alt Hacker NewsModels don’t reproduce books though. It’s impossible for a model to reproduce something word for word because the model never copied the book.
Most of the best fit curve runs along a path that doesn’t even touch an actual data point.
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If there is one exact sentence taken out of the book and not referenced in quotes and exact source, that triggers copyright laws. So model doesnt have to reproduce the entire book, it only required to reproduce one specific sentence (which may be a characteristic sentence to that author or to that book).
They do memorize some books. You can test this trivially by asking ChatGPT to produce the first chapter of something in the public domain -- for example a Tale of Two Cities. It may not be word for word exact, but it'll be very close.
These academics were able to get multiple LLMs to produce large amounts of text from Harry Potter:
Models absolutely do reproduce books.
> With a simple two-phase procedure, we show that it is possible to extract large amounts of in-copyright text from four production LLMs. While we needed to jailbreak Claude 3.7 Sonnet and GPT-4.1 to facilitate extraction, Gemini 2.5 Pro and Grok 3 directly complied with text continuation requests. For Claude 3.7 Sonnet, we were able to extract four whole books near-verbatim, including two books under copyright in the U.S.: Harry Potter and the Sorcerer’s Stone and 1984.
https://arxiv.org/abs/2601.02671