Punctuation and Predicates in Language Models

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Main Authors: Chauhan, Sonakshi, Chaudhary, Maheep, Choy, Koby, Nellessen, Samuel, Schoots, Nandi
Format: Preprint
Published: 2025
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author Chauhan, Sonakshi
Chaudhary, Maheep
Choy, Koby
Nellessen, Samuel
Schoots, Nandi
author_facet Chauhan, Sonakshi
Chaudhary, Maheep
Choy, Koby
Nellessen, Samuel
Schoots, Nandi
contents In this paper we explore where information is collected and how it is propagated throughout layers in large language models (LLMs). We begin by examining the surprising computational importance of punctuation tokens which previous work has identified as attention sinks and memory aids. Using intervention-based techniques, we evaluate the necessity and sufficiency (for preserving model performance) of punctuation tokens across layers in GPT-2, DeepSeek, and Gemma. Our results show stark model-specific differences: for GPT-2, punctuation is both necessary and sufficient in multiple layers, while this holds far less in DeepSeek and not at all in Gemma. Extending beyond punctuation, we ask whether LLMs process different components of input (e.g., subjects, adjectives, punctuation, full sentences) by forming early static summaries reused across the network, or if the model remains sensitive to changes in these components across layers. Extending beyond punctuation, we investigate whether different reasoning rules are processed differently by LLMs. In particular, through interchange intervention and layer-swapping experiments, we find that conditional statements (if, then), and universal quantification (for all) are processed very differently. Our findings offer new insight into the internal mechanisms of punctuation usage and reasoning in LLMs and have implications for interpretability.
format Preprint
id arxiv_https___arxiv_org_abs_2508_14067
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Punctuation and Predicates in Language Models
Chauhan, Sonakshi
Chaudhary, Maheep
Choy, Koby
Nellessen, Samuel
Schoots, Nandi
Computation and Language
Machine Learning
In this paper we explore where information is collected and how it is propagated throughout layers in large language models (LLMs). We begin by examining the surprising computational importance of punctuation tokens which previous work has identified as attention sinks and memory aids. Using intervention-based techniques, we evaluate the necessity and sufficiency (for preserving model performance) of punctuation tokens across layers in GPT-2, DeepSeek, and Gemma. Our results show stark model-specific differences: for GPT-2, punctuation is both necessary and sufficient in multiple layers, while this holds far less in DeepSeek and not at all in Gemma. Extending beyond punctuation, we ask whether LLMs process different components of input (e.g., subjects, adjectives, punctuation, full sentences) by forming early static summaries reused across the network, or if the model remains sensitive to changes in these components across layers. Extending beyond punctuation, we investigate whether different reasoning rules are processed differently by LLMs. In particular, through interchange intervention and layer-swapping experiments, we find that conditional statements (if, then), and universal quantification (for all) are processed very differently. Our findings offer new insight into the internal mechanisms of punctuation usage and reasoning in LLMs and have implications for interpretability.
title Punctuation and Predicates in Language Models
topic Computation and Language
Machine Learning
url https://arxiv.org/abs/2508.14067