Luis von Ahn: Expert Q&A

  • Posted 07.06.09
  • NOVA scienceNOW

On July 6, 2009, computer scientist and gaming enthusiast Luis von Ahn answered questions about his work and life, including the deeper meaning of the Trogdor on his office door. 

Luis von Ahn

Luis von Ahn

Luis von Ahn is Assistant Professor of Computer Science at Carnegie Mellon University. Full Bio

Photo credit: Courtesy Carnegie Mellon University

Luis von Ahn

Luis von Ahn is Assistant Professor of Computer Science at Carnegie Mellon University. Much of his work focuses on finding novel ways to harness the unique computational abilities of humans to solve complex, large-scale problems. (See and for examples.) His research interests also include human-computer interaction, artificial intelligence, and cryptography and security. In addition to receiving a MacArthur Fellowship, von Ahn has been dubbed one of the "50 Best Brains in Science" by Discover magazine and one of Popular Science's "Brilliant 10 Scientists of 2006." When he was a video-game-playing kid in Guatemala City, his favorite Street Fighter avatar was Ken.

Q: In what other fields do you think that Turing tests would be useful to the world of computing (other than for security and transcription of words computers cannot read)? What is next in the future of human/PC interaction from your view in computer science? Blaze A. Hauser, Houston, Texas

Luis von Ahn: We're working on making them be useful for transcribing audio and recognizing the contents of general images. The idea is the same as reCAPTCHA: We give each human two problems—one for which the system has already figured out the answer, and one for which it doesn't know the answer.

Q: I noticed on the nameplate to your door that you have a picture of "Trogdor" the Burninator. I'm a big fan of Trogdor. What significance does that hold in your professional life? It's very rare to see a Trogdor. Alec I., Grand Rapids, Michigan

von Ahn: There is no significance other than me being a big fan of Strongbad. :)

Q: Do ethics play a role in your vision of the future of user utilization? Should millions of users' time and energy only be used for common-interest goals like digitizing the Library of Congress, or should corporations be allowed to basically "outsource" many of their data-entry projects to the Internet, and if so, is that in our best interests? Anonymous

von Ahn: This is a very good question. All my projects try to accomplish public good, and in all cases we do not hide the real motive of the system—reCAPTCHA's slogan, for example, is "Stop Spam, Read Books."

On the other hand, as the Web evolves, more and more "Web 2.0" sites obtain work or information from their users and extract monetary gain out of it. For example, entering a book review, rating a movie, filling out a profile, uploading or tagging a photograph—all generate revenue for Web 2.0 sites.

Q: What would you say to other young Latinos to encourage them to enter fields of STEM (Science, Technology, Engineering and Math)? I think you are a great example for all! Albert Castillo, Chicago, Illinois

von Ahn: Thank you! I've never been good at talking people into entering any field of study. Perhaps I should try harder, but my philosophy has always been to do great work and rely on my actions to do the talking. I guess all I can say is: "I love my job!"

Q: Dude! =)
Do you believe in "singularity?" (I'm skeptical myself.) Stated differently, how far away are we from compilers/CAD tools/etc. improving themselves via architectural improvements (hw/sw/machine-learning) with minimal human intervention? Eric Anderson, Palo Alto, California

von Ahn: I believe that one day computers will be able to do everything human beings can do. I don't know if they'll be able to feel the same way we do, but I think that from the outside they'll be equivalent to or better than us.

Q: I had to solve two reCAPTCHAs yesterday to e-mail Washington Post articles to family. In both, I recognized the first word easily enough, but the second totally stymied me. I did the best I could, and when I was allowed to send the article, I assumed I got it right. (I didn't know about the book digitization aspect yet.)

reCAPTCHA assumes that the person typing in the information is getting it right, but does anyone check on the back end? Is there another program to run spell check once the CAPTCHAs are solved? Is there any way to check that the information is correct, or will humanity end up with digitized books with several mistakes? Or do you consider that the advantage of getting so many books digitized overwhelmingly outweighs the disadvantage of marginal mistakes? Thanks! Anonymous

von Ahn: We use many mechanisms to prevent mistakes. One of them is giving each word to multiple humans; we only assume an answer is correct if multiple people have entered it. We also use a sophisticated spell-checker that knows what the most likely word is given all the words around it; for example, it knows that "fancy blue jeans" is a lot more natural than "fancy glue jeans." At the end of the day, the accuracy of text digitized with reCAPTCHA is about 99.6 percent at the word level, which is much better than the approximately 75 percent obtained without using reCAPTCHA.

Q: Computer science students today are exposed to a multitude of variant forms of computer application (UI design, algorithms, cryptography, etc.), unlike anything in the 1960s or 1970s. How is a student supposed to navigate such a rich field when opportunities are easy to miss? Vahan Hartooni, Irvine, California

von Ahn: Very good question. I don't know the answer. :)

Q: Hello,
I am studying Web design, and I like to produce fractal animations. I love TV also. I am a member of Phi Theta Kappa. My question is, I got peripheral neuropathy in my feet, and I spend a lot of time in bed bored with thoughts of what can I do to make the world a better place with my laptop. Is there anything that I can be working on in relation to projects for computer science? I am very bright, but since I got sick, I have all this time, but nothing to really work on that is pushing computers or the Internet envelope. I really want to contribute to this, even if it was just brainstorming over what works with something visual or doesn't. I just want to feel useful. Scott Finnell, Fleming Island, Florida

von Ahn: The Web is perfect for you! Although I am fortunate to have my health, I spend most of my time in front of a computer. Think of what it would have been like for you 30 years ago. You'd be stuck watching TV all day long. Make cool stuff and contribute it on the Web!

Q: Dr. von Ahn, how many users does a word being identified by reCAPTCHA have to be verified by before it is accepted? Andrew Spearman, Tupelo, Mississippi

von Ahn: It depends on the word. On average each word is given to about five users, but some require only two to three users and others require about 10.

Q: CAPTCHA is a great idea, especially with archiving publications!

My question is, do you think mysteries could be deciphered by the masses, such as CAPTCHA was able to do with the archiving process? For instance, could an unsolved mystery be solved if it were placed in an online video game with all the evidence, circumstances, etc. laid out for the masses to play/work through? Each would add their own discovery, helping in others' discoveries and ultimately solving the mystery. In many video games, one has to search out the clues to find the key that will lead them to the next level. Do you think that same principle could be applied to helping solve cold case murders or phenomena? April Sanchez, Austin, Texas

von Ahn: I have no idea how to do this, but it would be awesome if we could figure it out!

Q: As a child, were you ever labeled autistic, genius, or any other term to describe your fantastic and amazing powers of thinking, reasoning, and problem-solving? Anonymous

von Ahn: I was only labeled "hyperactive."

Q: Has any work been done toward finding ways to make something like recycling a "game"? Here's the problem: Only about 5 percent of the people on our street "do the right thing" and recycle. How could the government create incentives for something like recycling not only paper and plastic but computers?

The only thing that comes to my mind is to make it a sort of lottery. When people would insert the correct kind of item into containers in a recycling center, they would be given a ticket that would enter them into a weekly prize of a large amount of money. Timothy Hamilton, St. Louis, Missouri

von Ahn: I have not thought about this, but it's certainly worth thinking about it.

Q: Brainstorming about the book project: Couldn't you get volunteer school districts, and have the students type a specific amount of words? It could qualify as "service learning" or community service. Teachers could give points for typing a paragraph and then have students analyze a specific part of the paragraph. Or each district could get recognition for the typing. This might be idiotic.... Anonymous

von Ahn: Perhaps we could get some volunteers, but I think there are better things they could be doing with their time. We already decipher so many words per day (tens of millions) that volunteers probably would not make much of a difference.

Q: What is your favorite part of life at CMU? Alan Desmarais, West Hartford, Connecticut

von Ahn: The people.

Q: Hi,

I am currently doing an undergraduate degree in biomedical engineering at the University of Calgary. I saw your profile on the show, and I can't stop looking at our similarities. I am a TV/video games addict, love computer programming, and plan on getting a Ph.D. as well.

I do the same things when I am looking for solutions to problems. I walk around hallways. Don't think about anything else except for it. I am also a musician; I play the guitar. I was wondering if you played an instrument as well? Also, when I do problem-solving, it interferes with what I normally do and frustrates people around me such as parents, etc. because I can't focus on anything else. I was wondering if you had the same issues as well?

Would love to hear from you. Tan, Department of Geomatics and Biomedical Engineering, University of Calgary, Calgary, Alberta, Canada

von Ahn: Unfortunately, I do not play any instruments. :( I do, however, play Guitar Hero.

And yes, when I work on a project I stop paying attention to other things. That's why I became a professor: I can spend my time working on anything I want.

Q: How has your background in mathematics helped you in computer science? Anonymous

von Ahn: It has helped me A LOT. I think a background in mathematics can help in almost any field or profession because it helps you think more clearly.

Q: Has CAPTCHA proven its effectiveness for its original intent? Has there been a noticeable or measured decline in Spam? How would you judge its success? Daniel Crocker, Boston, Massachusetts

von Ahn: Every major site in the world uses a CAPTCHA. I think that's how we know it works.

Q: Hi Luis,
I was wondering about your CAPTCHA project to transcribe old texts. If a computer cannot read distorted words, how does it know if you entered the correct answer? Say my eyesight is bad, and I type one letter wrong. Will the computer catch the error? Anonymous

von Ahn: It gives the same word to multiple users. If you make a mistake, odds are other people won't make the exact same mistake.

Q: As a variation for CAPTCHA, would it be possible to have an image presented to the viewer and ask that person what the image is? For example, a picture of a skateboard off in the distance. Would that function as well? Kelly Banco, Edmonton, Alberta, Canada

von Ahn: Yep, we've explored this idea quite a bit. It's a good idea. :) [Editor's note: For more about the image labeling projects, see the interview Games With A Purpose].

Q: When do you think that computer chips will be directly implanted into the brain, so that we don't have to carry our iPods or worry about data files? Anonymous

von Ahn: I wish it were tomorrow!

Related Links

  • Profile: Luis von Ahn

    A computer scientist finds novel ways to stop spammers and harness the brainpower of millions of people.

  • Hear From Luis von Ahn

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