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🐻Berkeley BAIR
March 13, 2026
Research

Identifying Interactions at Scale for LLMs

Overview

This Berkeley BAIR post introduces SPEX and ProxySPEX, algorithms designed to identify influential interactions in large machine learning systems, including large language models, at scale. It frames the work within interpretability research, which seeks to make model decision-making more transparent for safer and more trustworthy AI. The core challenge is that the number of possible interactions grows exponentially, making exhaustive analysis infeasible, so SPEX uses ideas from signal processing and coding theory to find the small set of interactions that truly drive behavior.

Key Takeaways

  • --> Understanding the behavior of complex machine learning systems, particularly Large Language Models (LLMs), is a critical challenge in modern artificial intelligence.

    Interpretability research aims to make the decision-making process more transparent to model builders and impacted humans, a step toward safer and more trustworthy AI.

  • Therefore, grounded or reality-checked interpretability methods must also be able to capture these influential interactions .

    As the number of features, training data points, and model components grow, the number of potential interactions grows exponentially, making exhaustive analysis computationally infeasible.

  • Data Attribution: We train models on different subsets of the training set, assessing how the model's output on a test point shifts in the absence of specific training data.

    Model Component Attribution (Mechanistic Interpretability): We intervene on the model's forward pass by removing the influence of specific internal components, determining which internal structures are responsible for the model's prediction.

  • SPEX and ProxySPEX Framework To discover influential interactions with a tractable number of ablations, we have developed SPEX (Spectral Explainer).

    This framework draws on signal processing and coding theory to advance interaction discovery to scales orders of magnitude greater than prior methods.

  • Then, using efficient decoding algorithms, we disentangle these combined signals to isolate the specific interactions responsible for the model's behavior.
Identifying Interactions at Scale for LLMs

--> Understanding the behavior of complex machine learning systems, particularly Large Language Models (LLMs), is a critical challenge in modern artificial intelligence. Interpretability research aims to make the decision-making process more transparent to model builders and impacted humans, a step toward safer and more trustworthy AI. Across these perspectives, the same fundamental hurdle persists: complexity at scale .

Model behavior is rarely the result of isolated components; rather, it emerges from complex dependencies and patterns. To achieve state-of-the-art performance, models synthesize complex feature relationships, find shared patterns from diverse training examples, and process information through highly interconnected internal components. Therefore, grounded or reality-checked interpretability methods must also be able to capture these influential interactions .

As the number of features, training data points, and model components grow, the number of potential interactions grows exponentially, making exhaustive analysis computationally infeasible. In this blog post, we describe the fundamental ideas behind SPEX and ProxySPEX , algorithms capable of identifying these critical interactions at scale. Attribution through Ablation Central to our approach is the concept of ablation , measuring influence by observing what changes when a component is removed.

For more details please read the original article at Berkeley BAIR.

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Originally published by Berkeley BAIR
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