You desperately need a photo of a spider for a paper due tomorrow, so you search the Internet for a good image. Your search turns up all sorts of pictures, not only of spiders but also of sports cars, comic-book characters, card games, and other stuff.
A lot of the pictures are wrong because many of the billions of images on the Web aren't labeled very well. Some aren't labeled at all. And computers aren't very good at figuring out images, so they can't automatically create their own labels or find exactly what you're looking for.
You, on the other hand, have no trouble telling the difference between a tarantula and a sports car, even if the image is bad. So, what's the solution? Hire some people to start labeling images? That would cost too much, and they'd probably get bored pretty quickly. And even so, there'd be billions of unlabeled images.
Computer scientist Luis von Ahn of Carnegie Mellon University has come up with a great solution—and a playful one at that. He's turned the labeling of images into an Internet game, which he calls the ESP Game. To play von Ahn's game, you sign in at his Web site and get paired with another visitor. The two of you see the same image. Each of you then types in a word or phrase that describes the image. If the words match, both of you earn points. If the words don't agree, you keep on trying or switch to a new image. Your score is based on how many matches you get in 150 seconds.
Amazingly, von Ahn has found that people will spend hours playing this game, just to rack up points. No prizes. He collects the "winning" words or phrases, which then become keywords for the images. Von Ahn estimates that, given the popularity of his ESP Game in some tests, he could obtain labels for most of the Web's images in just a few weeks. Last fall, Google adopted von Ahn's idea and created its own label-making game.
Millions of people around the world spend hours playing computer solitaire every day, von Ahn says. So, why not harness all this game-playing energy and do something computers have a tough time doing on their own? Now, von Ahn is busy inventing new games to locate objects in images, write paragraphs to describe scenes, and collect commensense knowledge.
Who knows? The next game you play on the Internet may be useful as well as fun. And someday, you just might use a game like this to label all those digital photos you've stored and forgotten about on your computer.
Muse, March 2007, p. 37.
ESP Game: http://www.espgame.org/
Google Image Labeler: http://images.google.com/imagelabeler/
Top: Lynx spider. Photo by John R. Nickles/U.S. Fish & Wildlife Service
Bottom: The ESP Game. Courtesy of Luis von Ahn