Luis von Ahn

Luis von Ahn
Born	1978 Guatemala City, Guatemala
Alma mater	Carnegie Mellon University Duke University
Scientific career
Institutions	Carnegie Mellon University
Doctoral advisor	Manuel Blum

Luis von Ahn (born in 1978 in Guatemala City, Guatemala) is an assistant professor in the Computer Science Department at Carnegie Mellon University, where he also received his Ph.D. in 2005 under the supervision of Manuel Blum. Previously, von Ahn obtained a B.S. in mathematics from Duke University in 2000. He is the recipient of a Microsoft Research Fellowship, and became a MacArthur Fellow (a.k.a., the "genius award") in 2006. His research includes CAPTCHAs and Human-based computation. He studied at the American School of Guatemala.

Von Ahn's early work was in the field of cryptography. With Nick Hopper and John Langford, he was the first to provide rigorous definitions of steganography and to prove that private-key steganography is possible. He has also worked with the cryptographer Josh Benaloh.

In 2000, he did early work in CAPTCHA, a computer-generated test that humans can pass but computers cannot. The device is used by websites to prevent bots from automatically registering large numbers of accounts. The CAPTCHA brought Luis his first widespread fame among the general public due to its coverage in The New York Times, USA Today, Discovery Channel, and other mainstream outlets.

His Ph.D. thesis, completed in 2005, was the first treatise recognizing the importance of human-based computation within computation generally. It is also the first work on Games with a Purpose, which are games played by humans that produce useful computation as a side-effect. The most famous example is the ESP Game, a game in which two people are simultaneously given an image of the same picture, with no way to communicate. Each then lists a number of words/phrases that describe the picture within a time limit, and are rewarded with points for a match. This match turns out to be an accurate description of the picture, and can be successfully employed in a database for more accurate image search technology. The ESP Game has been licensed by Google in the form of the Google Image Labeler, and is used to improve the accuracy of the Google Image Search. Other games include Peekaboom, a game for locating objects within an image, Verbosity, a game for collecting common-sense facts about the world, and Phetch, a game for annotating web images with explanatory text. Von Ahn's games brought him more coverage in the mainstream media, as well as numerous honors including the MacArthur Fellowship, Microsoft New Faculty Fellowship, Technology Review's TR35: Young Innovators Under 35, and Popular Science Magazine's Brilliant 10. His thesis won the Best Doctoral Dissertation Award from Carnegie Mellon University's School of Computer Science.

More recently, von Ahn developed reCAPTCHA, a new form of CAPTCHA that also helps digitize books. In reCAPTCHA, the words displayed to the user come directly from old books that are being digitized; they are words that OCR could not identify and are sent to people throughout the Web to be identified.

Controversies

Some of von Ahn's unconventional teaching techniques have become the source of controversy. In the fall of 2008, he taught a new course entitled "Science of the Web".[1] One of the homework assignments in this class was to get as many people as possible to visit a particular web site.[2] This resulted in many accusations of spamming, as students repeatedly advertised this web site. Another assignment was to get web pages with the term "rankmaniac" ranked as highly as possible on Google.[3] This also resulted in accusations of spamming.

Von Ahn again rose to controversy in January 2009, with a homework assignment which he called "Giramacristo's Puzzle".[4] This name was chosen because at the time it did not appear in any search engine indexes. Prior to giving the assignment, von Ahn posted the solution on his web site mathpuzzlesgallore.org, and submitted the URL to various search engines.[5] He then recorded the IP addresses which accessed this web site and compared them to those of students who had accessed the course web site. Any student suspected of having looked at the answer received a failing grade.

External links

• Luis von Ahn's Blog
• Web page at CMU
• Lecture on human computation by Luis von Ahn
• Google Image Labeler
• John D. and Catherine T. MacArthur foundation