Paradoxical examples of social networks games with product choice

TL;DR

This paper investigates paradoxical phenomena in social network games where adding strategies can reduce overall payoffs, and it introduces a new construction to demonstrate all known paradox types.

Contribution

The paper resolves an open question by constructing examples of vulnerable networks for all four paradox types using a novel cascade method.

Findings

Constructed uniform examples for all four paradox types.

Proved existence of strongly vulnerable networks.

Introduced the cascade construction method.

Abstract

Paradox of choice occurs when permitting new strategies to some players yields lower payoffs for all players in the new equilibrium via a sequence of individually rational actions. We consider social network games. In these games the payoff of each player increases when other players choose the same strategy. The definition of games on social networks was introduced by K. Apt and S. Simon. In an article written jointly with E. Markakis, they considered four types of paradox of choice in such games and gave examples of three of them. The existence of paradoxical networks of the fourth type was proven only in a weakened form. The existence of so-called vulnerable networks in the strong sense remained an open question. In the present paper we solve this open question by introducing a construction, called a cascade, and use it to provide uniform examples for all four definitions of paradoxical networks.