Mixture of Tunable Experts -- Behavior Modification of DeepSeek-R1 at Inference Time

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Main Authors: Dahlke, Robert, Klagges, Henrik, Zecha, Dan, Merkel, Benjamin, Rohr, Sven, Klemm, Fabian
Format: Preprint
Published: 2025
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author Dahlke, Robert
Klagges, Henrik
Zecha, Dan
Merkel, Benjamin
Rohr, Sven
Klemm, Fabian
author_facet Dahlke, Robert
Klagges, Henrik
Zecha, Dan
Merkel, Benjamin
Rohr, Sven
Klemm, Fabian
contents We present the Mixture-of-Tunable-Experts (MoTE), a method that extends the Mixture-of-Experts architecture of Large Language Models (LLMs). Without additional training, MoTE enables meaningful and focused behavior changes in LLMs on-the-fly during inference time. By analyzing the digital LLM brain of DeepSeek-R1 using a technique we dub 'functional Token Resonance Imaging' (fTRI) -- inspired by fMRI and using prompts designed to elicit specific behavior (e.g., 'What happened {time}{place}?') -- we empirically identify distinctive experts associated with behaviors like refusal responses. Using MoTE we are able to intervene and control such specific behavior. We switched off the top 10 most refusal-relevant experts (0.07% of R1's 14,848 routed experts), achieving a 52% refusal reduction on sensitive reference prompts without performance degradation on MT-Bench. Random expert deactivation resulted in smaller behavioral shifts with increased noise, whereas forced expert activation led to significantly higher refusal rates. Our approach shares similarities with sparse autoencoders (SAEs) in terms of explainability and steerability. Unlike SAEs, MoTE does not require large training efforts, as within MoEs with a vast number of experts, specialization already emerged naturally during pretraining. Our findings suggest that significant functional mechanisms in Mixture-of-Experts architectures can at least partially be localized in a small number of specific experts, rather than being distributed throughout the model's weights. Expert subgroups can be tuned to trigger significant behavior variations, providing insights into the inner workings of LLMs.
format Preprint
id arxiv_https___arxiv_org_abs_2502_11096
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Mixture of Tunable Experts -- Behavior Modification of DeepSeek-R1 at Inference Time
Dahlke, Robert
Klagges, Henrik
Zecha, Dan
Merkel, Benjamin
Rohr, Sven
Klemm, Fabian
Artificial Intelligence
Computation and Language
We present the Mixture-of-Tunable-Experts (MoTE), a method that extends the Mixture-of-Experts architecture of Large Language Models (LLMs). Without additional training, MoTE enables meaningful and focused behavior changes in LLMs on-the-fly during inference time. By analyzing the digital LLM brain of DeepSeek-R1 using a technique we dub 'functional Token Resonance Imaging' (fTRI) -- inspired by fMRI and using prompts designed to elicit specific behavior (e.g., 'What happened {time}{place}?') -- we empirically identify distinctive experts associated with behaviors like refusal responses. Using MoTE we are able to intervene and control such specific behavior. We switched off the top 10 most refusal-relevant experts (0.07% of R1's 14,848 routed experts), achieving a 52% refusal reduction on sensitive reference prompts without performance degradation on MT-Bench. Random expert deactivation resulted in smaller behavioral shifts with increased noise, whereas forced expert activation led to significantly higher refusal rates. Our approach shares similarities with sparse autoencoders (SAEs) in terms of explainability and steerability. Unlike SAEs, MoTE does not require large training efforts, as within MoEs with a vast number of experts, specialization already emerged naturally during pretraining. Our findings suggest that significant functional mechanisms in Mixture-of-Experts architectures can at least partially be localized in a small number of specific experts, rather than being distributed throughout the model's weights. Expert subgroups can be tuned to trigger significant behavior variations, providing insights into the inner workings of LLMs.
title Mixture of Tunable Experts -- Behavior Modification of DeepSeek-R1 at Inference Time
topic Artificial Intelligence
Computation and Language
url https://arxiv.org/abs/2502.11096