用注意力引导蒸馏评估机器翻译解释方法,找出最有效的特征归因方式。
Evaluating Explainable AI Attribution Methods in Neural Machine Translation via Attention-Guided Knowledge Distillation
- 用教师模型的归因图作为信号,指导学生模型注意力机制。
- 注意力、值置零、层梯度×激活法在BLEU上提升最大,优于其他梯度法。
- 能更好复现归因图的模型,其解释信号对任务帮助更大,适合研究者参考。
神经网络输入特征归因的研究活跃,但序列到序列模型中可解释AI方法的系统化自动评估仍不充分。本文提出一种新方法,利用教师模型生成的归因图作为结构化辅助信号,指导学生模型学习。通过Inseq库提取源-目标序列对的归因分数,并以四种组合算子(加法、乘法、平均、替换)注入学生Transformer模型的注意力机制。在德英、法英、阿英三个语言对上,基于Marian-MT和mBART模型的注意力、值置零、层梯度×激活法在BLEU(及chrF)上显著优于基线;而Saliency、Integrated Gradients、DeepLIFT等梯度法提升较小且不稳定。结果表明不同归因方法捕捉不同信号,注意力衍生归因更契合源目标表示对齐。最后引入Attributor Transformer,可从源-目标对重建教师归因图,发现重建越准确,归因注入对下游任务越有用。代码开源。
原文摘要 · Abstract (English)
The study of the attribution of input features to the output of neural network models is an active area of research. While numerous Explainable AI (XAI) techniques have been proposed to interpret these models, the systematic and automated evaluation of these methods in sequence-to-sequence (seq2seq) models is less explored. This paper introduces a new approach for evaluating explainability methods in transformer-based seq2seq models. We use teacher-derived attribution maps as a structured side signal to guide a student model, and quantify the utility of different attribution methods through the student's ability to simulate targets. Using the Inseq library, we extract attribution scores over source-target sequence pairs and inject these scores into the attention mechanism of a student transformer model under four composition operators (addition, multiplication, averaging, and replacement). Across three language pairs (de-en, fr-en, ar-en) and attributions from Marian-MT and mBART models, Attention, Value Zeroing, and Layer Gradient $\times$ Activation consistently yield the largest gains in BLEU (and corresponding improvements in chrF) relative to baselines. In contrast, other gradient-based methods (Saliency, Integrated Gradients, DeepLIFT, Input $\times$ Gradient, GradientShap) lead to smaller and less consistent improvements. These results suggest that different attribution methods capture distinct signals and that attention-derived attributions better capture alignment between source and target representations in seq2seq models. Finally, we introduce an Attributor transformer that, given a source-target pair, learns to reconstruct the teacher's attribution map. Our findings demonstrate that the more accurately the Attributor can reproduce attribution maps, the more useful an injection of those maps is for the downstream task. The source code can be found on GitHub.
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