Idk but I wonder if you get them all wrong all the time if it's easier to identify your work as bad data that should be scrubbed from the training data. Would a better strategy be to get most right and some wrong so you appear as normal user

Most people seem to just half-brain the challenges anyway. So on images where its easy to confuse something, the tests will often refuse you unless you put in the wrong answer, just like everybody else.

nah they're probably past that stage already. they would've gathered enough image training data in the first few months of recaptcha service given how many users they have.