(How) Do MLLMs Report Bistable Images Like Humans?

Ryota Takatsuki, Tomoki Doi, Amane Watahiki, Anil K Seth, Hitomi Yanaka


Abstract
Bistable images such as the duck-rabbit are classic stimuli in which one image supports multiple mutually incompatible interpretations, typically reported one at a time in humans. We ask whether multimodal large language models (MLLMs) show similar report behavior and what internal computations support it. Using the LLaVA family, we study two tractable dimensions: modulability, whether reports can be biased by bottom-up visual cues and top-down linguistic priors, and exclusivity, whether responses commit to a single interpretation. We test both on the canonical duck-rabbit and on synthetic Visual Anagrams to mitigate memorization confounds. Behaviorally, both visual and linguistic manipulations systematically shift reports in human-consistent ways, while responses remain predominantly exclusive. Mechanistically, these effects arise from competing image-token representations, distinct pathways for bottom-up and top-down modulation, and a link between exclusive reporting and object-count encoding.
Anthology ID:
2026.emnlp-main.1744
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:
39784–39814
Language:
URL:
https://aclanthology.org/2026.emnlp-main.1744/
DOI:
Bibkey:
Cite (ACL):
Ryota Takatsuki, Tomoki Doi, Amane Watahiki, Anil K Seth, and Hitomi Yanaka. 2026. (How) Do MLLMs Report Bistable Images Like Humans?. In Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing, pages 39784–39814, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
(How) Do MLLMs Report Bistable Images Like Humans? (Takatsuki et al., EMNLP 2026)
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PDF:
https://aclanthology.org/2026.emnlp-main.1744.pdf