Humans Introduce, Models Elaborate: Asymmetric Narrative Agency in Human-LLM Co-Writing

Halfdan Nordahl Fundal, Yuri Bizzoni, Charlotte Gjørup Bilde, Ida Bække Johannesen, Rebekah Brita Baglini


Abstract
Human–LLM co-writing is increasingly used for open-ended text generation, but much prior work focuses on final outputs rather than the interactional dynamics through which stories are produced. We study turn-based collaborative storytelling across three matched conditions: Human–Human (HH), Human–AI (HA), and AI–AI (AA). Using a shared storytelling paradigm, we measure how agents align, introduce novel material, and influence narrative development through turn-level measures of valence adaptation, semantic novelty, transience, and resonance. Our results show that HA co-writing is not intermediate between HH and AA collaboration. Instead, it displays a distinctive asymmetry where humans tend to introduce more novel and persistent narrative material, while LLMs tend to elaborate and stabilize the existing context. These findings suggest that, in this setting, LLMs function less as human co-authors and more as adaptive narrative amplifiers that reshape how agency is distributed in collaborative writing.
Anthology ID:
2026.emnlp-main.2002
Volume:
Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Hung-Yi Lee, Sunipa Dev, Jessy Li, Desmond Elliott
Venue:
EMNLP
SIG:
SIGDAT
Publisher:
Association for Computational Linguistics
Note:
Pages:
45603–45617
Language:
URL:
https://aclanthology.org/2026.emnlp-main.2002/
DOI:
Bibkey:
Cite (ACL):
Halfdan Nordahl Fundal, Yuri Bizzoni, Charlotte Gjørup Bilde, Ida Bække Johannesen, and Rebekah Brita Baglini. 2026. Humans Introduce, Models Elaborate: Asymmetric Narrative Agency in Human-LLM Co-Writing. In Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing, pages 45603–45617, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Humans Introduce, Models Elaborate: Asymmetric Narrative Agency in Human-LLM Co-Writing (Fundal et al., EMNLP 2026)
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PDF:
https://aclanthology.org/2026.emnlp-main.2002.pdf