The Missing Piece: Why AI Models Hallucinate Answers When They Should Abstain

Automated excerpt

MISSING PIECE tests whether AI models can recognize when a multi-step reasoning problem is unanswerable and properly abstain by returning INSUFFICIENT, rather than hallucinating an unsupported answer. I designed 60 base problem templates across 6 core reasoning domains, generating 120 total evaluation instances (exactly 60 intact and 60 modified). Missing Quantity (20 Pairs / 40 Items): A required numerical quantity is omitted.

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