[Summary] Add metrics for feature attribution evaluation

[gsarti]

🚀 Feature Request

The following is a non-exhaustive list of attention-based feature attribution methods that could be added to the library:

Method name	Source	Code implementation	Status
Sensitivity	Yeh et al. '19	pytorch/captum
Infidelity	Yeh et al. '19	pytorch/captum
Log Odds	Shrikumar et al. '17	INK-USC/DIG
Sufficiency	De Young et al. '20	INK-USC/DIG
Comprehensiveness	De Young et al. '20	INK-USC/DIG
Human Agreement	Atanasova et al. '20	copenlu/xai-benchmark
Confidence Indication	Atanasova et al. '20	copenlu/xai-benchmark
Cross-Model Rationale Consistency	Atanasova et al. '20	copenlu/xai-benchmark
Cross-Example Rationale Consistency (Dataset Consistency)	Atanasova et al. '20	copenlu/xai-benchmark
Sensitivity	Yin et al. '22	Iuclanlp/NLP-Interpretation-Faithfulness
Stability	Yin et al. '22	Iuclanlp/NLP-Interpretation-Faithfulness

Notes:

1. The Log Odds metric is just the negative logarithm of the Comprehensiveness metric. The application of - log can be controlled by a parameter do_log_odds: bool = False in the same function. The reciprocal can be obtained for the Sufficiency metric.

2. All metrics that control masking/dropping a portion of the inputs via a top_k parameter can benefit from a recursive application to ensure the masking of most salient tokens at all times, as described in Madsen et al. '21. This could be captured by a parameter recursive_steps: Optional[int] = None. If specified, a masking of size top_k // recursive_steps + int(top_k % recursive_steps > 0) is performed for recursive_steps times, with the last step having size equal to top_k % recursive_steps if top_k % recursive_steps > 0.

3. The Sensitivity and Infidelity methods add noise to input embeddings, which could produce unrealistic input embeddings for the model (see discussion in Sanyal et al. '21). Both sensitivity and infidelity can include a parameter discretize: bool = False that when turned on replaces the top-k inputs with their nearest neighbors in the vocabulary embedding space instead of their noised versions. Using Stability is more principled in this context since fluency is preserved by the two step procedure presented by Alzantot et al. '18, which includes a language modeling component. An additional parameter sample_topk_neighbors: int = 1 can be used to control the nearest neighbors' pool size used for replacement.

4. Sensitivity by Yin et al. '22 is an adaptation to the NLP domain of Sensitivity-n by Yeh et al. '19. An important difference is that the norm of the noise vector causing the prediction to flip is used as a metric in Yin et al. '22, while the original Sensitivity in Captum uses the difference between original and noised prediction scores. The first should be prioritized for implementation.

5. Cross-Lingual Faithfulness by Zaman and Belinkov '22 (code) is a special case of the Dataset Consistency metric by Atanasova et al. 2020 in which the pair is constituted by an example and its translated variant.

Overviews

A Comparative Study of Faithfulness Metrics for Model Interpretability Methods, Chan et al. '22