Evolution of prosocial behavior in multilayer populations

Abstract

Human societies include many types of social relationships. Friends, family, business colleagues, online contacts, and religious groups, for example, can all contribute to an individual's social life. Individuals may behave differently in different domains, but their success in one domain may nonetheless engender success in another. The complexity caused by distinct, but coupled, arenas of social interaction may be a key driver of prosocial or selfish behavior in societies. Here, we study this problem using multilayer networks to model a population with multiple domains of social interactions. An individual can appear in multiple different layers, each with separate behaviors and environments. We provide mathematical results on the resulting behavioral dynamics, for any multilayer structure. Across a diverse space of structures, we find that coupling between layers tends to promote prosocial behavior. In fact, even if prosociality is disfavored in each layer alone, multilayer coupling can promote its proliferation in all layers simultaneously. We apply these techniques to six real-world multilayer social networks, ranging from the networks of socio-emotional and professional relationships in a Zambian community, to the networks of online and offline relationships within an academic University. Our results suggest that coupling between distinct domains of social interaction is critical for the spread of prosociality in human societies.

Evolution of cooperation with asymmetric social interactions

“…Yet we have found that, even for such networks, conversion of some bidirectional edges to unidirectional can rescue cooperation. An important implication is that asymmetric interactions provide an alternative method of modifying population structure to promote cooperation—besides severing old ties and building new ones, as has been explored in the bidirected setting ( 16 , 20 , 59 ) ( SI Appendix , Fig. S9 ).…”

“…The literature has revealed several key insights into this enigma ( 4 ). Population structure is perhaps the most widely discussed mechanism that can promote cooperation ( 5 , 6 ), and it has been studied by computer simulation ( 7 – 9 ), mathematical analysis ( 10 – 21 ), and experiments with human subjects ( 22 ). In structured populations individuals interact only with their neighbors—through either physical or social ties—and behaviors also spread locally.…”

“…Population structure has the potential to favor the evolution of cooperative behaviors that would otherwise be disfavored in well-mixed populations ( 5 – 7 , 11 , 16 , 17 ). In network-structured populations, for example, nodes represent individuals and edges typically represent social interactions between connected individuals ( 9 – 12 , 14 – 19 ); in set-structured populations, each individual is located in one or more social circles ( 23 ); and in multilayer-structured populations, social interactions occur in multiple different domains, such as online and offline interactions, and payoffs to an individual are summed across domains ( 20 , 24 ).…”

“…Despite different approaches to describing population structure, nearly all research on this topic has assumed that social interactions and behavioral spread are bidirectional ( 7 – 20 , 22 ). That is, if Alice provides a benefit to Bob when behaving altruistically, Bob is presumed to provide a benefit to Alice when behaving altruistically; moreover, if Alice has a chance to imitate Bob’s behavior, then so too can Bob imitate Alice’s behavior.…”

Evolution of cooperation with asymmetric social interactions

“…The literature has revealed several key insights into this enigma [4]. Population structure is perhaps the most widely discussed mechanism that can promote cooperation [5,6], and it has been studied by computer simulation [7][8][9], mathematical analysis [1,2,10,[12][13][14][15][16][17][18][19][20], and experiments with human subjects [22]. In structured populations individuals interact only with their neighbors -through either physical or social ties -and behaviors also spread locally.…”