
A reCAPTCHA is more than a CAPTCHA, it also helps to digitize old books. - amichail
http://bmaurer.blogspot.com/2007/05/recaptcha-new-way-to-fight-spam.html
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nickb
Just a quick warning regarding this service. After playing with this, I've
noticed that about 20% of the words that were displayed were completely
unreadable. If you're a startup that doesn't want to lose any potential users,
I'd advise against using this service. If you're an established company that
is getting hammered with spam, well, maybe you can afford to use this.

~~~
vlad
The ones that are unreadable are likely the words from the texts. Those words
do not count against you. You only have to get the real captcha correctly,
which happens to be the clearest word. Try experimenting by entering just one
of the words.

I had no difficulty with these, while I usually have a LOT of difficulty
searching vBulletin forums I am not a member of.

I would write "If you're having difficulty, enter one of these words" at the
top. The user will likely enter the clearest.

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amichail
IMO, human computation is a field with enormous potential. But strangely,
there are few publications on the topic. It's not taken seriously in computer
science yet.

Or maybe it requires a different sort of thinking than what most computer
scientists are accustomed to?

Or perhaps most computer scientists feel that human computation is cheating?
For them, maybe there is no reward in this sort of research. They are more
interested in something technically difficult, even if the results are much
worse.

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amichail
BTW, in terms of cleverness in human computation, <http://listengame.org> is a
must-see.

You can use the approach behind listengame.org to build a service that gives
first impressions on all sorts of things.

In fact, you can apply the listengame.org approach to online advertising to
encourage people to look at online ads very carefully. Moreover, advertisers
would get feedback on their ads.

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spiralhead
who's to say the user will not enter an incorrect word or mis-type? To get
reasonably accurate results, you would have to take a handful of samples for
each word and take the one with the highest frequency. And even then, users
will figure out that they really only need to enter one word and random crap
for the other one (it will always look different). Not a bad notion but too
much room for error and randomness to be reliable.

~~~
amichail
How do you know it will always look different? Maybe the look could be faked
reasonably well so that both words would look similar.

~~~
spiralhead
_Maybe is the key word there. It would be challenging since you would have to
apply some sort of noise filter to each of the fakes to simulate a scanned
image. You would also have to consider fonts

