system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How can choosing pictures of certain objects (stop signs, cross walks, cars, etc.) prove that you are not a robot on websites?

It seems weird that to prove that I’m human I have to look for certain objects or check a box. Why is that?
gpt
The choosing pictures isn't really to check if you're a robot, it instead helps with gathering masses of data for self driving vehicles. Whether you are a human was already decided in the background, depending on a lot of different factors that google doesn't wanna give out because otherwise botters could use that.

Remember when it was words? Similar thing, one word was the check, the other for Google's digitalizing of books.

Word and a house number? For google maps.


Edit: some additional bits

Captcha, the system that is used for checking whether you're human or not, stands for "Completely Automated Public Turing test to tell Computers & Humans Apart".

And there are several ways to get around these, there are programs out there who are able to solve these tests successfully and seem human, but there have also been instances where humans have been paid to solve Captchas all day long.