shown that stress makes the organism more likely to transform calories into abdominal fat, a good indication that the body is preparing itself for harder times.

In line with this idea, rates of obesity in developed countries are highly correlated with inequality (Wilkinson & Pickett, 2008). In developed countries, where food and calories are abundant and cheap, eating large amounts to stockpile calories no longer makes sense. Yet, because it made sense in the evolutionary past, people still eat to cope with stress. As a result, countries where stress is higher because of high inequality tend to have a higher rate of obesity as well.

Eating fattier foods and stocking calories in the abdomen is part of a more general stress system regulated by hormones like cortisol, which aim at elevating the level of resources available to the organism (like the fear system) at the cost of its less immediate needs. For instance, the activation of the immune defense system decreases, which explains why stressed people are more likely to get sick. Thus, in the short term, stress can render the organism more efficient or more alert or give it more endurance, because it makes more resources available, but in the long term, stress is highly detrimental to the organism, which explains why inequality and stress are associated to myriad health problems, such as atherosclerosis and cardiovascular diseases (Nesse & Young, 2000).

To sum up, the evolutionary and psychological approach allows us to understand why inequality is so harmful to humans. Because humans are a social species, they care a great deal about status, and being in an unequal society makes them both less happy and more prone to develop problematic behaviors. Again, this result cannot be derived from a traditional economic perspective, which makes no assumptions about people's preferences, and in particular their preference for a high social status. This result is fundamental for public policy. The main argument typically presented in favor of equality is based on considerations of social justice. The evolutionary and psychological approach suggests that there is another, more neutral argument in favor of equality, which is that most people, rich and poor, would be better off in a more equal and less stressful society.

The High Cost of GDP-Centered Policies

Social support is central for humans, and just as competition is stressful, lack of support is painful. As recently demonstrated by brain imaging (Eisenberger, Lieberman, & Williams, 2003), social exclusion activates the same neural network as physical pain. This result makes sense from an evolutionary point of view. Indeed, just as physical pain signals the presence of physical threats to the organism, so does social pain signal the existence of social threats to the organism. Being alone is very bad news for most animals because it increases the risk of getting caught by a predator and decreases the chance of finding food, but it is particularly bad for humans since we cannot survive without social cooperation and support.

In line with this idea, stress has been found to increase greatly when social support decreases (for a review, see Diener & Seligman, 2004; Layard, 2006). Men and women with more friends were found to have lower levels of mental distress than those with fewer friends. The highest rates of mental problems are found among unmarried people, single parents, and people living alone. Individuals with close social bonds suffer if they are separated for long periods of time. For example, the wives of men who work on submarines often experience increased physical illness and depression during their spouses' absences. Here, stress is a very clear indication that human psychology treats lack of social support as a threat for the survival of the individual. This, as we have seen, ultimately increases the occurrence of physical and mental disease.

These empirical results are of great importance for public policy. Indeed, they highlight that friends and family are crucial for human well-being. People cannot be happy if they lack social support. In the past 20 years, a large amount of data have shown that, indeed, very happy people are, on average, people who have more close friends and stronger family and romantic relationships (from Diener & Seligman, 2002).

Similarly, people's social relationships have an equal if not greater impact on their well-being than their economic situation. For instance, while a one-third drop in income reduces happiness by 2 points, being widowed, divorced, or separated reduces happiness by 4, 5, and 8 points, respectively (Layard, 2006).

From this perspective, decreasing the quality or quantity of social relationships in exchange for higher income levels may not be good policy. People may get better-paid jobs and be able to afford more goods and services, but this may not compensate the adverse effects of losing contact with their family and friends. Of course, this is a trade-off, but policy makers should be aware of the critical importance of social relationships. As Diener and Seligman note, for instance, “the military and corporations should relocate employees and their families only when it is absolutely essential to do so, or when an employee requests it. Automatic moves every few years leave individuals without strong community ties, and with fewer close friends in times of crisis” (Diener & Seligman, 2004, p. 20). More generally, the potential effects of forcing people to move around the country and the world for the sake of job opportunities should be considered from this perspective whenever possible. People might be better off earning much less money near their family than being expatriates, and hence stranded at a great distance from their sustaining social network.

Social support is not the only human preference that is sacrificed by exclusively GDP-centered policies. Psychological studies have also shown that security is a very important component of well-being (for a review, see Layard, 2006). Living in an unpredictable environment, not knowing whether one will be able to keep one's job, for instance, is very stressful. From a psychological perspective, it might be better to have a job that pays less but is more secure than the contrary. In the same way, autonomy is a very important component of well-being, because it is very stressful for individuals to feel that they have no control over their lives. Working in a small company or a shop might be much better for an individual's well-being, even if it is less well paid, than working in a big company where individuals have less responsibility for their success and less control over their job.

Conclusion

The standard economic approach to human development assumes that most problems result from institutional failures. This is sometimes the case. But many other problems result from that fact that human behavior is often at odds with the goals of development policies: People fail to save for their retirement, they keep eating in an unhealthy way despite medical campaigns, they do not trust each other and refuse to cooperate, and so on. This is why people sometimes need a nudge from public policy.

But when do people need a nudge? In standard behavioral approaches, people are often said to need a nudge when the problem they face is complex, when it offers poor feedback, or when the costs must be paid now but the benefits will only come later (Thaler & Sunstein, 2008). But from a psychological point of view, this view doesn't stand up. Walking on two legs or learning thousands of words in the first 2 years of life is pretty complex, and the chief benefits are often quite far off. Yet, humans do it easily and effortlessly. Deciding which foods are toxic for the fetus is quite impossible, because individuals do not have the means to establish the causal link between one food and its effects—and yet women have very efficient and well-informed intuitions about which foods they should eat when pregnant. Finally, raising children costs a huge amount of resources, and the full benefit can only be enjoyed years later. Humans have no problem, however, when it comes to sacrificing their leisure time or their energy to take care of their offspring.

So when do people really need a nudge? The response that psychology offers is that they need to be nudged when their interests are not aligned their evolved psychology: when there is a gap between the ancestral environment and their current environment. These are the kinds of situations where people need public policies. And what is a good nudge? A good nudge is one that takes human psychology as a constraint, acknowledges its limits, and does not entertain grand expectations about human nature. But it is also a nudge that takes advantage of how human psychology works and uses its mechanisms as levers to increase the impact of public policies.

Notes

1. Note that adaptations are selected because they solve adaptive problems, on average, better than competing designs extant at the time. There are lots of cases in which properly functioning adaptations fail, even if situations closely match those in which they evolved.

2. Another possibility was for people to rely on kin, friends, and coalition to resolve conflict and deter defection.

References

1. Aktipis, C. A. (2004). Know when to walk away: Contingent movement and the evolution of cooperation. Journal of Theoretical Biology, 231(2), 249–260.
2. Alesina, A., & Glaeser, E. (2004). Fighting poverty in the US and Europe: A world of difference. Oxford, England: Oxford University Press.
3. Algan, Y., & Cahuc, P. (2006, January). Civic attitudes and the design of labor market institutions: Which countries can implement the Danish flexicurity model? IZA Discussion Paper No. 1928.
4. Bateson, M., Nettle, D., & Roberts, G. (2006). Cues of being watched enhance cooperation in a real-world setting. Biology Letters, 2(3), 412–414.
5. Baumard, N. (2010). Has punishment played a role in the evolution of cooperation? A critical review. Mind and Society, 9, 171–192.
6. Baumard, N., André, J.-B., & Sperber, D. (2013). A mutualistic approach to morality: The evolution of fairness by partner-choice. Behavioral and Brain Sciences, 36(1), 59–78.
7. Behavioural Insight Team. (2012). Applying behavioural insights to reduce fraud, error and debt. London, England: Cabinet Office.
8. Bettinger, E. P., Long, B. T., Oreopoulos, P., & Sanbonmatsu, L. (2012). The role of application assistance and information in college decisions: Results from the H&R Block FAFSA Experiment. The Quarterly Journal of Economics, 127(3), 1205–1242.
9. Bjørnskov, C., & Svendsen, G. T. (2012). Does social trust determine the size of the welfare state? Evidence using historical identification. Public Choice, 1–18.
10. Burnham, T., & Phelan, J. (2012). Mean genes: From sex to money to food: Taming our primal instincts. New York, NY: Basic Books.
11. Chetty, R., Friedman, J. N., Leth-Petersen, S., Nielsen, T. H., & Olsen, T. (2013, March). Subsidies vs. nudges: Which policies increase saving the most? Issue Brief 13–3. Boston, MA: Center for Retirement Research at Boston College.
12. Chisholm, J. S., Ellison, P. T., Evans, J., Lee, P. C., Lieberman, L. S., Pavlik, Z., Worthman, C. M. (1993). Death, hope, and sex: Life-history theory and the development of reproductive strategies [and comments and reply]. Current Anthropology, 34(1), 1–24.
13. Cialdini, R. B. (1993). Influence: The psychology of persuasion. New York, NY: Morrow.
14. Cosmides, L., & Tooby, J. (1997). Evolutionary psychology: A primer. Santa Barbara: Center for Evolutionary Psychology, University of California. Retrieved from http://www.cep.ucsb.edu/primer.html
15. Cosmides, L., & Tooby, J. (2013). Evolutionary psychology: New perspectives on cognition and motivation. Annual Review of Psychology, 64, 201–229.
16. Daly, M., & Wilson, M. (2001). Risk-taking, intrasexual competition, and homicide. In J. A. French, A. C. Kamil, & D. W. Leger (Eds.), Nebraska symposium on motivation: Vol. 47. Evolutionary psychology and motivation (pp. 1–36). Lincoln: University of Nebraska Press.
17. Datta, S., & Mullainathan, S. (2012). Behavioral design: A new approach to development policy. CDG Policy Paper No. 16, Center for Global Development, Washington, DC.
18. Diamond, J. (2012). The world until yesterday: What can we learn from traditional societies? New York, NY: Penguin.
19. Diener, E., & Seligman, M. E. P. (2002). Very happy people. Psychological Science, 13(1), 81.
20. Diener, E., & Seligman, M. E. P. (2004). Beyond money. Psychological Science in the Public Interest, 5(1), 1–31.
21. Eisenberger, N. I., Lieberman, M. D., & Williams, K. D. (2003). Does rejection hurt? An fMRI study of social exclusion. Science, 302(5643), 290–292.
22. Ellis, B. J., Figueredo, A. J., Brumbach, B. H., & Schlomer, G. L. (2009). Fundamental dimensions of environmental risk. Human Nature, 20(2), 204–268.
23. Ernest-Jones, M., Nettle, D., & Bateson, M. (2011). Effects of eye images on everyday cooperative behavior: A field experiment. Evolution and Human Behavior, 32(3), 172–178.
24. Frank, R. H. (1985). Choosing the right pond: Human behavior and the quest for status. New York, NY: Oxford University Press.
25. Frank, R. H. (2007). Falling behind: How rising inequality harms the middle class (Vol. 4). Berkeley: University of California Press.
26. Fukuyama, F. (1995). Trust: The social virtues and the creation of prosperity. New York, NY: Free Press.
27. Garner, R. (2005). Post-It® note persuasion: A sticky influence. Journal of Consumer Psychology, 15(3), 230–237.
28. Goldstein, N. J., Cialdini, R. B., & Griskevicius, V. (2008). A room with a viewpoint: Using social norms to motivate environmental conservation in hotels. Journal of Consumer Research, 35(3), 472–482.
29. Griskevicius, V., Ackerman, J. M., Cantú, S. M., Delton, A. W., Robertson, T. E., Simpson, J. A., & Tybur, J. M. (2013). When the economy falters, do people spend or save? Responses to resource scarcity depend on childhood environments. Psychological Science, 24(2), 197–205.
30. Haley, K., & Fessler, D. (2005). Nobody's watching? Subtle cues affect generosity in an anonymous economic game. Evolution and Human Behavior, 26(3), 245–256.
31. Hoebel, E. A. (1954). The law of primitive man: A study in comparative legal dynamics. Cambridge, MA: Harvard University Press.
32. Kaplan, H., & Gurven, M. (2005). The natural history of human food sharing and cooperation: A review and a new multi-individual approach to the negotiation of norms. In H. Gintis (Ed.), Moral sentiments and material interests: The foundations of cooperation in economic life (Vol. 6, pp. 75–113). Cambridge, MA: MIT Press.
33. Kaplan, H. S., Hooper, P. L., & Gurven, M. (2009). The evolutionary and ecological roots of human social organization. Philosophical Transactions of the Royal Society B: Biological Sciences, 364(1533), 3289–3299. doi:10.1098/rstb.2009.0115
34. Layard, R. (2006). Happiness: Lessons from a new science. New York, NY: Penguin.
35. Nesse, R. M., & Young, E. A. (2000). Evolutionary origins and functions of the stress response. Encyclopedia of Stress, 2, 79–84.
36. Nettle, D. (2010a). Dying young and living fast: Variation in life history across English neighborhoods. Behavioral Ecology, 21(2), 387–395.
37. Nettle, D. (2010b). Social class through the evolutionary lens—Daniel Nettle takes a look. Psychologist, 22(11), 934.
38. Nolan, J. M., Schultz, P. W., Cialdini, R. B., Goldstein, N. J., & Griskevicius, V. (2008). Normative social influence is underdetected. Personality and Social Psychology Bulletin, 34(7), 913–923.
39. Pinker, S. (1997). How the mind works. New York, NY: Norton.
40. Putnam, R. D. (2000). Bowling alone: The collapse and revival of American community. New York, NY: Simon & Schuster.
41. Roberts, G. (1998). Competitive altruism: From reciprocity to the handicap principle. Proceedings of the Royal Society B: Biological Sciences, 265, 427–431.
42. Roff, D. A. (2002). Life history evolution (Vol. 7). Sunderland, MA: Sinauer.
43. Solnick, S. J., & Hemenway, D. (1998). Is more always better? A survey on positional concerns. Journal of Economic Behavior & Organization, 37(3), 373–383.
44. Stearns, S. C. (1992). The evolution of life histories. New York, NY: Oxford University Press.
45. Thaler, R. H., & Sunstein, C. R. (2008). Nudge: Improving decisions about health, wealth, and happiness. New Haven, CT: Yale University Press.
46. Trivers, R. (1971). Evolution of reciprocal altruism. Quarterly Review of Biology, 46, 35–57.
47. Uslaner, E. M. (2002). The moral foundations of trust. Cambridge, England: Cambridge University Press.
48. Wilkinson, R., & Pickett, K. (2008). The spirit level. New York, NY: Allen Lane/Penguin Press.
49. Willinger, M., Keser, C., Lohmann, C., & Usunier, J. (2003). A comparison of trust and reciprocity between France and Germany: Experimental investigation based on the investment game. Journal of Economic Psychology, 24(4), 447–466.