LLM decision models favor extreme numeric options; debiasing drops benchmark score from 60 to 45

antoine_chaffin · x · 2026-10-29

An HF developer shares an eval bias: LLMs asked to generate distractors for numeric questions tend to place the answer at an extreme value and distractors in the middle, a bias that carries over to benchmarks. Debiasing his decision model on option length dropped its Habermas Machine score from 60 to 45 — below the "pick the longest" heuristic (50% vs 24% random). He accepts the lower score, arguing debiasing prevents collapse when options gain a few tokens.

Related event: Researchers Warn LLM Benchmarks Skewed by Option Bias, Debiasing Can Lower Scores(3 posts)→

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