AI RESEARCH
More Thinking, More Bias: Length-Driven Position Bias in Reasoning Models
arXiv CS.AI
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ArXi:2605.06672v1 Announce Type: new Chain-of-thought (CoT) reasoning and reasoning-tuned models such as DeepSeek-R1 are commonly assumed to reduce shallow heuristic biases by thinking carefully. We test this on position bias in multiple-choice QA and find a different story: within any reasoning-capable model, per-question position bias scales with the length of the reasoning trajectory.