Zurück zur Hauptseite

The social dilemma of social distancing


Within only a few weeks, our lives have changed completely. Public life has been reduced to a minimum and non-essential business has been shut down. In order to prevent a further spread of COVID 19, we have been asked to physically isolate ourselves from our friends and even the closest family members, including our parents and grandparents. While people differ in the particular challenges they face – social isolation, no daycare for children, losing their income and their jobs – it seems safe to say that everyone has to make sacrifices.  


Social dilemmas. Evolutionary biologists and social scientists refer to such situations as social dilemmas. In a social dilemma, people need to cooperate for the good of a group, yet each individual may be tempted not to do their share. Social dilemmas pervade our social lives even in the absence of a pandemic. They affect companies who want to promote efficient teamwork just as they affect entire nations who need to collaborate to stop climate change. During the last weeks of crisis, however, the tensions that occur in a social dilemma have become particularly salient.   


A social dilemma as a game. To explore human behavior in social dilemmas, researchers have designed a simple experiment that captures some of these tensions. The experiment asks its participants, somewhat innocently called players, to engage in a so-called public good game. While the game can be played with any number of participants, we shall consider the game for a group of four. In the beginning of the game, each player receives some monetary endowment, say ten Euros each. Then each player independently decides how much of their endowment they wish to contribute to the public good. According to the rules of the game, total contributions are then doubled by the experimenter. The resulting sum is evenly divided among all players, including those who did not contribute. From a group perspective one can easily see that everyone should contribute their full endowment. In that case, everyone’s endowment is doubled and players receive twenty Euros each, instead of their initial ten. However, from an individual’s perspective, this does not lead to the highest payoff. If one player expects all others to contribute, he can reach a higher payoff by keeping all his endowment. In that case, his payoff will be twenty-five euros (10 Euros from his own endowment plus 15 Euros from the public good, as displayed in the Figure below). According to this logic, players must not contribute if they aim to maximize their private payoff. In terms of game theory, cooperation is a dominated strategy; a behavior that ought to disappear in the long run.



Figure: A public goods game involves four steps. In the first step, each individual is given some endowment. In the second step, individuals decide how much of their endowment they want to contribute to a joint public good. In this example, the three blue players give all their endowment whereas the remaining red player gives nothing. In the third step, all contributions to the public good are doubled. In the last step, all individuals receive an equal share from the public good.


Humans playing social dilemmas. But is this the way humans would play this game? The answer depends on the exact setup of the game and how the parameters have been chosen. Numerous controlled experiments suggest the following regularities.

  1. People are more likely to give if their contributions are more effective. In the above public good game this could be achieved, for example, by stipulating that total contributions are multiplied by three instead of two.
  2. People contribute more when they interact repeatedly. When participants encounter each other over multiple rounds, they can be held accountable in subsequent rounds. By not contributing today, players may motivate others to stop contributing, too. Especially in small groups of three or four, this shadow of the future can be sufficient to discipline people.
  3. Even in repeated interactions it becomes increasingly difficult to sustain cooperation when groups become large. As soon as the group size exceeds a critical threshold, contributions quickly tend to zero. Large groups create a diffusion of responsibility. Caring for the public good becomes someone else’s problem.


Mechanisms for cooperation. For a public good game that affects millions of people, these news may seem discouraging. Fortunately, however, there has been considerable research into mechanisms that can help sustaining cooperation. One such mechanism is population structure. We do not directly interact with all those millions of people who are threatened by the virus – we only interact with a much smaller number of friends, colleagues, and family members. Population structure does not only reduce the chance that the virus is transmitted from one person to the other. According to research on this topic, it also makes it more likely that people contribute to the public good because it reduces each individual’s effective group size.


Another way how human societies maintain cooperation is by punishing those who do not follow the rules. Current research distinguishes between two kinds of punishment, depending on who enforces the norms. Some norms are enforced by peer punishment. Here, group members take it onto themselves to discipline others, for example by drawing attention to somebody’s wrong behavior. Early experiments show that such peer punishment can be highly effective. Simply by allowing for sanctions, cooperation rates increase substantially and there is rarely a need to actually punish. However, subsequent research has shown that the success of peer punishment is sensitive on the existing cultural norms of a society. If sanctions are not administered responsibly, peer punishment can quickly give rise to counter-punishment and prolonged vendettas. It can also be misdirected and has in the current crisis led to hostility towards foreigners and non-locals. In addition, in countries like Germany, peer policing may have a negative connotation, because it is reminiscent of historical systems established to denounce political dissidents (“Blockwart” or “Abschnittsbevollmächtigter”).


Alternatively, punishment can be administered by dedicated central institutions, like the police and the executive branch of government more generally. Interestingly, maintaining such institutions is itself a public good that requires individual contributions in form of taxes. However, especially in crises like this one, central institutions prove their value. These institutions do not only help to enforce rules – they are also crucial in reaching a consensus on which rules people should obey in the first place. The worth of central institutions is reflected in the maxim of the US Internal Revenue Service – “Taxes is what we pay for a civilized society”.


While central institutions can help us to maintain public order, we must not overburden them. In these times, we all need to take on social responsibility, by contributing to the public good of sustaining our health care system. The easiest way to do so is to respect the implemented social distancing measures, and helping those in need. While doing so is costly, the public good game we currently face is certainly one we don’t want to lose.


Dr. Christian Hilbe und Prof. Dr. Arne Traulsen

(Scientists at the Max Planck Institute for Evolutionary Biology who specialize on mathematical Modelling)