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Found in the Middle: Calibrating Positional Attention Bias Improves Long Context Utilization

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arxiv 2406.16008 v2 pith:V4UNGYPW submitted 2024-06-23 cs.CL cs.AIcs.LG

classification cs.CLcs.AIcs.LG
keywords attentionbiasinputllmslongmiddlecontextcontexts
verification ladder T0 review T1 audit T2 compute T3 formal
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Large language models (LLMs), even when specifically trained to process long input contexts, struggle to capture relevant information located in the middle of their input. This phenomenon has been known as the lost-in-the-middle problem. In this work, we make three contributions. First, we set out to understand the factors that cause this phenomenon. In doing so, we establish a connection between lost-in-the-middle to LLMs' intrinsic attention bias: LLMs exhibit a U-shaped attention bias where the tokens at the beginning and at the end of its input receive higher attention, regardless of their relevance. Second, we mitigate this positional bias through a calibration mechanism, found-in-the-middle, that allows the model to attend to contexts faithfully according to their relevance, even though when they are in the middle. Third, we show found-in-the-middle not only achieves better performance in locating relevant information within a long context, but also eventually leads to improved retrieval-augmented generation (RAG) performance across various tasks, outperforming existing methods by up to 15 percentage points. These findings open up future directions in understanding LLM attention bias and its potential consequences.

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Cited by 6 Pith papers

Reviewed papers in the Pith corpus that reference this work. Sorted by Pith novelty score. Full citation record

  1. MHA-RAG: Improving Efficiency, Accuracy, and Consistency by Encoding Exemplars as Soft Prompts

    cs.AI 2025-10 conditional novelty 6.0 of 10

    MHA-RAG encodes retrieved exemplars into order-invariant soft prompts via multi-head attention, claiming ~20-point effective-accuracy gains over RAG at ~10x lower inference FLOPs.

  2. Mitigating Posterior Salience Attenuation in Long-Context LLMs with Positional Contrastive Decoding

    cs.CL 2025-06 conditional novelty 6.0 of 10

    Positional Contrastive Decoding, a training-free method that contrasts standard and over-rotated RoPE logits, improves long-context retrieval and QA by a few points.

  3. Seed-Coder: Let the Code Model Curate Data for Itself

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    Seed-Coder shows that an LLM-trained quality scorer can filter 6T tokens of code data and yield 8B models that outperform similar-size open code models.

  4. FaithfulRAG: Fact-Level Conflict Modeling for Context-Faithful Retrieval-Augmented Generation

    cs.CL 2025-06 conditional novelty 5.0 of 10

    FaithfulRAG resolves knowledge conflicts in RAG by extracting the model's parametric facts, aligning them with context, and reasoning through discrepancies before generating an answer.

  5. Small Encoders Can Rival Large Decoders in Detecting Groundedness

    cs.CL 2025-06 conditional novelty 4.0 of 10

    Task-specific encoders (e.g., RoBERTa-large) rival large decoders such as Llama-3-8B and GPT-4o on binary groundedness detection, within 5 to 10 accuracy points while requiring one to three orders of magnitude fewer FLOPs.

  6. Evaluating and Improving Robustness in Large Language Models: A Survey and Future Directions

    cs.CL 2025-06 conditional novelty 3.0 of 10

    LLM robustness research is organized into adversarial robustness, out-of-distribution robustness, and evaluation, with an accompanying GitHub collection of papers.

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