This Is How to Tell if Writing Was Made by AI

What It Covers

Max Spiro, founder of Pangram Labs, explains how his AI detection platform achieves a 1-in-10,000 false positive rate by training deep learning models on tens of millions of paired human and AI writing samples, while approximately 40% of the current internet is already AI-generated content.

Key Questions Answered

• •AI Detection Accuracy: Pangram Labs achieves a false positive rate of 1 in 10,000 and a false negative rate of roughly 1%, far exceeding the ~90% human baseline accuracy. The model scales beyond simple perplexity metrics by using deep learning trained on millions of side-by-side human and AI writing pairs to detect subtle decision patterns.
• •How AI Writing Gets Detected: LLMs make thousands of micro-decisions when constructing even 100 words of text, and their output clusters into a narrow region of all possible writing. Pangram trains a model to recognize these decision patterns through contrast learning — pairing a human review with an AI-generated version of the same content to identify imperceptible differences.
• •Active Learning Pipeline: After an initial training pass on known human and AI samples, Pangram scans a larger corpus to surface false positives and false negatives, then feeds those edge cases back into retraining. This self-improving loop continuously pushes the model closer to the human-AI boundary where detection is hardest.
• •AI Slop Economics on Reddit: Startups sell services to brands promising organic-seeming AI bot mentions on Reddit, where bots post normal-seeming replies and occasionally name-drop products. This gaming matters because LLMs train on Reddit data, meaning seeded brand mentions in Reddit threads increase the likelihood those brands appear in future AI-generated responses.
• •Internet Contamination Scale: Roughly 40% of internet pages are now AI-generated, driven largely by SEO content farms switching to AI to produce keyword-targeting articles at near-zero cost. Medium crossed 50% AI-generated new articles roughly 18 months ago, while Reddit sits at around 10% today, up from 7% a year prior.