Can you spot the watermarked LLM output? Take the quiz
Guess which of these LLM outputs is watermarked
A new quiz challenges readers to identify which of three LLM responses was generated with Google DeepMind's SynthID text watermark. Ten prompts, each with three responses, one watermarked. The quiz tests whether humans can detect the subtle statistical watermark embedded in AI-generated text.
Can you spot the watermark?
- bastawhiz
I've read that watermarking should in theory be impossible to detect except by the entity that watermarked it. Which is sensible, and I mostly understand at a high level.
But what I don't know and don't understand is what happens if you watermark watermarked text. Does it test positive for both watermarks? Only the second? Indeterminate?
Or maybe I'm misunderstanding. Can you tell that it's watermarked, but only the entity who put the watermark in place can test if it's theirs? My confusion about watermarking multiple times still stands, though.
Regardless of what happens when you watermark multiple times, no matter the outcome, it weakens the watermark. Which, depending on the threat model, kind of makes it moot. I can't imagine a serious situation where a watermark can be weakened in any way and still be useful. Even "this came from an LLM" isn't a valid signal if you can just watermark ANY text through purely mechanical means.
It's also not clear to me how this will affect mainstream LLMs. If all output text is watermarked, there MUST be an escape hatch. Otherwise, JSON schemas will break (or provide holes where unwatermarked text can be exfiltrated through MCP), "return this text exactly with no changes" will be impossible, and writing diffs will break.
I feel like I must be missing something.
- Noumenon72
Please report success/failure after each test. Asking me to read and compare 30 writing samples to get any feedback at all means I won't finish. Telling me immediately when I got one wrong lets me recognize patterns and improve my guesses.
- abathur
My sense of the concern here is that watermarking may somehow deprive someone or something of value regardless of whether or not they can tell, so I briefly pondered trying to rank these from best to worst and see if any set of those votes meaningfully deviated from ~average.
That said, I read the first triple and found all three tortured enough that I can't be bothered with the rest.
Call me persuaded, I guess.
- reactordev
Wow I actually got a 7/10. It was hard to tell at first but there are signs that tipped me off to which one probably had a higher score out of the multiple choice.
- fwlr
Utterly imperceptible, even when studied under the microscope in a way that LLM text very rarely is in practice.
It will be interesting to see whose concerns are assuaged (perhaps they genuinely though mistakenly believed it would degrade quality), and whose concerns are heightened (perhaps their real objection is that their AI-generated text will become detectable).