Decomposition of Small Transformer Models

Fuente: arXiv
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Auteurs principaux: Christensen, Casper L., Riggs, Logan
Format: Preprint
Publié: 2025
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author Christensen, Casper L.
Riggs, Logan
author_facet Christensen, Casper L.
Riggs, Logan
contents Recent work in mechanistic interpretability has shown that decomposing models in parameter space may yield clean handles for analysis and intervention. Previous methods have demonstrated successful applications on a wide range of toy models, but the gap to "real models" has not yet been bridged. In this work, we extend Stochastic Parameter Decomposition (SPD) to Transformer models, proposing an updated causal importance function suited for sequential data and a new loss function. We demonstrate that SPD can successfully decompose a toy induction-head model and recover the expected 2-step circuit. We also show that applying SPD to GPT-2-small can successfully locate subcomponents corresponding to interpretable concepts like "golf" and "basketball". These results take the first step in the direction of extending SPD to modern models, and show that we can use the method to surface interpretable parameter-space mechanisms.
format Preprint
id arxiv_https___arxiv_org_abs_2511_08854
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Decomposition of Small Transformer Models
Christensen, Casper L.
Riggs, Logan
Machine Learning
Recent work in mechanistic interpretability has shown that decomposing models in parameter space may yield clean handles for analysis and intervention. Previous methods have demonstrated successful applications on a wide range of toy models, but the gap to "real models" has not yet been bridged. In this work, we extend Stochastic Parameter Decomposition (SPD) to Transformer models, proposing an updated causal importance function suited for sequential data and a new loss function. We demonstrate that SPD can successfully decompose a toy induction-head model and recover the expected 2-step circuit. We also show that applying SPD to GPT-2-small can successfully locate subcomponents corresponding to interpretable concepts like "golf" and "basketball". These results take the first step in the direction of extending SPD to modern models, and show that we can use the method to surface interpretable parameter-space mechanisms.
title Decomposition of Small Transformer Models
topic Machine Learning
url https://arxiv.org/abs/2511.08854