where you've been asked to read

a distorted sequence of characters like this?

How many of you found it really annoying?

(Laughter)

OK, outstanding. So I invented that.

(Laughter)

Or I was one of the people who did it.

That thing is called a CAPTCHA.

And it is there to make sure you, the entity filling out the form,

are a human and not a computer program

that was written to submit the form millions of times.

The reason it works is because humans, at least non-visually-impaired humans,

have no trouble reading these distorted characters,

whereas programs can't do it as well yet.

In the case of Ticketmaster,

the reason you have to type these characters

is to prevent scalpers from writing a program

that can buy millions of tickets, two at a time.

CAPTCHAs are used all over the Internet.

And since they're used so often,

a lot of times the sequence of random characters shown to the user

is not so fortunate.

So this is an example from the Yahoo registration page.

The random characters that happened to be shown to the user

were W, A, I, T, which, of course, spell a word.

But the best part is the message

that the Yahoo help desk got about 20 minutes later.

[Help! I've been waiting for over 20 minutes and nothing happens.]

(Laughter)

This person thought they needed to wait.

This, of course, is not as bad as this poor person.

(Laughter)

CAPTCHA Project is something that we did at Carnegie Melllon over 10 years ago,

and it's been used everywhere.

Let me now tell you about a project that we did a few years later,

which is sort of the next evolution of CAPTCHA.

This is a project that we call reCAPTCHA,

which is something that we started here at Carnegie Mellon,

then we turned it into a start-up company.

And then about a year and a half ago, Google actually acquired this company.

Let me tell you what this project started.

This project started from the following realization:

It turns out that approximately 200 million CAPTCHAs

are typed everyday by people around the world.

When I first heard this, I was quite proud of myself.

I thought, look at the impact my research has had.

But then I started feeling bad.

Here's the thing: each time you type a CAPTCHA,

essentially, you waste 10 seconds of your time.

And if you multiply that by 200 million,

you get that humanity is wasting about 500,000 hours every day

typing these annoying CAPTCHAs.

(Laughter)

So then I started feeling bad.

(Laughter)

And then I started thinking, of course, we can't just get rid of CAPTCHAs,

because the security of the web depends on them.

But then I started thinking, can we use this effort

for something that is good for humanity?

So see, here's the thing.

While you're typing a CAPTCHA, during those 10 seconds,

your brain is doing something amazing.

Your brain is doing something that computers cannot yet do.

So can we get you to do useful work for those 10 seconds?

Is there some humongous problem that we cannot yet get computers to solve,

yet we can split into tiny 10-second chunks

such that each time somebody solves a CAPTCHA,

they solve a little bit of this problem?

And the answer to that is "yes," and this is what we're doing now.

Nowadays, while you're typing a CAPTCHA,

not only are you authenticating yourself as a human,

but in addition you're helping us to digitize books.

Let me explain how this works.

There's a lot of projects trying to digitize books.

Google has one. The Internet Archive has one.

Amazon, with the Kindle, is trying to digitize books.

Basically, the way this works is you start with an old book.

You've seen those things, right?

Like a book?

(Laughter)

So you start with a book and then you scan it.

Now, scanning a book

is like taking a digital photograph of every page.

It gives you an image for every page.

This is an image with text for every page of the book.

The next step in the process is that the computer needs to be able

to decipher the words in this image.

That's using a technology called OCR, for optical character recognition,

which takes a picture of text

and tries to figure out what text is in there.

Now, the problem is that OCR is not perfect.

Especially for older books

where the ink has faded and the pages have turned yellow,

OCR cannot recognize a lot of the words.

For things that were written more than 50 years ago,

the computer cannot recognize about 30 percent of the words.

So now we're taking all of the words that the computer cannot recognize

and we're getting people to read them for us

while they're typing a CAPTCHA on the Internet.

So the next time you type a CAPTCHA, these words that you're typing

are actually words from books that are being digitized

that the computer could not recognize.

The reason we have two words nowadays instead of one

is because one of the words

is a word that the system just got out of a book,

it didn't know what it was and it's going to present it to you.

But since it doesn't know the answer, it cannot grade it.

So we give you another word,

for which the system does know the answer.

We don't tell you which one's which and we say, please type both.

And if you type the correct word

for the one for which the system knows the answer,

it assumes you are human

and it also gets some confidence that you typed the other word correctly.

And if we repeat this process to 10 different people

and they agree on what the new word is,

then we get one more word digitized accurately.

So this is how the system works.

And since we released it about three or four years ago,

a lot of websites have started switching from the old CAPTCHA,

where people wasted their time,

to the new CAPTCHA where people are helping to digitize books.

So every time you buy tickets on Ticketmaster,

you help to digitize a book.

Facebook: Every time you add a friend or poke somebody,

you help to digitize a book.

Twitter and about 350,000 other sites are all using reCAPTCHA.

And the number of sites that are using reCAPTCHA is so high

that the number of words we're digitizing per day is really large.

It's about 100 million a day,

which is the equivalent of about two and a half million books a year.

And this is all being done one word at a time

by just people typing CAPTCHAs on the Internet.

(Applause)

Now, of course,

since we're doing so many words per day,

funny things can happen.

This is especially true because now we're giving people

two randomly chosen English words next to each other.

So funny things can happen.

For example, we presented this word.

It's the word "Christians"; there's nothing wrong with it.

But if you present it along with another randomly chosen word,

bad things can happen.

So we get this.

[bad Christians]

But it's even worse, because the website where we showed this

actually happened to be called The Embassy of the Kingdom of God.

(Laughter)

Oops.

(Laughter)

Here's another really bad one.

JohnEdwards.com

[Damn liberal]

(Laughter)

So we keep on insulting people left and right everyday.

Of course, we're not just insulting people.

Here's the thing. Since we're presenting two randomly chosen words,

interesting things can happen.

So this actually has given rise to a really big Internet meme

that tens of thousands of people have participated in,

which is called CAPTCHA art.

I'm sure some of you have heard about it.

Here's how it works.

Imagine you're using the Internet and you see a CAPTCHA

that you think is somewhat peculiar,

like this CAPTCHA.

[invisible toaster]

What you're supposed to do is you take a screenshot of it.

Then of course, you fill out the CAPTCHA because you help us digitize a book.

But first you take a screenshot

and then you draw something that is related to it.

(Laughter)

That's how it works.

(Laughter)

There are tens of thousands of these.

Some of them are very cute.

[clenched it]

(Laughter)

Some of them are funnier.

[stoned Founders]

(Laughter)

And some of them, like paleontological shvisle ...

(Laughter)

they contain Snoop Dogg.

(Laughter)

OK, so this is my favorite number of reCAPTCHA.

So this is the favorite thing that I like about this whole project.

This is the number of distinct people

that have helped us digitize at least one word out of a book through reCAPTCHA:

750 million, a little over 10 percent of the world's population,

has helped us digitize human knowledge.

And it is numbers like these that motivate my research agenda.

So the question that motivates my research is the following:

If you look at humanity's large-scale achievements,

these really big things

that humanity has gotten together and done historically --

like, for example, building the pyramids of Egypt

or the Panama Canal

or putting a man on the Moon --

there is a curious fact about them,

and it is that they were all done with about the same number of people.

It's weird; they were all done with about 100,000 people.

And the reason for that is because, before the Internet,

coordinating more than 100,000 people,

let alone paying them, was essentially impossible.

But now with the Internet, I've just shown you a project

where we've gotten 750 million people to help us digitize human knowledge.

So the question that motivates my research is,

if we can put a man on the Moon with 100,000,

what can we do with 100 million?

So based on this question,

we've had a lot of different projects that we've been working on.

Let me tell you about one that I'm most excited about.

This is something that we've been semiquietly working on

for the last year and a half or so.

It hasn't yet been launched. It's called Duolingo.

Since it hasn't been launched, shhh!

(Laughter)

Yeah, I can trust you'll do that.

So this is the project. Here's how it started.

It started with me posing a question to my graduate student, Severin Hacker.

OK, that's Severin Hacker.

So I posed the question to my graduate student.

By the way, you did hear me correctly; his last name is Hacker.

(Laughter)

So I posed this question to him: How can we get 100 million people

translating the web into every major language for free?

There's a lot of things to say about this question.

First of all, translating the web.

Right now, the web is partitioned into multiple languages.

A large fraction of it is in English.

If you don't know English, you can't access it.

But there's large fractions in other different languages,

and if you don't know them, you can't access it.

So I would like to translate all of the web,

or at least most of it, into every major language.

That's what I would like to do.

Now, some of you may say, why can't we use computers to translate?