4arXiv cs.CL (Computation and Language)·
Linear representations of grammaticality found in neural language model internals
A new arXiv preprint investigates whether grammaticality is encoded in the internal representations of neural language models, moving beyond probability-based evaluations. Using mass-mean probing, the authors find that grammatical and ungrammatical sentences are robustly separated in representational space across a wide range of pretrained models, grammatical phenomena, and languages. The encoding is not fully explained by confounds like lexical frequency or plausibility, suggesting grammaticality constitutes a coherent representational dimension. The findings contribute to debates about syntactic knowledge in LLMs and offer a probability-independent framework for evaluating grammatical competence.
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Linear probes reveal LLMs encode remaining output length in hidden states
Researchers trained minimal linear probes on frozen hidden states of three open-weight 7-8B models and found that total response length is linearly decodable from the prompt's final hidden state before any output is generated. The probe directions transfer across natural-language and synthetic datasets, and per-position estimates shift upward when models retract and restart partial solutions. The authors interpret this as evidence that LLMs maintain a plan-like internal representation of remaining generation length, distinct from exact-counting, though causality is not established.
Tracing the Emergence of Human-Like Pragmatic Reasoning in LLMs Across Languages
Researchers conducted a population-matching experiment evaluating 25 LLMs on conditional inference tasks across four languages, comparing model behavior to matched human populations. The study finds that LLMs function as accurate semantic operators but systematically fail to capture pragmatic enrichments—context-sensitive inferences beyond literal logical meaning—that humans apply effortlessly. Model performance on pragmatic reasoning is not predicted by open vs. closed weights, training orientation, or architecture type, suggesting pragmatic reasoning remains an emergent and unreliable capability. The findings contribute to ongoing debates about whether LLMs reason like humans or merely approximate surface-level linguistic patterns.
Token probability measurements reveal production-perception asymmetry in LLMs
A new arXiv preprint investigates whether LLMs exhibit a functional analog to the psycholinguistic production-perception distinction, using direct token probability measurements rather than metalinguistic prompting. Using Llama-3.1-8B and four other open-weight models, the authors find that production-perception prompt distances consistently exceed production-production distances by a ratio of ~1.8, with near-ceiling correlations in the production-production control confirming the effect is specific to communicative framing. The effect replicates across five models spanning base and instruction-tuned variants, and temporal analysis shows perception prompts exert strongest influence at sequence beginnings. The findings suggest prompt framing alone induces a production-perception distinction in decoder-only architectures.
Mechanistic analysis of how LLMs encode essay quality in internal representations
Researchers systematically probe the hidden representations of eight LLMs across three essay datasets (ASAP++, CSEE, ENEM) to understand how automated essay scoring (AES) works internally. Using linear probing, dimensionality reduction, and neuron-level analysis, they find essay quality is encoded in a linearly accessible form that emerges progressively across layers and partially transfers across prompts. Individual 'essay scoring neurons' are identified whose activations correlate with scores and respond to targeted interventions, with longer essays relying more on deeper layers. The work contributes to mechanistic interpretability of LLM-based scoring systems.
Revisiting LLM systematicity in negation understanding via in-context learning
A new arXiv preprint analyzes how well large language models handle negation from two angles: behavioral systematicity (whether models correctly recognize negation expressions and scope) and representational systematicity (whether function vectors can be reliably constructed from in-context examples). Results show LLMs partially succeed at negation cue recognition via in-context learning but struggle with scope recognition, with performance varying by output format. Function vectors can be composed for cue extraction but are harder to extract for scope recognition tasks.
Mechanistic interpretability study reveals geometric structure of LLM-as-judge bias in hidden states
A new arXiv preprint investigates LLM-as-judge scoring bias at the representation level rather than the input-output level, studying seven judge models across seven bias types and nine benchmarks. The authors find that biased inputs are displaced along low-dimensional, type-specific subspaces in activation space, and that steering hidden states along these subspaces causally controls scoring direction. A linear projection onto bias-direction features predicts judge failures on unseen benchmarks, substantially outperforming text-based alternatives. The work provides a mechanistic account that unifies geometric structure, causal control, and operational prediction within a single framework.
Language Models Learn Constructional Semantics, Not To Mention Syntax: Investigating LM Understanding of Paired-Focus Constructions
This paper investigates whether language models can learn the semantics of rare English constructions (e.g., 'let alone', 'much less'), constructing a novel dataset to test form-meaning pairing understanding. Testing models across parameter counts, architectures, and pretraining dataset sizes, the authors find that modestly sized open-source models can grasp Paired-Focus construction semantics, while models trained on human-scale data fail. Training dynamics analysis reveals that semantic understanding of these constructions emerges later than syntactic knowledge and correlates with gains in world knowledge more broadly.
Survey chapter on LLM mechanisms, emergent capabilities, and cognition debates
A new arXiv preprint surveys current understanding of large language models, covering the Transformer architecture, emergent capabilities resembling human cognition (symbolic reasoning, theory of mind, deception), and explainability approaches from neuron activation analysis to circuit tracing. The chapter also engages the debate over whether LLMs genuinely understand or merely pattern-match, arguing against reductive anti-anthropomorphism while acknowledging human-LLM differences. It is framed as a book chapter synthesizing recent empirical findings and theoretical positions.