Burstiness
A measure of variation in sentence length, structure, and complexity across a piece of text.
Burstiness is a measure of how much variation exists in sentence length, structure, and complexity across a piece of text. Human writing tends to be bursty: a long, winding sentence followed by a punchy short one, then a question, then a list. AI-generated writing is often the opposite — uniformly long, uniformly polished, uniformly mid.
Burstiness is one of the core signals AI detectors use. A piece of text with very low burstiness (high uniformity) raises the AI-probability score, all else equal. It's not definitive — some careful human writers are also uniform — which is why detectors combine burstiness with other signals.
Together with perplexity, burstiness forms the classic two-axis intuition behind many open-source AI detectors.
Related terms
- Perplexity— How surprised a language model is by a given piece of text — lower means the text looks more model-generated.
- AI detection— The task of identifying text that was written by a large language model rather than a human.
- Stylometry— The statistical analysis of writing style — historically used for author identification.
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