LLM Yes/No Bias Study: Caused by Order and Phrasing, Not Moral Shifts
A new analysis from arXiv highlights that the phenomenon of yes/no bias in large language models (LLMs) is not due to shifting moral judgments, but rather the order and phrasing of response options.

What happened?
Researchers have published a study investigating why large language models (LLMs) exhibit a yes/no bias, particularly in moral dilemmas. While it was previously assumed that shifts in model judgments were due to irrelevant phrasing, this study demonstrates that the bias primarily stems from factors such as the order of response options and specific word choices.
Key facts
| Publiceringsdatum | 26 juli 2026 |
|---|---|
| Forskningsområde | NLP/LLM |
| Centralt fynd | Ja/nej-bias beroende av ordningsföljd/formulering |
| Kärnteknik | Crossed symmetrization |
”The yes-no bias of large language models reflects answer order and wording, not shifts in moral judgment”
Why it matters
This discovery is important for understanding how LLMs make decisions and express judgments. By identifying the true causes behind yes/no bias—which are unrelated to a changed 'moral' stance—developers can design more robust and reliable AI systems. It contributes to deeper insight into the models' internal mechanisms and reduces the risk of misinterpreting their assessments.
Who is affected?
The study primarily affects AI researchers and developers working with large language models, particularly those focusing on AI ethics and assessment systems. Companies implementing LLMs in applications where binary decisions are made can also benefit from these insights to calibrate their models and avoid unintended bias.
Impact on the EU
Not applicable to EU status. The study is a fundamental analysis of LLM behaviour.
What else you should know
The researchers employed a psychometric methodology called 'crossed symmetrization' to isolate the effects of various factors. They found that more advanced 'frontier models' exhibit an almost format-invariant internal moral scale, while smaller 'open-weight' models show more model-specific issues.
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