NLP Fundamentals
Burstiness
A measure of variation in sentence length and complexity across a passage. Human writing tends to be bursty; AI writing tends to be uniform.
Definition
Burstiness describes the natural ebb and flow in how humans construct passages — short punches followed by longer, layered sentences, then a fragment, then a question. Large language models trained on averaged human text tend to produce sentences clustered around a median length, with similar internal complexity. The difference is one of the most visible structural signals that text has been generated by a model rather than written by a person under deadline.
Why it matters
Editors and AI-detection systems alike rely on burstiness as a tell. A passage where every sentence is 18-24 words long, with two clauses connected by 'and' or 'while,' will register as machine-like even when individual word choices look fine. Conversely, a passage that opens with a four-word sentence, follows with a twenty-eight-word one, then breaks to a fragment, will read as alive — because that is how thinking sounds when someone is genuinely engaged. The edit is simple in principle. Read the draft aloud. Where rhythm flattens, break a long sentence in two, or merge two short ones into one. The goal is not random variation but the cadence of someone working through an idea.
Examples
Low burstiness
We value our customers. We aim to provide excellent service. We are committed to your satisfaction. We hope you enjoy your experience.
High burstiness
We care about the people who write to us. Not in a slogan way — in the way that means an actual person reads the reply before it goes out. That changes what we say.
Frequently asked
Is more burstiness always better?
No. Highly bursty writing can feel chaotic if every paragraph hits the same extremes. Skilled writing varies burstiness across the piece — patient explanation in one section, sharper rhythm in another.
Do detectors weigh burstiness or perplexity more?
Most modern detectors combine both, plus several proprietary signals. Burstiness alone is rarely decisive; it is one input among many.
How do I increase burstiness without sounding affected?
Cut every other long sentence in half. Let one short sentence land alone. Then stop — restraint is what makes the technique work.
Related terms
Perplexity
A measurement of how predictable a sequence of words is to a language model. Lower perplexity means the text follows patterns the model expects.
Humanization (of AI text)
The process of editing AI-generated writing so that it reads, scans, and lands as work by a thoughtful human author.
Sentence Rhythm
The pattern of sentence lengths and structures in a passage, which controls pacing and reader attention.
AI Detection
The practice of estimating, using statistical signals, whether a piece of text was produced by a language model rather than a human.
Put the concept to work
Open the rewrite engine and apply this principle to a draft of your own.
Try a rewrite