Attention is not Explanation
Written for the Research library (claude-opus-5-5) from the paper text. Original — aclanthology.org/N19-1357.pdf
Summary
Attention heatmaps are often shown as evidence of which input tokens drive a neural model's decision. Jain and Wallace test whether this interpretation holds. They study text classification, question answering and natural language inference, using mainly BiRNN (BiLSTM) encoders with additive or scaled dot-product attention. Convolutional and averaged-embedding encoders serve as points of comparison.
They ask two questions:
- Do attention weights agree with gradient-based and leave-one-out measures of token importance?
- Would different attention distributions actually change the prediction?
To answer the second, they randomly permute the learned weights and also search for adversarial distributions. These adversarial distributions differ as much as possible from the original while keeping the output nearly fixed.
With recurrent encoders, agreement with importance measures is weak and inconsistent. Very different attention patterns, whether shuffled or adversarially constructed, often leave predictions essentially unchanged.
The authors conclude that standard attention should not be presented as an explanation of model behaviour. They call for more principled, interpretability-oriented attention variants.
Key points
- Benchmarks:
- Classification: SST, IMDB, Twitter ADR, 20 Newsgroups (Hockey vs Baseball), AG News (Business vs World), and MIMIC ICD9 tasks (Diabetes; Chronic vs Acute Anemia).
- QA: CNN, bAbI tasks 1–3.
- NLI: SNLI.
- Correlation with gradients: Kendall τ between attention and gradient importance is modest for BiLSTM models (about 0.34–0.36 on SST). It is noticeably higher for the non-recurrent average encoder (about 0.60–0.61 on SST).
- Example review (Figure 1): For a negative movie review predicted at 0.01, an adversarial attention map over entirely different words gives the same output. Correlation with gradient importance is only τ_g = 0.29, and shuffling the weights shifts the output by a median of just 0.006.
- Limitations noted by the authors:
- Gradient-based measures are not treated as ground truth.
- Adversarial weights may be unlikely under the trained model.
- Only simple attention variants and non-seq2seq tasks were examined.
- Code: available at github.com/successar/AttentionExplanation.
Cited by
- Quantifying Attention Flow in Transformers
- Neural Legal Judgment Prediction in English
- Paragraph-level Rationale Extraction through Regularization: A case study on European Court of Human Rights Cases
- A Survey on Automated Fact-Checking
- Towards Faithfully Interpretable NLP Systems: How Should We Define and Evaluate Faithfulness?
- Attention is Not Only a Weight: Analyzing Transformers with Vector Norms
- Pre-trained Models for Natural Language Processing: A Survey
- Harnessing the linguistic signal to predict scalar inferences
- Is Attention Interpretable?
- AutoPrompt: Eliciting Knowledge from Language Models with Automatically Generated Prompts
- Masked Language Modeling and the Distributional Hypothesis: Order Word Matters Pre-training for Little
- Analyzing the Structure of Attention in a Transformer Language Model
- A Multiscale Visualization of Attention in the Transformer Model
- Attention is not not Explanation
- Explainability for Large Language Models: A Survey
- Representation Engineering: A Top-Down Approach to AI Transparency
Cite
@inproceedings{jain2019attention,
title = {{Attention is not Explanation}},
author = {Jain, Sarthak and Wallace, Byron C.},
booktitle = {Proceedings of the 2019 Conference of the North American Chapter of the Association for Computational Linguistics: Human Language Technologies, Volume 1 (Long and Short Papers)},
year = {2019},
doi = {10.18653/v1/n19-1357},
url = {https://doi.org/10.18653/v1/n19-1357}
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