Interpreting the Repeated Token Phenomenon in Large Language Models

Fuente: arXiv
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Auteurs principaux: Yona, Itay, Shumailov, Ilia, Hayes, Jamie, Barbero, Federico, Gandelsman, Yossi
Format: Preprint
Publié: 2025
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author Yona, Itay
Shumailov, Ilia
Hayes, Jamie
Barbero, Federico
Gandelsman, Yossi
author_facet Yona, Itay
Shumailov, Ilia
Hayes, Jamie
Barbero, Federico
Gandelsman, Yossi
contents Large Language Models (LLMs), despite their impressive capabilities, often fail to accurately repeat a single word when prompted to, and instead output unrelated text. This unexplained failure mode represents a vulnerability, allowing even end-users to diverge models away from their intended behavior. We aim to explain the causes for this phenomenon and link it to the concept of ``attention sinks'', an emergent LLM behavior crucial for fluency, in which the initial token receives disproportionately high attention scores. Our investigation identifies the neural circuit responsible for attention sinks and shows how long repetitions disrupt this circuit. We extend this finding to other non-repeating sequences that exhibit similar circuit disruptions. To address this, we propose a targeted patch that effectively resolves the issue without negatively impacting the model's overall performance. This study provides a mechanistic explanation for an LLM vulnerability, demonstrating how interpretability can diagnose and address issues, and offering insights that pave the way for more secure and reliable models.
format Preprint
id arxiv_https___arxiv_org_abs_2503_08908
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Interpreting the Repeated Token Phenomenon in Large Language Models
Yona, Itay
Shumailov, Ilia
Hayes, Jamie
Barbero, Federico
Gandelsman, Yossi
Machine Learning
Artificial Intelligence
Computation and Language
Cryptography and Security
Large Language Models (LLMs), despite their impressive capabilities, often fail to accurately repeat a single word when prompted to, and instead output unrelated text. This unexplained failure mode represents a vulnerability, allowing even end-users to diverge models away from their intended behavior. We aim to explain the causes for this phenomenon and link it to the concept of ``attention sinks'', an emergent LLM behavior crucial for fluency, in which the initial token receives disproportionately high attention scores. Our investigation identifies the neural circuit responsible for attention sinks and shows how long repetitions disrupt this circuit. We extend this finding to other non-repeating sequences that exhibit similar circuit disruptions. To address this, we propose a targeted patch that effectively resolves the issue without negatively impacting the model's overall performance. This study provides a mechanistic explanation for an LLM vulnerability, demonstrating how interpretability can diagnose and address issues, and offering insights that pave the way for more secure and reliable models.
title Interpreting the Repeated Token Phenomenon in Large Language Models
topic Machine Learning
Artificial Intelligence
Computation and Language
Cryptography and Security
url https://arxiv.org/abs/2503.08908