Phetch is a

game with a purpose A human-based computation game or game with a purpose (GWAP) is a human-based computation technique of outsourcing steps within a computational process to humans in an entertaining way (gamification). Luis von Ahn first proposed the idea of "hum ...

intended to label images on the internet with descriptive captions suitable to assist sight impaired readers. Approximately 75% of the images on the web do not have proper

ALT text The alt attribute is the HTML attribute used in HTML and XHTML documents to specify alternative text (alt text) that is to be displayed in place of an element that cannot be rendered. The alt attribute is used for short descriptions, with lon ...

labels, making them inaccessible through

screen readers A screen reader is a form of assistive technology (AT) that renders text and image content as speech or braille output. Screen readers are essential to people who are blind, and are useful to people who are visually impaired, illiterate, or hav ...

. The solution aimed at by Phetch is to label the images external to the web page rather than depending upon the web page author to create proper alt text for each image. Rather than paying people to do the mundane task of labeling images, Phetch aims to create a fun game that produces such descriptions as a side effect of having fun. Phetch was created by

Luis von Ahn Luis von Ahn (; born 19 August 1978) is a German-Guatemalan entrepreneur and a consulting professor in the Computer Science Department at Carnegie Mellon University in Pittsburgh, Pennsylvania. He is known as one of the pioneers of crowdsourcin ...

and Shiry Ginosar of

Carnegie Mellon University Carnegie Mellon University (CMU) is a private research university in Pittsburgh, Pennsylvania. One of its predecessors was established in 1900 by Andrew Carnegie as the Carnegie Technical Schools; it became the Carnegie Institute of Technology ...

following the pattern set by the earlier

ESP game The ESP game is a human-based computation game developed to address the problem of creating difficult metadata. The idea behind the game is to use the computational power of humans to perform a task that computers cannot (originally, image recog ...

. Phetch is played by three to five people. One is designated as a describer, while the rest are seekers. The describer is shown an image, which he describes to the seekers. The seekers use an Internet image search engine to attempt to find the image being described. The first seeker to find the image gains points and becomes the describer for the next round. The describer is also rewarded for a successful outcome. The data produced as the side effect of playing the game is the describer's descriptions of the image. An imagined system for serving these descriptions from a centralized server is described in the Phetch paper. The output of the game was later used to improve image search engines and the game itself was later proposed as a mechanism to test interactive search interfaces.Ginosar, Shiry:
Human Computation for HCIR Evaluation
, Proceedings, HCIR 2007, pp. 40-42. In late 2008, public access to Phetch was discontinued when the

was moved to the gwap.com domain. Peekaboom was also discontinued in late 2008.

Notes

{{reflist Guessing games Human-based computation games