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Cute Kittie Captcha

Microsoft Research has developed Asirra, a CAPTCHA system that uses something far more reliable than scrambled letters: Pets! The system presents the user with twelve random photos of cats and dogs pulled from’s database and asks the user to click on the cats, and only the cats. The idea is that only a human, but not a bot, could successfully identify the cats.

It’s a great idea, and easier to understand than some CAPTCHAs (some of which are just awful), but it suffers from a simple problem: You can’t always tell if a cat is not a dog. Some cats, particularly dark ones, are hard to distinguish from dogs, and I even found one photo that had a cat sitting next to a dog! Still, even though I failed twice and my wife failed once, it seems almost impossible that a computer would ever pass it, except through random chance.

You can use Asirra on your website, and Microsoft gives the full instructions. And if you were wondering, Asirra stands for:

Animal Species Image Recognition for Restricting Access

(via the Virtual Earth blog)

March 23rd, 2007 Posted by Nathan Weinberg | Humor | 4 comments

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  1. Well, this system seems to give more chances for a computer to correctly guess than the scrambled letters.

    Comment by Pharod | March 23, 2007

  2. “It’s a great idea, and easier to understand than some CAPTCHAs (some of which are just awful)”

    Agree 100%. Some I stare at for a 1/2 a minute or have to try 2-3 times because it’s so unclear wtf they’re actually showing.

    Comment by Bob | March 23, 2007

  3. Too bad it isn’t accesibility friendly, Nathan :( The sight-impaired have no chance with this one. Although it would be a cool hack if by clicking a sound file different animal sounds could be heard.

    Comment by TDavid | March 23, 2007

  4. Tdavid, more and more captchas these days are more accessible to the blind than they are to everybody else! So many times, I just want to click that audio button because I can’t read a damn letter in the regular captcha. We need to concentrate on fixing or junking the current system before we can make sure the much smaller percentage of blind web users are accomodated.

    Comment by Nathan Weinberg | March 25, 2007

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