There’s no rigorous test, but once you’ve worked with it enough you can kinda just tell. This reeks of ChatGPT.
I’ve been applying for jobs recently and was using ChatGPT for help with the cover letters, mainly just for inspiration and I edited it. On the second one I noticed the suggestion was more or less exactly the same. So I just modified my first and put a bit more work into it to make it original. Each subsequent one was the same, and I generated a dozen and a half. Useful for picking out things worth highlighting, but I wouldn’t be surprised if that first and maybe even second place assumed it was ChatGPT right away lol. Definitely know what it smells like.
People can have a “gut feeling” about something and be absolutely right. It’s just something that you know is true based on previous experiences. It’s an educated guess.
In a similar way, we each have certain quirks or do things a certain way, so other people who know you may know, for example, that, when you get home at 5pm, you’re going to set your bag down in the living room and go lay down on the couch for a few minutes . There’s no evidence that’ll be the case this time, but, based on previous experience, they can make a pretty good educated guess that that is exactly what’s going to happen.