[olegk]

You have no idea what you're talking about.

> show a picture of an animal or a shape and ask what it is,

Ok, so let's say you come up with pictures of 20 different animals. A spam script that picks the same answer every time will have a 5% success rate.

> or even just ask a simple math problem or riddle in writing.

Computers are way better at solving most math problems than people.

[raganwald]

You have no idea what you're talking about.

Please be careful. It could be that his thoughts are excellent but his communication is flawed. It could also be that he has a great deal of general expertise in the subject but is mistaken in this specific statement.

Thus, a general statement about him could be false is also aggressively ad hominem. You might want to consider focusing on the statement itself rather than the speaker, such as:

"Your suggestion is entirely wrong."

JM2C of course, and it is possible that I don't know what I'm talking about. I am not a psychologist or a logician.

[mseebach]

Please read my post. Specifically the second paragraph where exactly this issue is addressed.

[olegk]

Still doesn't make sense.

If you display 10 random animals (or shapes), and ask a user to pick the right one, a dumb spam script would have a 10% success rate.

If you display one image of an animal and give 10 possible answers, a dumb spam script would have a 10% success rate.

[mseebach]

So if I have a library of 10s of thousands of images of animals, shapes, things etc. that are all easily recognisable to English speakers -- e.g. cat, dog, house, drum, road, tree, book, horse -- and ask them to write in what is it, AND I constantly update that library and retire pictures that's been used many time -- what is your dumb script's success rate?

What if I combine three pictures in each challenge - e.g. "cat house triangle"?

[olegk]

My spam script would always answer "cat", so among 8 options (cat, dog, house, drum, road, tree, book, horse), I'd get a 12.5% success rate.

Plus you constantly have to update your image library, which a huge pain.

Also, recognizing 10,000 images will take me around one day and less than $1000 with Amazon turk, thus giving me a perfect 100% success rate. After that you would have to completely renew your image database.

[mseebach]

sigh .. etc. There would be more than 8 options, many more.

YES, it would be a pain to update the library, which is why I'm commending this particular concept for solving that problem ...

[StavrosK]

You aren't getting it. The probability is 1/<number of options you present to the user>. If you show the user 100 images and ask them to select one, a bot will have a 1% probability to find the right one, but the user will tell you to get lost.

If you present 10 images (still a stretch), bots will have 10% success rate just answering randomly.

EDIT: Wait, from what I see you mean that the user will have to write "cat" or "dog" or whatever? That's better, yes. Communication, however, is hard, which is why me the GP didn't understand what you meant.