I shared this on my Google Reader, but I’d like to more formally share Luis Von Ahn’s great talk on the recaptcha.

Luis von Ahn at the Library of Congress via Luis von Ahn at the Library of Congress.

The talk covers the basics of a CAPTCHA (the hard-to-read words that verify you are human when signing up for online accounts) then discusses the recaptcha. The recaptcha pairs two random English words together so it can yield some funky phrases such as the “desert voter” shown below. (Watch the video for much better pairings!) The recaptcha uses one known word and one word that cannot be read by a machine. By distributing the otherwise unreadable word to multiple people, von Ahn is able to effortlessly digitize the written word. I respect and admire the ingenuity here. Dr. von Ahn simultaneously repels spammers and digitizes books!


This work provides two great insights to me: (1) humans are still better than computers at some things and (2) harnessing intelligence in a scalable way can have dramatic results. Want to make a mint? Figure out how to harness humans’ idle/unproductive time.