arXiv AI By Kiyan Rezaee

The Illusion of Replacement: Rethinking Specialized Machine Learning Models in the Foundation Model Era

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arXiv AI
Oct 16

Language Models Struggle to Use Representations Learned In-Context

The article examines whether large language models (LLMs) can effectively use representations they learn in-context to perform downstream tasks. Experiments with open‑weight LLMs on next‑token prediction and a new adaptive world modeling task reveal that these models struggle to deploy novel semantics defined in-context, even when such semantics are encoded in their latent representations. The study also shows that state‑of‑the‑art closed‑source reasoning models similarly fail to reliably leverage in‑context patterns, highlighting a gap in flexible representation usage.

By Michael A. Lepori, Tal Linzen, Ann Yuan, Katja Filippova
arXiv Computation and Language
Oct 22

StructLens: A Structural Lens for Language Models via Maximum Spanning Trees

StructLens is a framework that analyzes language model representations by constructing maximum spanning trees from semantic representations in residual streams, inspired by dependency parsing. It reveals that contiguous tokens are close in representation space, with middle layers showing the strongest local-span organization. The study also shows that smaller local units emerge earlier during pre‑training, while larger units appear later, offering insights into how token representations are organized across layers and training stages.

By Haruki Sakajo, Frederikus Hudi, Yusuke Sakai, Hidetaka Kamigaito, Taro Watanabe