Lost in the Prompt Order: Revealing the Limitations of Causal Attention in Language Models

• URL: http://arxiv.org/abs/2601.14152v1
• Date: Tue, 20 Jan 2026 16:54:22 GMT
• Title: Lost in the Prompt Order: Revealing the Limitations of Causal Attention in Language Models
• Authors: Hyunjong Ok, Jaeho Lee,
• Abstract summary: Large language models exhibit surprising sensitivity to the structure of the prompt.<n>In multiple-choice question answering, placing context before the questions and options (CQO) outperforms the reverse order (QOC) by over 14%p.
• Score: 13.389832365304263
• License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/
• Abstract: Large language models exhibit surprising sensitivity to the structure of the prompt, but the mechanisms underlying this sensitivity remain poorly understood. In this work, we conduct an in-depth investigation on a striking case: in multiple-choice question answering, placing context before the questions and options (CQO) outperforms the reverse order (QOC) by over 14%p, consistently over a wide range of models and datasets. Through systematic architectural analysis, we identify causal attention as the core mechanism: in QOC prompts, the causal mask prevents option tokens from attending to context, creating an information bottleneck where context becomes invisible to options.

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