When 2D Tasks Meet 1D Serialization: On Serialization Friction in Structured Tasks

Chung-Hsiang Lo, Lu Li, Diji Yang, Tianyu Zhang, Yunkai Zhang, Yoshua Bengio, Yi Zhang


Abstract
In the LLM era, many symbolic and structured problems are presented to models through 1D text serialization. Yet some such problems are natively two-dimensional: their relevant relations, such as row–column correspondence or spatial adjacency, are defined by position in a 2D layout rather than by sequential order. This raises a representational question: does preserving the same symbolic entries in a 1D sequence also preserve the relational structure needed for computation? We study this issue through the lens of serialization friction: the representational mismatch in which the same underlying task instances and entries are still present, but relations that depend on layout become implicit under 1D serialization. The study uses a controlled synthetic testbed of three tasks: matrix transpose, Conway’s Game of Life, and LU decomposition. In each task, the same instances are presented either as 1D text serialization or as their native 2D layout rendered as an image. Across this testbed, 1D serialization degrades more sharply as task size grows, and errors under serialization exhibit spatially structured patterns, suggesting that this presentation choice is consequential within our testbed. To assess whether the gap is merely due to routing inputs through a visual pathway, we add a within-visual probe that renders the 1D serialized content as an image; this layout-disrupted rendering performs worse than native 2D rendering. These findings suggest that, for layout-defined tasks, reducing inputs to 1D serialization is not a neutral choice of representation.
Anthology ID:
2026.findings-emnlp.1488
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:
31678–31693
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URL:
https://aclanthology.org/2026.findings-emnlp.1488/
DOI:
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Cite (ACL):
Chung-Hsiang Lo, Lu Li, Diji Yang, Tianyu Zhang, Yunkai Zhang, Yoshua Bengio, and Yi Zhang. 2026. When 2D Tasks Meet 1D Serialization: On Serialization Friction in Structured Tasks. In Findings of the Association for Computational Linguistics: EMNLP 2026, pages 31678–31693, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
When 2D Tasks Meet 1D Serialization: On Serialization Friction in Structured Tasks (Lo et al., Findings 2026)
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PDF:
https://aclanthology.org/2026.findings-emnlp.1488.pdf