PathFinder: Discovering Decision Pathways in Deep Neural Networks

TL;DR

PathFinder introduces a method to interpret deep neural networks by identifying and visualizing common decision pathways through clustering activation patterns, aiding explainability and outlier detection.

Contribution

The paper presents a novel clustering-based approach to discover and visualize decision pathways in neural networks, enhancing interpretability of complex models.

Findings

Instances of the same class follow consistent cluster sequences.

Decision paths can identify outliers with unusual activation flows.

Sankey diagrams effectively visualize decision pathways.

Abstract

Explainability is becoming an increasingly important topic for deep neural networks. Though the operation in convolutional layers is easier to understand, processing becomes opaque in fully-connected layers. The basic idea in our work is that each instance, as it flows through the layers, causes a different activation pattern in the hidden layers and in our Paths methodology, we cluster these activation vectors for each hidden layer and then see how the clusters in successive layers connect to one another as activation flows from the input layer to the output. We find that instances of the same class follow a small number of cluster sequences over the layers, which we name ``decision paths." Such paths explain how classification decisions are typically made, and also help us determine outliers that follow unusual paths. We also propose using the Sankey diagram to visualize such pathways. We validate our method with experiments on two feed-forward networks trained on MNIST and CELEB data sets, and one recurrent network trained on PenDigits.