Whether you're a professor checking student work or a content editor reviewing submissions, being able to spot AI-written text is an increasingly important skill. Here are the five most reliable signs — and how to fix them if you're a writer whose work is being flagged.
1. Uniform Sentence Length
AI-generated text tends to have remarkably uniform sentence lengths. If you measure the word count of every sentence in an AI-written paragraph, you'll find they cluster tightly around 15-25 words. Human writing, by contrast, varies dramatically — from 2-word fragments to 40-word complex sentences.
AI text sentence lengths: 18, 22, 19, 21, 20, 23, 18, 22
Human text sentence lengths: 5, 34, 12, 28, 3, 41, 15, 22
AI standard deviation: ~2.1 words
Human standard deviation: ~12.4 wordsAfter writing, scan your text for sentence length variation. Intentionally add some very short sentences (3-5 words) and some long ones (30+ words). Break up any sequence of 3+ sentences that are all similar length.
2. Overuse of Transition Words
AI models love transition words. "Furthermore," "moreover," "additionally," "consequently," "in conclusion" — these appear far more frequently in AI text than in human writing. Real writers use transitions more sparingly and more naturally.
Watch for these AI-favorite transitions:
- "Furthermore" — appears 3x more often in AI text
- "Moreover" — appears 4x more often in AI text
- "Additionally" — appears 3.5x more often in AI text
- "Consequently" — appears 2.5x more often in AI text
- "In conclusion" — appears 5x more often in AI text
- "It is worth noting that" — almost exclusively AI
- "It is important to note that" — almost exclusively AI
Search your text for these transition words and replace most of them. Instead of "Furthermore, the data shows..." try "The data also shows..." or just start the sentence directly. Instead of "In conclusion," try "The bottom line is..." or "Here's what this means."
3. Lack of Specific Examples
AI text tends to stay abstract. It makes general claims without backing them up with specific, concrete examples. This is because AI models generate the most statistically likely next sentence, and general statements are more predictable than specific ones.
AI: "Many students struggle with time management
when writing research papers."
Human: "When I was writing my senior thesis, I
spent three weeks just on the literature review
because I kept going down rabbit holes instead
of staying focused on my research question."
The human version is specific, personal, and
memorable. The AI version could be about anyone.After every general claim, ask: "Can I add a specific example?" If you're writing about a concept, include a real-world case. If you're making an argument, include a specific scenario. Personal anecdotes are especially effective.
4. Perfect Grammar and Uniform Structure
AI text is grammatically perfect. Every sentence is complete. Every paragraph has a topic sentence and a concluding sentence. Every essay follows the same structure. This perfection is itself a tell — human writing is messier.
Real human writing includes:
- Sentence fragments. Sometimes. For effect.
- Sentences that start with "And" or "But" or "Because."
- Paragraphs that don't have clear topic sentences.
- Occasional run-on sentences that pack multiple ideas together.
- Rhetorical questions that don't have obvious answers.
- Parenthetical asides (like this one) that reflect the writer's thinking process.
Don't over-edit your writing. Leave some natural imperfections. Start a sentence with "But." Use a fragment for emphasis. Add a parenthetical aside. These "imperfections" are what make writing feel human.
5. Hollow Empathy and Generic Engagement
AI text often includes phrases that sound empathetic but are actually hollow: "I understand this can be challenging," "It's important to remember that," "Don't worry — you're not alone." These phrases are statistically common in AI output because they're safe, non-committal, and universally applicable.
Real empathy is specific. Instead of "I understand this can be challenging," a human writes: "When I faced this problem, I spent two days debugging before I realized I'd misspelled a variable name. That's the kind of challenge this is — not hard, just frustrating."
Cut every generic empathy phrase. Replace each one with a specific observation, a real example, or a concrete piece of advice. If you can't be specific, just remove the phrase — it's adding nothing.
Quick Self-Check
Before submitting or publishing, run this 5-point check on your text:
- Are your sentence lengths varied? (Check for 3+ consecutive sentences of similar length)
- Have you used "furthermore," "moreover," or "additionally" more than once?
- Does every claim have a specific example or anecdote?
- Is your writing grammatically perfect with no fragments or creative structures?
- Are there generic empathy phrases that could apply to anyone?
If you answered "yes" to any of these, your text may read as AI-like — even if you wrote every word yourself. Fix the issues using the tips above, or run your text through HumanAI's humanizer to automatically introduce natural variation.
