# Lost in the Middle

> Lost in the middle is the finding that language models use information at the beginning or end of a long context much more reliably than information placed in the middle.

- Identifier: PTL-0098
- Category: Failure Modes & Evaluation
- Canonical URL: https://protologue.com/t/lost-in-the-middle/
- Also known as: positional bias, U-shaped context performance
- Introduced: 2023

## Description

Liu et al. observed a U-shaped performance curve on multi-document question answering as the position of the relevant document varied. A practical takeaway is to place key material and instructions at the start or end of long prompts.

## Related terms

- [Context Window](https://protologue.com/t/context-window/)
- [Needle in a Haystack](https://protologue.com/t/needle-in-a-haystack/)
- [Context Engineering](https://protologue.com/t/context-engineering/)
- [Thread of Thought](https://protologue.com/t/thread-of-thought/)

## Sources

- Liu et al. (2023). Lost in the Middle: How Language Models Use Long Contexts. https://arxiv.org/abs/2307.03172

## Cite this entry

Protologue. (2026). Lost in the Middle. In Protologue: A Taxonomy of Prompting and LLM Techniques (v1.0.0, PTL-0098). https://protologue.com/t/lost-in-the-middle/

License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/)