The Vote-Left Equilibrium: A Deterministic Coordination Strategy for the Faithful in The Traitors

TL;DR

This paper introduces the Vote-Left protocol, a deterministic voting strategy in social deduction games that improves the Faithful's chances of winning by deterring Traitor collusion and ensuring predictable voting behavior.

Contribution

The Vote-Left protocol is a novel deterministic voting rule that forms a Perfect Bayesian Equilibrium and enhances the Faithful's success probability in the game.

Findings

Vote-Left aligns with random voting under full compliance.

It forms a Perfect Bayesian Equilibrium in certain game states.

Raises Faithful's winning probability by about three times over random voting with collusion.

Abstract

The Traitors is a social deduction game in which an informed minority of Traitors face an uninformed majority of Faithful, and the recurring question facing the Faithful is how to vote. Random voting is known to be optimal for the uninformed majority under simultaneous-signal protocols [Braverman, Etesami and Mossel, 2008], but when votes are cast individually, random votes are indistinguishable from strategic ones and the Faithful remain exposed to coordinated Traitor collusion. We introduce the Vote-Left protocol, a deterministic rule under which every player votes for the next surviving player in a fixed cyclic ordering. Under full compliance every surviving player receives exactly one vote, so the banishment distribution coincides with random voting; since prescribed votes are deterministic functions of public information, any deviation is immediately identifiable. Combined with a simple punishment rule, Vote-Left constitutes a Perfect Bayesian Equilibrium for every state with $n_t > 2m_t + 2$, a region that contains every televised configuration. We characterise the Traitors' best response in the late-game phase ($n_t \leq 2m_t + 2$): deviate via collusion once the Faithful no longer have enough votes to guarantee punishment. Across the configurations played on television, Vote-Left raises the Faithful's winning probability by a factor of approximately three over random voting under collusion.