Here is a key difference from prior CAPTCHA services :
"reCAPTCHA offers more than just spam protection. Every time our CAPTCHAs are solved, that human effort helps digitize text, annotate images, and build machine learning datasets. This in turn helps preserve books, improve maps, and solve hard AI problems.
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They're using captchas to solve text analysis and digitizing problems.
reCAPTCHA has been around in that form for a long time already. This post is about a new system they're planning on rolling out to replace that one. This one won't require any text input for (most) users.
"reCAPTCHA offers more than just spam protection. Every time our CAPTCHAs are solved, that human effort helps digitize text, annotate images, and build machine learning datasets. This in turn helps preserve books, improve maps, and solve hard AI problems. "
They're using captchas to solve text analysis and digitizing problems.