Burstiness

Burstiness describes the uneven, irregular rhythm of human writing. Humans naturally write short punchy sentences alongside long, complex ones. We use fragments for emphasis. We stack clauses when making nuanced arguments. This variation — the 'burstiness' — is a strong human signal.

AI models tend toward uniform sentence length and structure. Ask ChatGPT to write a paragraph and you'll often get four to five sentences of roughly equal length, each following a predictable subject-verb-object pattern. Detectors measure this uniformity and flag it as an AI characteristic.

Burstiness is closely related to but distinct from perplexity. Perplexity measures word-level predictability; burstiness measures structural variation at the sentence and paragraph level. A text can have high perplexity (unusual words) but low burstiness (all sentences the same length) — and detectors will still flag it.

Injecting burstiness is a core humanization technique. This includes deliberately writing one-sentence paragraphs for emphasis, combining short declarative statements with longer analytical ones, and varying the syntactic structure of consecutive sentences. Good humanizers automate this structural variation while preserving meaning.