Some Emotions Run Deeper: Layer-wise Probing and Causal Intervention in Large Language Models

Tian Fang, Gaël Guibon, Davide Buscaldi


Abstract
Emotion is expressed in text along a wide spectrum, from surface lexical cues to inferences entangled with content. Most layer-wise analyses of emotion in LLMs use a single corpus, leaving open whether the depth at which emotion becomes accessible is a property of the model or also of the text source. We investigate this across three datasets spanning different degrees of explicitness and contextualization in emotion expression (Twitter posts, Reddit comments, and autobiographical narratives) and eight 1B–9B open-weight LLMs from the Llama, Qwen, and Granite families. We combine layer-wise probing with offline feature scaling and online forward interventions, transfer analyses, and an early-exit classifier. We find that (i) the best probing layer shifts systematically across corpora, from input-adjacent layers to over half model depth, and this ordering persists after matching label-by-length-bin distributions; (ii)across the evaluated settings, forward-pass interventions on probe-selected bands reduce test accuracy by 5–6 points more than same-width random bands (q < 0.01); (iii) selected bands transfer across datasets and emotion categories, suggesting partially shared affective information rather than strictly per-emotion substrates; and (iv) probe-selected early-exit representations outperform full-depth exits by 6.9 percentage points on average.
Anthology ID:
2026.findings-emnlp.421
Volume:
Findings of the Association for Computational Linguistics: EMNLP 2026
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Hung-Yi Lee, Sunipa Dev, Jessy Li, Desmond Elliott
Venue:
Findings
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SIGDAT
Publisher:
Association for Computational Linguistics
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Pages:
8858–8876
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URL:
https://aclanthology.org/2026.findings-emnlp.421/
DOI:
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Cite (ACL):
Tian Fang, Gaël Guibon, and Davide Buscaldi. 2026. Some Emotions Run Deeper: Layer-wise Probing and Causal Intervention in Large Language Models. In Findings of the Association for Computational Linguistics: EMNLP 2026, pages 8858–8876, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Some Emotions Run Deeper: Layer-wise Probing and Causal Intervention in Large Language Models (Fang et al., Findings 2026)
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https://aclanthology.org/2026.findings-emnlp.421.pdf