LibraGrad: Balancing Gradient Flow for Universally Better Vision Transformer Attributions

TL;DR

LibraGrad is a post-hoc method that corrects gradient flow imbalances in Transformers to improve the faithfulness and quality of gradient-based attribution explanations across various architectures and datasets.

Contribution

It introduces LibraGrad, a theoretically grounded approach that prunes and scales backward paths to enhance gradient explanations without modifying the forward pass or adding overhead.

Findings

Universal improvement of gradient explanations across 8 architectures.

Outperforms existing white-box attribution methods on all metrics.

Effective even on attention-free architectures like MLP-Mixer.

Abstract

Why do gradient-based explanations struggle with Transformers, and how can we improve them? We identify gradient flow imbalances in Transformers that violate FullGrad-completeness, a critical property for attribution faithfulness that CNNs naturally possess. To address this issue, we introduce LibraGrad -- a theoretically grounded post-hoc approach that corrects gradient imbalances through pruning and scaling of backward paths, without changing the forward pass or adding computational overhead. We evaluate LibraGrad using three metric families: Faithfulness, which quantifies prediction changes under perturbations of the most and least relevant features; Completeness Error, which measures attribution conservation relative to model outputs; and Segmentation AP, which assesses alignment with human perception. Extensive experiments across 8 architectures, 4 model sizes, and 4 datasets show that LibraGrad universally enhances gradient-based methods, outperforming existing white-box methods -- including Transformer-specific approaches -- across all metrics. We demonstrate superior qualitative results through two complementary evaluations: precise text-prompted region highlighting on CLIP models and accurate class discrimination between co-occurring animals on ImageNet-finetuned models -- two settings on which existing methods often struggle. LibraGrad is effective even on the attention-free MLP-Mixer architecture, indicating potential for extension to other modern architectures. Our code is freely available at https://github.com/NightMachinery/LibraGrad.