Here is a brief explanation from the site:
When you play a game at Gwap, you aren't just having fun. You're helping the world become a better place. By playing our games, you're training computers to solve problems for humans all over the world.
Von Ahn has made a career (and earned a MacArthur Fellowship) from his work on such games, most notably the ESP Game and reCAPTCHA. His games emphasize tagging tasks that are difficult for machines but easy for human beings, such as labeling images with high-level descriptors.
I've been interested in Von Ahn's work for several years, and most particularly in a game called Phetch, a game which never quite made it out of beta but strikes me as one of the most ambitious examples of "human computation". Here is a description from the Phetch site:
Quick! Find an image of Michael Jackson wearing a sailor hat.
Phetch is like a treasure hunt -- you must find or help find an image from the Web.
One of the players is the Describer and the others are Seekers. Only the Describer can see the hidden image, and has to help the Seekers find it by giving them descriptions.
If the image is found, the Describer wins 200 points. The first to find it wins 100 points and becomes the new Describer.
A few important details that this description leaves out:
- The Seeker (but not the Describer) has access to search engine that has indexed the images based on results from the ESP Game.
- A Seeker loses points (I can't recall how many) for wrong guesses.
- The game has a time limit (hence the "Quick!").
Now, let's unpack the game description and analyze it in terms of the Human-Computer Information Retrieval (HCIR) paradigm. First, let us simplify the game, so that there is only one Seeker. In that case, we have a cooperative information retrieval game, where the Describer is trying to describe a target document (specifically, an image) as informatively as possible, while the Seeker is trying to execute clever algorithms in his or her wetware to retrieve it. If we think in terms of a traditional information retrieval setup, that makes the Describer the user and the Seeker the information retrieval system. Sort of.
A full analysis of this game is beyond the scope of a single blog post, but let's look at the game from the Seeker's perspective, holding our assumption that there is only one Seeker, and adding the additional assumption that the Describer's input is static and supplied before the Seeker starts trying to find the image.
Assuming these simplifications, here is how a Seeker plays Phetch:
- Read the description provided by the Describer and uses it to compose a search.
- Scan the results sequentially, interrupting either to make a guess or to reformulate the search.
The key observation is that Phetch is about interactive information retrieval. A good Seeker recognizes when it is better to try reformulating the search than to keep scanning.
Returning to our theme of evaluation, we can envision modifying Phetch to create a system for evaluating interactive information retrieval. In fact, I persuaded my colleague Shiry Ginosar, who worked with Von Ahn on Phetch and is now a software engineer at Endeca, to elaborate such an approach at HCIR '07. There are a lot of details to work out, but I find this vision very compelling and perhaps a route to addressing Nick Belkin's grand challenge.