SYNTHESIS NOTE
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Why do language models fail at communicative optimization?

LLMs excel at learning surface statistical patterns from text but struggle with deeper principles of how language achieves efficient communication. What distinguishes these two types of linguistic knowledge?

Synthesis note · 2026-02-21 · sourced from Linguistics, NLP, NLU

"Do Large Language Models Resemble Humans in Language Use?" (Yiu et al. 2023) evaluates LLMs on a wide range of human linguistic regularities — not just grammaticality but psycholinguistic phenomena. The results show a consistent pattern of success and failure that tracks a specific distinction.

LLMs succeed on:

These regularities are learnable from distributional patterns in text — they appear consistently across large corpora and can be acquired through form-to-form prediction.

LLMs fail on:

These regularities require something beyond distributional pattern matching. They involve principles of why language works for communication — efficiency under communicative pressure, contextual interpretation that goes beyond local statistics, integration across discourse.

The discriminating principle: statistical regularities that appear as consistent patterns in training data transfer. Regularities that emerge from communicative optimization — the pragmatic logic of why language has the forms it does — do not transfer, because they are not present in surface form as trainable signals.

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This note is a source for these research framings, grouped by the broader line of inquiry each explores. Scan the bold lines of inquiry; follow any specific question forward.

Can language models reason beyond surface pattern matching? What prevents LLMs from applying their reasoning knowledge to improve outputs? Can LLMs distinguish between linguistic form and semantic meaning? Why do language models fail at sustained therapeutic relationships despite understanding techniques? Do language models encode knowledge that influences generation, or primarily imitate surface patterns? What limits language model accuracy in evaluating ideas? Do language models reason through disagreement or only accommodate it? What distinguishes genuine communicative competence from surface language performance? What causes coordination failures in multi-agent language model systems? When do simpler collaborative filtering approaches outperform complex LLM recommenders?

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Original note title

llms replicate local statistical regularities in language but fail to acquire communicative optimization principles