Network reciprocity turns cheap talk into a force for cooperation

TL;DR

This paper presents a game-theoretic model showing that non-binding communication can promote cooperation in structured populations through cyclic dominance, explaining its evolutionary role despite being ineffective in well-mixed populations.

Contribution

It introduces a novel evolutionary model demonstrating how network reciprocity enables non-binding communication to foster cooperation in structured populations.

Findings

Non-binding communication alone cannot sustain cooperation in well-mixed populations.

Structured populations support cooperation through conditional strategies and cyclic dominance.

Conditional cooperators act as catalysts, protecting unconditional cooperators.

Abstract

Non-binding communication is common in daily life and crucial for fostering cooperation, even though it has no direct payoff consequences. However, despite robust empirical evidence, its evolutionary basis remains poorly understood. Here, we develop a game-theoretic model in which individuals can signal an intention to cooperate before playing a Donation game. Strategies differ in how they respond to these signals, ranging from unconditional to conditional types, with the latter incurring a cognitive cost for deliberation. Through evolutionary analysis, we show that non-binding communication alone cannot sustain cooperation in well-mixed, anonymous populations, consistent with empirical observations. In contrast, structured populations support the emergence of cooperation, with conditional cooperators acting as catalysts that protect unconditional cooperators through context-dependent patterns of cyclic dominance. These findings offer an evolutionary explanation for how non-binding communication promotes cooperation and provide a modelling framework for exploring its effects in diverse social settings.