I realized that unfortunately the current illustration on the CAPTCHA page does not make sense.

illustration on the CAPTCHA page

I think that this is supposed to illustrate the Turing test, but the illustration misses the point because the examiner can see the subject physically in this picture. The point of the Turing test is that the examiner and the subject are kept in separate rooms so that the examiner has to distinguish a human from a computer by interacting with the subject only through a communication channel that is equally available to both a human and a computer.

I added a separator between the examiner and the two subjects claiming to be human. This may not be sufficient, but I hope that it is better than the current picture:

example of modified illustration

  • $\begingroup$ I was not sure if this should be tagged as [feature-request] or [bug], but “bug” sounded too strong a word for this, so I decided to go with [feature-request]. $\endgroup$ Commented Dec 10, 2010 at 19:30
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    $\begingroup$ One might say that it is the cstheory web server, which is a computer, that is doing the job of distinguishing humans from computers. $\endgroup$ Commented Dec 11, 2010 at 4:26
  • $\begingroup$ I agree with Robin: in the Turing Test the examiner is a human, while in our case it's a computer. I think we should change the picture accordingly. $\endgroup$ Commented Dec 11, 2010 at 8:01
  • $\begingroup$ @Robin: That makes sense. As Walter says, it might be better to change the picture to that. I do not know if it is understandable, though. Anyway I do not mean to improve the picture by myself. I posted the “modified” picture only to clarify my point. $\endgroup$ Commented Dec 11, 2010 at 14:02

1 Answer 1


I realized that math.stackexchange.com uses a cartoon from xkcd. I think that it has a wit and is better than an illustration which just explains what the Turing test is (even with any of the proposed corrections). Please consider using it.

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    $\begingroup$ Much better, if we can get a permission to use it. $\endgroup$ Commented Dec 12, 2010 at 17:45
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    $\begingroup$ It's licensed under creative commons (see the bottom of the page). $\endgroup$ Commented Dec 12, 2010 at 22:25

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