知识蒸馏会削弱模型的去偏能力,研究提出改进方案。
Do Students Debias Like Teachers? On the Distillability of Bias Mitigation Methods
- 发现知识蒸馏会使教师模型的去偏能力难以传递给学生模型。
- 蒸馏后模型对不同偏见类型鲁棒性差异显著,整体鲁棒性可能不变。
- 提出数据增强、迭代蒸馏和权重初始化三类提升去偏可蒸馏性的方法。
知识蒸馏(KD)是模型压缩与知识迁移的有效方法,但其对模型在分布外数据上抵抗虚假相关性的鲁棒性影响尚未深入探索。本研究系统考察了知识蒸馏在自然语言推理(NLI)和图像分类任务中对教师模型去偏能力向学生模型迁移的影响。通过大量实验发现:(i) 整体而言,蒸馏会削弱模型的去偏能力;(ii) 训练去偏模型无法从注入教师知识中获益;(iii) 尽管模型整体鲁棒性可能保持稳定,但不同偏见类型间的鲁棒性变化显著;(iv) 精确识别出导致蒸馏后行为差异的内部注意力模式与神经回路。基于以上发现,提出三项有效改进策略:构建高质量增强数据、采用迭代知识蒸馏、使用教师模型权重初始化学生模型。据我们所知,这是首个在大规模上研究知识蒸馏对去偏影响及其内在机制的研究。研究成果为理解蒸馏机制及设计更优去偏方法提供了新视角。
原文摘要 · Abstract (English)
Knowledge distillation (KD) is an effective method for model compression and transferring knowledge between models. However, its effect on model's robustness against spurious correlations that degrade performance on out-of-distribution data remains underexplored. This study investigates the effect of knowledge distillation on the transferability of ``debiasing'' capabilities from teacher models to student models on natural language inference (NLI) and image classification tasks. Through extensive experiments, we illustrate several key findings: (i) overall the debiasing capability of a model is undermined post-KD; (ii) training a debiased model does not benefit from injecting teacher knowledge; (iii) although the overall robustness of a model may remain stable post-distillation, significant variations can occur across different types of biases; and (iv) we pin-point the internal attention pattern and circuit that causes the distinct behavior post-KD. Given the above findings, we propose three effective solutions to improve the distillability of debiasing methods: developing high quality data for augmentation, implementing iterative knowledge distillation, and initializing student models with weights obtained from teacher models. To the best of our knowledge, this is the first study on the effect of KD on debiasing and its interenal mechanism at scale. Our findings provide understandings on how KD works and how to design better debiasing methods.
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