Chris Higgins
How Electronic “20 Questions” Games Work
by Chris Higgins - July 17, 2009 - 12:25 PM

This article was originally published in March of 2008.

20Q GameIt was about five years ago when I first saw a 20Q ball. The tiny handheld device scrolled text across its meager one-line screen, inviting me to challenge it in a game of 20 Questions. I immediately thought of an object I figured it wouldn’t guess (“iPod”) and began to play the game. After a series of slightly odd questions — including “Does it bring joy to people?” — the little ball gave its guess: “MP3 player.” Wow. It was right.

So how does this 20Q device work? The short answer is “artificial intelligence.” The long answer involves lots of practice. In 1988, Canadian inventor Robin Burgener programmed a neural network (a specialized form of computer program) capable of playing 20 Questions, but without a library of knowledge about common objects. He proceeded to teach it twenty questions about the object “cat,” then handed the program (on floppy disk) to friends and encouraged them to play, recording their play sessions as it went. For 20Q, playing equals learning, as it develops “synaptic connections” whenever it receives answers to questions. It’s able to reinforce connections by playing games over and over with different people, gradually learning which answers are correct and which aren’t. (Thus it’s difficult to “poison” the system by purposely giving it wrong answers.) The program can then use these connections to pose clarifying questions, eventually arriving at an answer.

By 1995, Burgener had a good body of connections in his neural network. He put a version of the 20Q program on the web and encouraged web visitors to play with it (thus training it in the process). After the online version of 20Q had played one million games (amassing 10 million synaptic connections in the process), Burgener boiled down the 20Q system into a simplified 20Q-on-a-chip version. The hardware version was incapable of learning, but contained information about the 2,000 most popular objects chosen by users of the online program. As such, it embodied a shocking “intelligence” that toy makers later put into the 20Q balls, now available at toy stores everywhere for under $15. (Specialized versions are also available, including a Harry Potter unit, and later versions of the handheld game have more information built-in.)

Today (or at least as of late 2006, the last time its online FAQ seems to have been updated), the online version of 20Q guesses correctly about 80% of the time, and if you allow it 25 questions, it claims a 98% success rate. With over 60 million games played online, the neural net continues to learn — and this learning can be translated into future versions of the 20Q handheld games. In an interview with Kevin Kelly, Burgener said, “It is learning, but it is not increasing its success rate. What happens is that it is learning to play more kinds of people, people who don’t speak English easily, or who have never played 20 questions, or who come from different cultures, and to understand more difficult kinds of things.”

You can play 20Q Online for free, or pick up a handheld version at any reputable toy or game store. You can read a bit more about the game at Wikipedia or check out more on neural networks for a deeper understanding.

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Comments (13)

  1. When ever I play with these things, I always try to get it to guess itself – in the hopes that it’ll become self aware! :) The best it does it answer “game” … I guess they programed it such that it’ll never be specific enough to guess itself and then start asking YOU questions.

    “Where am I?” “What is my purpose?” :P

    posted by Steve on 7-17-2009 at 12:53 pm

  2. Robin Burgener’s concept was hardly original. Back in the mid 1970′s, Arthur Luehrmann wrote a program at Dartmouth College (later modified and shortened by DEC’s Nathan Teichholtz and Creative Computing Magazine’s Steve North) involving exactly the same concept – that of having a computer program learn new concepts (originally limited to just new animals) and play the game better as it went.

    You can see the original program write-up online at:
    http://www.atariarchives.org/basicgames/showpage.php?page=4
    http://www.atariarchives.org/basicgames/showpage.php?page=5

    posted by gmsc on 7-17-2009 at 2:21 pm

  3. Steve, that’s hilarious. Wish I had thought of that. :)

    posted by Jen on 7-17-2009 at 2:47 pm

  4. The first time I picked one of these up, I figured it would never guess my object. However, 20 questions later came the guess: Siberian Tiger. It was right! I promptly put the thing down and walked away, it was creepy.

    posted by Kat on 7-17-2009 at 3:06 pm

  5. “Today (or at least as of late 2006″
    This post has been dug out from something that was written close to 3 years ago!! & I read it all….. I must have way too much free time on my hands..

    posted by Amit on 7-17-2009 at 4:55 pm

  6. The first time I came across this game online, I picked a crochet hook. It got as close as “knitting needle”, but still wrong. Just played it now, and it *still* doesn’t know what a crochet hook is. Nor has it figured out the existence of breastmilk yet. (Both of these are after 30 questions/guesses, by the way, & I answered the questions to the best of my ability.)

    posted by Sabra on 7-17-2009 at 5:32 pm

  7. The problem with these neural net builders is the new questions always get added to the leaves and the number of questions it takes to get an answer gets higher and higher. It can’t add a good third question because it would have to ask that question about hundreds of items already in the net.

    posted by Steve M on 7-17-2009 at 5:59 pm

  8. It didn’t get “shoe horn”, but it got dental floss and CD.

    posted by PJ on 7-17-2009 at 9:21 pm

  9. These things creep me out. I’m going to stick with a nice game of chess.

    posted by Kristin on 7-18-2009 at 2:43 am

  10. I’m sorry, but I still think it’s magic. This little toy blows my mind on a regular basis.

    posted by Kelli on 7-18-2009 at 11:14 am

  11. This reminds me of a website I’ve enjoyed in the past called “Guess the Dictator/Sitcom Character.” Click on my name to go to the site.

    posted by Jaclyn McKewan on 7-18-2009 at 7:19 pm

  12. @Amit – this article was written in 2008, as stated at the beginning. When I cited a source that was dated (a FAQ article dated 2006), I simply included the date for that info, as the info was already a few years old when the article was written.

    posted by Chris Higgins on 7-19-2009 at 11:41 pm

  13. Man the 20 question website is addicting… Of all the catergories movies is the best one.

    Another awesome way to procrastinate at work.

    posted by Chrystani on 7-21-2009 at 4:28 pm

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