Critical behavior in an evolutionary Ultimatum Game

TL;DR

This paper investigates how social network topology influences altruistic behavior in an evolutionary Ultimatum Game, revealing that social structure critically determines the distribution of offers and acceptance levels among individuals.

Contribution

It introduces an evolutionary model analyzing the impact of social network topology on altruism in the Ultimatum Game, highlighting the emergence of critical states and different offer distributions.

Findings

Population self-organizes in a critical state with altruism depending on network topology.

Heterogeneous networks favor intermediate offers, unlike homogeneous networks.

Individuals offering large or accepting large shares tend to be removed from the population.

Abstract

Experimental studies have shown the ubiquity of altruistic behavior in human societies. The social structure is a fundamental ingredient to understand the degree of altruism displayed by the members of a society, in contrast to individual-based features, like for example age or gender, which have been shown not to be relevant to determine the level of altruistic behavior. We explore an evolutionary model aiming to delve how altruistic behavior is affected by social structure. We investigate the dynamics of interacting individuals playing the Ultimatum Game with their neighbors given by a social network of interaction. We show that a population self-organizes in a critical state where the degree of altruism depends on the topology characterizing the social structure. In general, individuals offering large shares but in turn accepting large shares, are removed from the population. In heterogeneous social networks, individuals offering intermediate shares are strongly selected in contrast to random homogeneous networks where a broad range of offers, below a critical one, is similarly present in the population.