“- and a phone call from Bill Gates of Microsoft offering him a job, which he turned down.”
Harnessing human computation
Luis von Ahn helped save the internet from spammers. His larger quest is to put internet chores to productive use
ONLY a few weeks into graduate school and aged just 22, Luis von Ahn helped crack one of the thorniest problems bedevilling the web.
It was the year 2000 and free, web-based e-mail services were booming. But spammers were creating thousands of accounts automatically and using them to blast out messages.
When the accounts were shut down, they simply created new ones. At the same time, sites selling tickets to concerts and sporting events were being besieged by programs that bombarded them with orders, snapping up the best seats for resale at a higher price.
Websites needed a way to distinguish between human visitors and automated ones.
Mr von Ahn had just arrived at Carnegie Mellon University in Pittsburgh when he and his PhD adviser, Manuel Blum, came up with just such a method.
The solution had three requirements: it had to be a test that humans could pass easily and computers could not—but could use computers to determine whether the response was correct. The original idea was to show web users an image, for example of a cat or a roller coaster, and ask them to identify it. A correct answer would indicate that the entity at the other end of the internet connection was indeed human, granting access to the web-mail service or ticketing site.
But it turned out that people were not very good at identifying images reliably.
So the pair came up with another idea: displaying a distorted sequence of letters and asking people to read them and type them into a box. This proved to be a much more reliable test of whether a visitor to a website was human or not (something that is known, in computer-science terminology, as a Turing test, in honour of Alan Turing, a British computer scientist). The result was the CAPTCHA, which stands for “Completely Automated Public Turing test to tell Computers and Humans Apart”. Yahoo and other web-mail providers implemented the system, and it immediately made life harder for spammers.
Mr von Ahn went on to get his doctorate—and a phone call from Bill Gates of Microsoft offering him a job, which he turned down.
He has since created a series of internet-based systems that bring many people together to perform useful work by dividing tasks into tiny pieces, often presented as a simple test or game, and aggregating the results. A decade ago Mr von Ahn called his approach “human computation” (the title of his thesis) and “games with a purpose”—precursors to the modern techniques of “crowdsourcing” and “gamification”.
Read Full Report: