In a wonderful example of what Jeff Bezos describes as Artificial Artificial Intelligence researchers at Carnegie Mellon University have developed a system whereby words from old documents that cannot be read by OCR scanners are used as CAPTCHAs to prevent spamming ‘bots accessing websites, thereby simultaneously assisting in digitizing our written heritage and hindering malicious spammers, from the ScienceNOW article:
The team developed a new program, called reCAPTCHA, which collects words flagged as unreadable by optical scanners as they digitize texts. Those words, in the form of computer optical scans, are then sent to cooperating Web sites and used in place of random CAPTCHAs. The software presents one optically unreadable word and one “control” CAPTCHA word. Getting the control word right identifies the user as a human, and the program records his or her response to the unreadable word and adds it to a database.