Inverting a solution to create another one

There's a great article in the July issue of Wired on CAPTCHA inventor Luis von Ahn. It chronicles his more recent work, about getting people to help solve problems that computers are bad at through networked video games. Instead of using the Internet to connect people to information, von Ahn conceptually inverts the scenario and applies a massive, free workforce to help computers organize information better.

Even if you don't know his name, you probably know von Ahn's work with CAPTCHAs. When you sign up for an online account somewhere, you are typically shown a graphic with morphed letters and asked to enter the sequence in a text box. That's a CAPTCHA. The intent is that there are some things that people can do which computers cannot. In order to prevent programs to automatically sign up for such services (like web-based email or ticket purchasing), CAPTCHAs insure a live person is there to decipher the morph that pattern recognition software cannot.

More recent CAPTCHAs, called reCAPTCHA, show two sequences of letters, but it isn't because doing so makes it more secure. As the Wired article reveals:

"The words are pulled from the book-scanning project of the Internet Archive, a nonprofit project in San Fransisco that aims to digitize millions of public-domain books and put them online for free. One of the two words in the test is the control word: The gatekeeper computer shows what it should be so, its there to make sure the puzzle-solver is indeed human. But the other word is there for a different reason. The Archive's scanners are good, but some of the words are too smudgy for the software to decipher. The game take the image of each smudgy word and puts into reCAPTCHA. Each time someone completes a reCAPTCHA puzzle, they'll be doing a tiny bit of work - translating that difficult image into text, which von Ahn eventually feeds back into the Archive."

So, instead of computers providing people with information, people are providing computers with information. This is the root of von Ahn's current work, which extends this concept to simple games, like The ESP Game which teams two anonymous players together. Each is shown a picture and asked to enter words to describe the picture. For every matching word, the team is awarded a point and given a score over a certain number of pictures. What appears to be a game is really involving humans to tag content that computers tend to interpret poorly.

All in all, von Ahn's work is an interesting field of story that takes the exact opposite approach you might think of to solve problems.

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