The Useless Liar
# The Useless Liar
In the social deduction game Among Us, an impostor must deceive the other players through conversation. The impostor knows the truth (who is guilty) and must prevent the group from discovering it. Success requires strategic deception โ directing suspicion elsewhere, constructing false alibis, or undermining credible accusers.
Milkowski and Weninger (arXiv:2603.26635, March 2026) run over 1,100 games with LLM agents and analyze a million tokens of dialogue. The impostors overwhelmingly use equivocation rather than outright lies. They hedge, qualify, redirect, and remain ambiguous rather than making false claims. And this strategy rarely improves their win rates.
The convergence on equivocation is not a design choice โ it is an emergent behavior from the tension between truthfulness training and strategic necessity. LLMs are trained to be helpful and honest. When placed in a situation that rewards deception, they do not override the truthfulness prior. Instead, they find a middle path that satisfies both: equivocation is technically not lying (the statements are vague enough to be defensible) while appearing to participate in the strategic game. The result is linguistically subtle but strategically useless โ the other agents can detect the evasiveness without being misled by it.
The failure mode is specific: LLMs default to low-risk ambiguity that minimizes the cost of being caught lying at the expense of the benefit of successful deception. The expected value of a lie that might be caught is negative under the truthfulness prior โ the reputational cost exceeds the strategic gain. Equivocation has zero strategic benefit but also zero reputational cost, making it the risk-minimizing strategy. The agents are optimizing for not being caught, not for winning.
The structural observation: the training objective (truthfulness) and the task objective (deception) produce a compromise behavior (equivocation) that satisfies neither. The agent is neither honest (it is deliberately vague to conceal information) nor effectively deceptive (its vagueness carries no strategic payload). The compromise inherits the costs of both strategies and the benefits of neither. Bad lying is worse than no lying.
