Journal article
Two Kinds of Missing: Underspecified Inputs Versus Unknown Answers, and Why One Abstention Policy Cannot Serve Both
A language model that declines to answer is scored the same way whether the reason is that the question has several readings and it picked the wrong one, or that the question has one reading and the model does not know the fact it names. AbstentionBench (Kirichenko et al., 2025) makes the…