Do Large Language Models Have “Emotion Neurons”? Investigating the Existence and Role

Jaewook Lee, Woojin Lee, Oh-Woog Kwon, Harksoo Kim


Abstract
This study comprehensively explores whether there actually exist “emotion neurons” within large language models (LLMs) that selectively process and express certain emotions, and what functional role they play. Drawing on the representative emotion theory of the six basic emotions, we focus on six core emotions. Using synthetic dialogue data labeled with emotions, we identified sets of neurons that exhibit consistent activation patterns for each emotion. As a result, we confirmed that principal neurons handling emotion information do indeed exist within the model, forming distinct groups for each emotion, and that their distribution varies with model size and architectural depth. We then validated the functional significance of these emotion neurons by analyzing whether the prediction accuracy for a specific emotion significantly decreases when those neurons are artificially removed. We observed that in some emotions, the accuracy drops sharply upon neuron removal, while in others, the model’s performance largely remains intact or even improves, presumably due to overlapping and complementary mechanisms among neurons. Furthermore, by examining how prediction accuracy changes depending on which layer range and at what proportion the emotion neurons are masked, we revealed that emotion information is processed in a multilayered and complex manner within the model.
Anthology ID:
2025.findings-acl.806
Volume:
Findings of the Association for Computational Linguistics: ACL 2025
Month:
July
Year:
2025
Address:
Vienna, Austria
Editors:
Wanxiang Che, Joyce Nabende, Ekaterina Shutova, Mohammad Taher Pilehvar
Venue:
Findings
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
15617–15639
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URL:
https://preview.aclanthology.org/display_plenaries/2025.findings-acl.806/
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Bibkey:
Cite (ACL):
Jaewook Lee, Woojin Lee, Oh-Woog Kwon, and Harksoo Kim. 2025. Do Large Language Models Have “Emotion Neurons”? Investigating the Existence and Role. In Findings of the Association for Computational Linguistics: ACL 2025, pages 15617–15639, Vienna, Austria. Association for Computational Linguistics.
Cite (Informal):
Do Large Language Models Have “Emotion Neurons”? Investigating the Existence and Role (Lee et al., Findings 2025)
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PDF:
https://preview.aclanthology.org/display_plenaries/2025.findings-acl.806.pdf