Interactional Fairness in LLM Multi-Agent Systems: An Evaluation Framework

TL;DR

This paper introduces a new framework for evaluating interactional fairness in LLM multi-agent systems, adapting organizational psychology tools to measure fairness as a behavioral property in agent interactions.

Contribution

It extends fairness evaluation to non-sentient agents and provides an empirical validation framework using controlled simulations and established fairness measurement tools.

Findings

Tone and explanation quality influence acceptance decisions.

Interactional fairness impacts agent behavior.

Context affects the influence of fairness types.

Abstract

As large language models (LLMs) are increasingly used in multi-agent systems, questions of fairness should extend beyond resource distribution and procedural design to include the fairness of how agents communicate. Drawing from organizational psychology, we introduce a novel framework for evaluating Interactional fairness encompassing Interpersonal fairness (IF) and Informational fairness (InfF) in LLM-based multi-agent systems (LLM-MAS). We extend the theoretical grounding of Interactional Fairness to non-sentient agents, reframing fairness as a socially interpretable signal rather than a subjective experience. We then adapt established tools from organizational justice research, including Colquitt's Organizational Justice Scale and the Critical Incident Technique, to measure fairness as a behavioral property of agent interaction. We validate our framework through a pilot study using controlled simulations of a resource negotiation task. We systematically manipulate tone, explanation quality, outcome inequality, and task framing (collaborative vs. competitive) to assess how IF influences agent behavior. Results show that tone and justification quality significantly affect acceptance decisions even when objective outcomes are held constant. In addition, the influence of IF vs. InfF varies with context. This work lays the foundation for fairness auditing and norm-sensitive alignment in LLM-MAS.