Task–Specificity Score: Measuring How Much Instructions Really Matter for Supervision

Pritam Kadasi, Abhishek Upperwal, Mayank Singh


Abstract
Instruction tuning is now the default way to train and adapt large language models, but many instruction–input–output pairs are only weakly specified: for a given input, the same output can remain plausible under several alternative instructions. This raises a simple question: does the instruction uniquely determine the target output? We propose the Task–Specificity Score (TSS) to quantify how much an instruction matters for predicting the target output by contrasting the true instruction against plausible alternatives for the same input. We further introduce TSS++, which uses hard alternatives and a small quality term to mitigate easy-negative effects. Across three instruction datasets (Alpaca, Dolly-15K, NI-20) and three open LLMs (Gemma, Llama, Qwen), our strongest evidence appears in the tightest budget regime, particularly at 5% retention. In this setting, TSS and TSS++ consistently outperform existing selection baselines across most model–dataset combinations. These results show that task specificity is a useful signal for low-budget instruction-data selection and complements existing filters such as perplexity and IFD.
Anthology ID:
2026.emnlp-main.1945
Volume:
Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Hung-Yi Lee, Sunipa Dev, Jessy Li, Desmond Elliott
Venue:
EMNLP
SIG:
SIGDAT
Publisher:
Association for Computational Linguistics
Note:
Pages:
44255–44267
Language:
URL:
https://aclanthology.org/2026.emnlp-main.1945/
DOI:
Bibkey:
Cite (ACL):
Pritam Kadasi, Abhishek Upperwal, and Mayank Singh. 2026. Task–Specificity Score: Measuring How Much Instructions Really Matter for Supervision. In Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing, pages 44255–44267, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Task–Specificity Score: Measuring How Much Instructions Really Matter for Supervision (Kadasi et al., EMNLP 2026)
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PDF:
https://aclanthology.org/2026.emnlp-main.1945.pdf