d’Olle Grieze at SemEval-2026 Task 11: Comparing the Impact of Supervised Fine-Tuning and Activation Steering on Mitigating Content Effect Bias in Syllogistic Reasoning

Twan Huiskens, Tian Niezing, Koen Snelten


Abstract
We investigate the content effect bias in Large Language Models (LLMs) as part of SemEval 2026 Task 11. We compare the impact of supervised fine-tuning using low-rank adaptation against activation steering across several model families, including LLaMA, Gemma and Qwen. Our results show that SFT improves accuracy, with LLaMa 8B reaching 98.75\% accuracy. Activation steering offers limited effectiveness in mitigating the content effect bias. A logit lens analysis further reveals that fine-tuning successfully shifts the model’s focus toward logical structure, specifically within the later layers.
Anthology ID:
2026.semeval-1.167
Volume:
Proceedings of the 20th International Workshop on Semantic Evaluation (2026)
Month:
July
Year:
2026
Address:
San Diego, California, USA
Editors:
Ekaterina Kochmar, Debanjan Ghosh, Kai North, Mamoru Komachi
Venues:
SemEval | WS
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
1268–1281
Language:
URL:
https://preview.aclanthology.org/ingest-acl-workshops/2026.semeval-1.167/
DOI:
Bibkey:
Cite (ACL):
Twan Huiskens, Tian Niezing, and Koen Snelten. 2026. d’Olle Grieze at SemEval-2026 Task 11: Comparing the Impact of Supervised Fine-Tuning and Activation Steering on Mitigating Content Effect Bias in Syllogistic Reasoning. In Proceedings of the 20th International Workshop on Semantic Evaluation (2026), pages 1268–1281, San Diego, California, USA. Association for Computational Linguistics.
Cite (Informal):
d’Olle Grieze at SemEval-2026 Task 11: Comparing the Impact of Supervised Fine-Tuning and Activation Steering on Mitigating Content Effect Bias in Syllogistic Reasoning (Huiskens et al., SemEval 2026)
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PDF:
https://preview.aclanthology.org/ingest-acl-workshops/2026.semeval-1.167.pdf
Supplementarymaterial:
 2026.semeval-1.167.SupplementaryMaterial.zip