arXiv Computation and Language By Chengguang Gan, Hanjun Wei, Yunhao Liang, Qinghao Zhang, Shiwen Ni, Zhixi Cai

How Output Format Confounds Data Quality and Capability in Instruction Tuning

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The paper investigates how the output format of instruction‑tuned models confounds assessments of data quality and model capability. By analyzing gradient signatures across multiple tasks, interfaces, and model families, the authors demonstrate that the interface can mask or exaggerate performance signals, with certain skills appearing only under specific output formats. They show that the interface‑varying residual is not noise but captures task‑specific information, and that correcting a single generation budget can flip the measured effect of fine‑tuning on a benchmark. "whyItMatters":"The study highlights that current evaluation practices may misrepresent a model’s true capabilities because they rely on the output interface rather than the underlying content, potentially leading to misleading conclusions about data quality and model performance."

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arXiv Computation and Language
Aug 27

Synthesizing Instruction-Tuning Datasets with Contrastive Decoding

The paper introduces CoDIT, a contrastive decoding technique that separates instruction-following behavior from pre-trained world knowledge in large language models. By generating responses that emphasize post-training instruction capabilities while suppressing shared pre-trained knowledge, CoDIT creates instruction-tuning datasets that lead to consistently better model performance than directly generated responses or existing public datasets. The authors also provide theoretical and empirical evidence that CoDIT effectively distills instruction-tuning knowledge from model parameters into text, facilitating cross-architecture transfer.

By Tatsuya Ichinose, Youmi Ma, Masanari Oi, Ryuto Koike, Naoaki Okazaki