> The idea behind reCAPTCHA is that it occasionally throws in a word (or street sign, or occasional fragment of total garbage) that it doesn't know. Yes, but y

> The idea behind reCAPTCHA is that it occasionally throws in a word (or street sign, or occasional fragment of total garbage) that it doesn't know. Yes, but you don't have to input those. Try it for yourself and see. (I never input them.) When you do input them, it helps Google digitize books, street numbers, etc.--sort of like a "Mechanical Turk"--but it's completely optional. So you could devise a text-to-speech algorithm, but only for the word Google's CAPTCHA actually knows. (It's probably in the works as we speak.)