Sunday, February 4, 2007

Mechanical Turk: The Search for Jim Gray


Computer Scientist Jim Gray has been missing at sea since January 28 after he didn't return from a trip to the Farallon Islands in his yacht.

After the Coast Guard failed to find him, a satellite scan was performed and the images were posted to Amazon's Mechanical Turk.

The fact that you can join the search for Jim Gray is, I think, a wonderful sign of the power of technology to both equip people and to help them organize around common goals.

Being the weirdo that I am, my next thought was, "How can you get more people to join in?", and I immediately thought of a technique for circumventing CAPTCHAs using porn surfers that my friends and I discussed. This porn CAPTCHA idea has surfaced independently on a post by another blogger, titled The Power of Porn.

Imagine it: "Yes, yes, we'll get right to the T-n-A, but first, please check this satellite image for indications of foreign objects..."

Of course, one of the problems with this approach lies in a critical difference between this and CAPTCHA problems. CAPTCHA solving problems are effectively supervised learning problems -- the answer can be checked immediately, and if the spammer gets an error message instead of the free email account (or whatever), then they can try again. The case of examining satellite imagery for foreign objects is unsupervised, in that, if a participant happens to miss the little speck of sail boat in the picture, or just blindly clicks an answer to get to the porn, then there's no easy way to check it.

One solution to this problem is a critical part of Mechanical Turk -- test problems. For the satellite imagery problem, you first inject one or more test pictures, which you have specially created and know whether there is a foreign object present. Then you can test participants and grade them before you send them the real thing.

I'm telling you, there's power in harnessing the collective intelligence.

1 comment:

Andy said...

I forgot to mention the ties to projects like SETI@home.