The simplicity of it is logic defying. It used to be that you had to find crosswalks or move puzzle pieces or type blurred letters and numbers, but NOW all the sudden I can just click a box and HEY!, I'm human?
That's hardly the Turing Test I'd expected.
This is correct. Those captchas are tracking everything they can and comparing it to other results to try and figure this out. Mouse movement, delay before you click, everything.