Inequality and cooperation in social networks

Abstract

Social networks are fundamental to the broad scale cooperation observed in human populations. But by structuring the flow of benefits from cooperation, networks also create and sustain macro-level inequalities. Here we ask how two aspects of inequality shape the evolution of cooperation in dynamic social networks. Results from a crowdsourced experiment (N = 1080) show that inequality alters the distribution of cooperation within networks such that participants engage in more costly cooperation with their wealthier partners in order to maintain more valuable connections to them. Inequality also influences network dynamics, increasing the tendency for participants to seek wealthier partners, resulting in structural network change. These processes aggregate to alter network structures and produce greater system-level inequality. The findings thus shed critical light on how networks serve as both boon and barrier to macro-level human flourishing.

Figure 1

Illustration of our wealth productivity manipulation. As alters endowment increases, so does the amount ego receives from varying levels of alter’s cooperation (10, 30, and 50).

Figure 2

Average (A) cooperation and (B) inequality (Gini coefficient) by experimental condition through time. No Productivity, Equality indicates no wealth productivity and baseline endowment equality. Productivity, Inequality indicates wealth productivity and baseline endowment inequality.

Figure 3

Marginal cooperation illustrating the interaction between wealth productivity, baseline inequality and round.

Figure 4

Marginal means from Model 3 of Table 1 illustrating the interaction between wealth productivity, baseline (manipulated) inequality, and observed network-level inequality.

Figure 5

Marginal means from Model 4 of Table 1 illustrating the interaction between wealth productivity and average alter endowment.

Figure 6

Cumulative (A) tie updates and (B) network isolates by experimental condition through time.

Figure 7

Marginal change in number of partners illustrating the interaction between participant baseline wealth and wealth productivity.

Figure 8

Cox Proportional Hazard model survival probabilities at each network update by experimental condition. Participant endowments and cooperation (time-varying covariates) are set to their means.

Figure 9

Marginal Inequality depicting the interaction between round, initial baseline endowment inequality, and wealth productivity.