IBM study: Rephrasing questions swings LLM benchmark scores by up to 74.7 points

rohanpaul_ai · x · 2026-08-20

A new IBM paper introduces BenchDrift, an auditing framework that systematically rephrases benchmark questions without changing answers, revealing that model scores can swing by an average of 74.7 percentage points across 8 models and 3 benchmarks. Stronger models are more affected, and even high-confidence answers are lost 18.5% of the time after rewording. The authors advise testing multiple phrasings or reporting score ranges when comparing models.

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