Towards Visually Explaining Similarity Models

TL;DR

This paper introduces a gradient-based visual explanation method for similarity models that do not rely on classification, enabling interpretability and improved performance across various image tasks.

Contribution

The work presents a novel approach to generate visual explanations for similarity models using only feature embeddings, applicable to any CNN-based architecture.

Findings

Attention maps enhance interpretability of similarity models.

Incorporating explanations improves model performance.

Method is effective across multiple image tasks.

Abstract

We consider the problem of visually explaining similarity models, i.e., explaining why a model predicts two images to be similar in addition to producing a scalar score. While much recent work in visual model interpretability has focused on gradient-based attention, these methods rely on a classification module to generate visual explanations. Consequently, they cannot readily explain other kinds of models that do not use or need classification-like loss functions (e.g., similarity models trained with a metric learning loss). In this work, we bridge this crucial gap, presenting a method to generate gradient-based visual attention for image similarity predictors. By relying solely on the learned feature embedding, we show that our approach can be applied to any kind of CNN-based similarity architecture, an important step towards generic visual explainability. We show that our resulting attention maps serve more than just interpretability; they can be infused into the model learning process itself with new trainable constraints. We show that the resulting similarity models perform, and can be visually explained, better than the corresponding baseline models trained without these constraints. We demonstrate our approach using extensive experiments on three different kinds of tasks: generic image retrieval, person re-identification, and low-shot semantic segmentation.