Groups and scores: the decline of cooperation

Evolution of cooperation with joint liability

'Personal responsibility', one of the basic principles of social governance, requires one to be accountable for what one does. However, personal responsibility is far from the only norm ruling human interactions, especially in social and economic activities. In many collective communities such as among enterprise colleagues and family members, one's personal interests are often bound to others'-once one member breaks the rule, a group of people have to bear the punishment or sanction. Such a mechanism is termed 'joint liability'. Although many real-world cases have evidenced that joint liability can help to maintain collective collaboration, a deep and systematic theoretical analysis on how and when it promotes cooperation remains lacking. Here, we use evolutionary game theory to model an interacting system with joint liability, where one's losing credit could deteriorate the reputation of the whole group. We provide the analytical condition to predict when cooperation evolves and analytically prove that in the presence of punishment, being jointly liable greatly promotes cooperation. Our work stresses that joint liability is of great significance in promoting current economic prosperity.

Networks of reliable reputations and cooperation: a review

Reputation has been shown to provide an informal solution to the problem of cooperation in human societies. After reviewing models that connect reputations and cooperation, we address how reputation results from information exchange embedded in a social network that changes endogenously itself. Theoretical studies highlight that network topologies have different effects on the extent of cooperation, since they can foster or hinder the flow of reputational information. Subsequently, we review models and empirical studies that intend to grasp the coevolution of reputations, cooperation and social networks. We identify open questions in the literature concerning how networks affect the accuracy of reputations, the honesty of shared information and the spread of reputational information. Certain network topologies may facilitate biased beliefs and intergroup competition or in-group identity formation that could lead to high cooperation within but conflicts between different subgroups of a network. Our review covers theoretical, experimental and field studies across various disciplines that target these questions and could explain how the dynamics of interactions and reputations help or prevent the establishment and sustainability of cooperation in small- and large-scale societies.

This article is part of the theme issue ‘The language of cooperation: reputation and honest signalling’.

Cooperation through Image Scoring: A Replication

“Image scoring” is a type of social evaluation, originally used in agent-based models, where the reputation of another is numerically assessed. This phenomenon has been studied in both theoretical models and real-life psychology experiments (using human participants). The latter are aimed to create conditions in the laboratory where image scoring can be elicited. One influential paper is that of Wedekind and Milinski (2000), WM. Our paper is a replication of that study, deliberately employing very similar methodology to the original. Accordingly, we had six groups of ten participants play an economic game. In each round, each player was randomly paired with another player whose identity was unknown. The participant was given a binary choice of either (1) donating money to that person, or (2) not donating money. In each round, the player was passively exposed to information about the past generosity of the other player. In our study, we successfully replicated the central result of WM. Participants in our replication gave significantly more money to partners with higher image scores (more generous reputations) than those with lower image scores (less generous reputations). This paper also provides a critical review of the methodology of WM and the study of image scoring.

Aggression, Conflict, and the Formation of Intimidating Group Reputation

From inmates in prison gangs to soldiers in elite units, the intimidating reputation of groups often precedes its members. While individual reputation is known to affect people’s aggressiveness, whether one’s group reputation can similarly influence behavior in conflict situations is yet to be established. Using an economic game experiment, we isolate the effect of group reputation on aggression and conflict from that of individual reputation. We find that group reputation can increase the willingness to inflict costs on others but only when individuals are able to punish their fellow members. Even if internal discipline can sustain their shared reputation, more intimidating groups provide fewer benefits to their members in the short run. Using an agent-based simulation, we show that this might not be the case in the long run. Our findings yield insights into the effects of group reputation on aggression, conflict, and possible consequences for group survival.

When Two Become One: How Group Mergers Affect Solidarity

Solidarity in teamwork situations is important for the success and longevity of teams. This paper studies how helping group members is affected when groups are randomly merged and increase in size. Group mergers put social norms that are prevailing in previously small groups to the test as new team members may not share the same norms and values. I present results from an experiment in which subjects interact in groups and face the decision to help a group member who is in need of help due to an exogenous shock. Subjects interact in small groups in the first part of the experiment and groups are randomly merged to form big groups in the second part of the experiment. Helping rates are higher in merged groups compared with big groups that stay in the same constellation throughout the experiment. Moreover, in merged groups, high helping norms are more influential compared with low helping norms.