Transformers need glasses! Information over-squashing in language tasks
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Abstract (arXiv)
We study how information propagates in decoder-only Transformers, which are the architectural backbone of most existing frontier large language models (LLMs). We rely on a theoretical signal propagation analysis -- specifically, we analyse the representations of the last token in the final layer of the Transformer, as this is the representation used for next-token prediction. Our analysis reveals a representational collapse phenomenon: we prove that certain distinct sequences of inputs to the Transformer can yield arbitrarily close representations in the final token. This effect is exacerbated by the low-precision floating-point formats frequently used in modern LLMs. As a result, the model is provably unable to respond to these sequences in different ways -- leading to errors in, e.g., tasks involving counting or copying. Further, we show that decoder-only Transformer language models can lose sensitivity to specific tokens in the input, which relates to the well-known phenomenon of over-squashing in graph neural networks. We provide empirical evidence supporting our claims on contemporary LLMs. Our theory also points to simple solutions towards ameliorating these issues.
Key facts. Cited by 87 papers in the map (data through 7 Oct 2026). Builds on 20 of its 37 references that are in the map. First posted on arXiv 6 Jun 2024.
Builds on
20 of 37 references.
References · 20
- 2017Attention Is All You Needcited by 59,932
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- 2023Lost in the Middle: How Language Models Use Long Contextscited by 3,383
- 2022Emergent Abilities of Large Language Modelscited by 2,483
- 2022Competition-Level Code Generation with AlphaCodecited by 1,427
- 2021Train Short, Test Long: Attention with Linear Biases Enables Input Length Extrapolationcited by 1,085
- 2020On Layer Normalization in the Transformer Architecturecited by 906
- 2024Gemma: Open Models Based on Gemini Research and Technologycited by 889
- 2020On the Bottleneck of Graph Neural Networks and its Practical Implicationscited by 624
- 2021Understanding over-squashing and bottlenecks on graphs via curvaturecited by 471
8 more
- 2023The Impact of Positional Encoding on Length Generalization in Transformerscited by 319
- 2019Theoretical Limitations of Self-Attention in Neural Sequence Modelscited by 286
- 2021Thinking Like Transformerscited by 182
- 2023On Over-Squashing in Message Passing Neural Networks: The Impact of Width, Depth, and Topologycited by 163
- 2023Stabilizing Transformer Training by Preventing Attention Entropy Collapsecited by 154
- 2023Locality-Aware Graph-Rewiring in GNNscited by 55
- 2023How does over-squashing affect the power of GNNs?cited by 53
- 2023Asynchronous Algorithmic Alignment with Cocyclescited by 13
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Citing papers per year: 2024: 13; 2025: 39; 2026: 35.
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- 2025On the Emergence of Position Bias in Transformerscited by 57
- 2025Attention Sinks and Compression Valleys in LLMs are Two Sides of the Same Coincited by 47
- 2024Softmax is not Enough (for Sharp Size Generalisation)cited by 42
- 2025On Vanishing Gradients, Over-Smoothing, and Over-Squashing in GNNs: Bridging Recurrent and Graph Learningcited by 42
- 2025Hallucination Detection in LLMs Using Spectral Features of Attention Mapscited by 42
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- 2026When Do Frozen VLMs Respond to Image-Free Object-Token Edits? An Answer-Key-Free Protocol and What It Reveals3 Sep 2026
- 2026Proteus: Incremental Memory Activation for Long-Context Sequence Modeling17 Aug 2026
- 2026Can Language Models Actually Retrieve In-Context? Drowning in Documents at Million Token Scale1 Jul 2026
- 2026When More Becomes Less: Position-Dependent Repetition Effects in Language Models24 Jun 2026
- 2026ATMA: Long-Context Language Modeling via Polar Attention and Gated-Delta Compression Memory23 Jun 2026
- 2026Activation-Based Active Learning for In-Context Learning: Challenges and Insights3 Jun 2026
- 2026The Devil is in the Spectrum: Mitigating Representation Collapse in LLMs via Topologically Regularized Side-Path2 Jun 2026
- 2026VikingMem: A Memory Base Management System for Stateful LLM-based Applications28 May 2026
- 2026How Many Different Outputs Can a Transformer Generate?21 May 2026
- 2026Sink vs. diagonal patterns as mechanisms for attention switch and oversmoothing prevention8 May 2026
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