human computation csc4170 web intelligence and social computing tutorial 7 tutor: tom chao zhou...

Human Computation

CSC4170 Web Intelligence and Social ComputingTutorial 7

Tutor: Tom Chao ZhouEmail: [email protected]

Outline

Definition & Early Work Human Computation:

Case Study: reCAPTCHA Game with a purpose:

Case Study: ESP Game Q&A Reference

Definition & Early Work

Human-based Computation: Human-based Computation is a computer science technique in

which a computational process performs its function by outsourcing certain steps to humans.

This approach leverages differences in abilities and alternative costs between humans and computer agents to achieve symbiotic human-computer interaction.

Definition & Early Work

Early Work: Interactive evolutionary computation. The idea is proposed by Richard Dawkins (http://en.wikipedia.or

g/wiki/Richard_Dawkins). The preference of a human experimenter is used to guide the ev

olution of two-dimensional sets of line segments. This program asks a human to be the fitness function of an evolu

tionary algorithm, so that the algorithm can use human visual perception and aesthetic judgment to do something that a normal evolutionary algorithm cannot do.

Human Computation Case Study: reCAPTCHA

What is CAPTCHA? A CAPTCHA (completely automated public Turing test to tell

computers and humans apart) is a program that can tell whether its user is a human or a computer.

Colorful images with distorted text at the bottom of Web registration forms

What is CAPTCHA? A CAPTCHA (completely automated public Turing test to tell

computers and humans apart) is a program that can tell whether its user is a human or a computer.

Colorful images with distorted text at the bottom of Web registration forms


What is CAPTCHA? It was coined in 2000 by Luis von Ahn, Manuel Blum, Nicholas H

opper and John Langford of Carnegie Mellon University. Applications of CAPTCHA:

Preventing Comment Spam in Blogs. Protecting Website Registration. Online Polls. Preventing Dictionary Attacks. CAPTCHAs can also be used to prev

ent dictionary attacks in password systems. Search Engine Bots. Preventing search engine bots to crawl the pag

es.


Statistics about CAPTCHA and some thought. About 200 million CAPTCHAs are solved by humans around the

world every day. In each case, roughly ten seconds of human time are being spen

t. Individually, that's not a lot of time, but in aggregate these little p

uzzles consume more than 150,000 hours of work each day. What if we could make positive use of this human effort?


What is reCAPTCHA? reCAPTCHA does exactly that by channeling the effort spent sol

ving CAPTCHAs online into "reading" books. reCAPTCHA is a free CAPTCHA service that helps to digitize bo

oks, newspapers and old time radio shows.


What is reCAPTCHA? The old books are being photographically scanned, and then tra

nsformed into text using "Optical Character Recognition" (OCR). However, OCR produces images, which cannot be searched. reCAPTCHA improves the process of digitizing books by sendin

g words that cannot be read by computers to the Web in the form of CAPTCHAs for humans to decipher.


Ideas of reCAPTCHA: Each new word that cannot be read correctly by OCR is given to

a user in conjunction with another word for which the answer is already known.

The user is then asked to read both words. If they solve the one for which the answer is known, the system assumes their answer is correct for the new one.

The system then gives the new image to a number of other people to determine, with higher confidence, whether the original answer was correct.


Performances of reCAPTCHA: reCAPTCHA is able to achieve over 99.5% transcription accurac

y at the word level.

Game with a purpose (GWAP) Case Study: ESP Game

GWAP: A game with a purpose (GWAP) is a game played on a compute

r that serves some purpose for the people setting up the game by harnessing human abilities in an entertaining setting.

There are many activities that are almost trivial for humans to perform that have stymied computers, e.g., labelling image.


ESP Game: An effort in human computation originally conceived by Luis Von

Ahn of CMU to label images. Two players attempt to assign the same labels to an image. The game records the results of matches as image labels and th

e players enjoy the encounter because of the competitive and timed nature of it.

To ensure that people do their best to accurately label the images, the game requires two people who have only the image in common, to choose the same word as an image label.


ESP Game:


ESP Game: Demo: http://www.gwap.com/gwap/gamesPreview/espgame/ Play as a guest.

Questions?

Reference

reCAPTCHA: http://recaptcha.net/ http://www.cs.cmu.edu/~biglou/captcha_cacm.pdf http://www.cs.cmu.edu/~biglou/captcha_crypt.pdf http://recaptcha.net/reCAPTCHA_Science.pdf

ESP Game: http://www.gwap.com/gwap/gamesPreview/espgame/

Homepage of Luis Von Ahn http://www.cs.cmu.edu/~biglou/

human computation csc4170 web intelligence and social computing tutorial 7 tutor: tom chao zhou...

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