@inproceedings{huang-etal-2026-beft,
title = "{BEFT}: Bias-Efficient Fine-Tuning of Language Models in Low-Data Regimes",
author = "Huang, Baichuan and
Balashankar, Ananth and
Aminifar, Amir",
editor = "Liakata, Maria and
Moreira, Viviane P. and
Zhang, Jiajun and
Jurgens, David",
booktitle = "Proceedings of the 64th Annual Meeting of the {A}ssociation for {C}omputational {L}inguistics (Volume 1: Long Papers)",
month = jul,
year = "2026",
address = "San Diego, California, United States",
publisher = "Association for Computational Linguistics",
url = "https://aclanthology.org/2026.acl-long.1799/",
pages = "38833--38851",
ISBN = "979-8-89176-390-6",
abstract = "Fine-tuning the bias terms of large language models (LLMs) has the potential to achieve unprecedented parameter efficiency while maintaining competitive performance, particularly in low-data regimes. However, the link between fine-tuning different bias terms (i.e., $\boldsymbol{b}_q$, $\boldsymbol{b}_k$, $\boldsymbol{b}_v$ in the query, key, or value projections) and downstream performance remains largely unclear to date. In this paper, we investigate the link between fine-tuning $\boldsymbol{b}_q$, $\boldsymbol{b}_k$, $\boldsymbol{b}_v$ with the performance of the downstream task. Our key finding is that *directly fine-tuning $\boldsymbol{b}_v$ generally leads to higher downstream performance in low-data regimes, in comparison to $\boldsymbol{b}_q$ and $\boldsymbol{b}_k$*. We extensively evaluate this unique property across a wide range of LLMs spanning encoder-only and decoder-only architectures up to 6.7B parameters (including bias-free LLMs). Our results provide strong evidence for the effectiveness of directly fine-tuning $\boldsymbol{b}_v$ across various downstream tasks. The implementation code is available at https://github.com/whubaichuan/BEFT."
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<abstract>Fine-tuning the bias terms of large language models (LLMs) has the potential to achieve unprecedented parameter efficiency while maintaining competitive performance, particularly in low-data regimes. However, the link between fine-tuning different bias terms (i.e., \boldsymbolb_q, \boldsymbolb_k, \boldsymbolb_v in the query, key, or value projections) and downstream performance remains largely unclear to date. In this paper, we investigate the link between fine-tuning \boldsymbolb_q, \boldsymbolb_k, \boldsymbolb_v with the performance of the downstream task. Our key finding is that *directly fine-tuning \boldsymbolb_v generally leads to higher downstream performance in low-data regimes, in comparison to \boldsymbolb_q and \boldsymbolb_k*. We extensively evaluate this unique property across a wide range of LLMs spanning encoder-only and decoder-only architectures up to 6.7B parameters (including bias-free LLMs). Our results provide strong evidence for the effectiveness of directly fine-tuning \boldsymbolb_v across various downstream tasks. The implementation code is available at https://github.com/whubaichuan/BEFT.</abstract>
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%0 Conference Proceedings
%T BEFT: Bias-Efficient Fine-Tuning of Language Models in Low-Data Regimes
%A Huang, Baichuan
%A Balashankar, Ananth
%A Aminifar, Amir
%Y Liakata, Maria
%Y Moreira, Viviane P.
%Y Zhang, Jiajun
%Y Jurgens, David
%S Proceedings of the 64th Annual Meeting of the Association for Computational Linguistics (Volume 1: Long Papers)
%D 2026
%8 July
%I Association for Computational Linguistics
%C San Diego, California, United States
%@ 979-8-89176-390-6
%F huang-etal-2026-beft
%X Fine-tuning the bias terms of large language models (LLMs) has the potential to achieve unprecedented parameter efficiency while maintaining competitive performance, particularly in low-data regimes. However, the link between fine-tuning different bias terms (i.e., \boldsymbolb_q, \boldsymbolb_k, \boldsymbolb_v in the query, key, or value projections) and downstream performance remains largely unclear to date. In this paper, we investigate the link between fine-tuning \boldsymbolb_q, \boldsymbolb_k, \boldsymbolb_v with the performance of the downstream task. Our key finding is that *directly fine-tuning \boldsymbolb_v generally leads to higher downstream performance in low-data regimes, in comparison to \boldsymbolb_q and \boldsymbolb_k*. We extensively evaluate this unique property across a wide range of LLMs spanning encoder-only and decoder-only architectures up to 6.7B parameters (including bias-free LLMs). Our results provide strong evidence for the effectiveness of directly fine-tuning \boldsymbolb_v across various downstream tasks. The implementation code is available at https://github.com/whubaichuan/BEFT.
%U https://aclanthology.org/2026.acl-long.1799/
%P 38833-38851
Markdown (Informal)
[BEFT: Bias-Efficient Fine-Tuning of Language Models in Low-Data Regimes](https://aclanthology.org/2026.acl-long.1799/) (Huang et al., ACL 2026)
ACL