ESP Game

The ESP Game is an experiment in human computation originally conceived by Luis von Ahn of Carnegie Mellon University. The idea behind the game is to use the computational power of humans to perform a task that computers cannot yet do (in this case, labeling images) by packaging the task as a game. Some players believe that there is no real human partner, and that the partner's guesses are provided by the software to give the illusion of a competitive game. This is, however, a horrible misconception. A simple test, having two people simultaneously sign up and monitor their image, will show that there are, indeed, real human partners.

Rules of the game
Once logged in, a user is automatically matched with a random partner. The partners do not know each other's identity and they cannot communicate. Once matched, they will both be shown the same image. Their task is to agree on a word that would be an appropriate label for the image. They both enter possible words, and once a word is entered by both partners (not necessarily at the same time), that word is agreed upon, and that word becomes a label for the image. Once they agree on a word, they are shown another image. They have two and a half minutes to label 15 images.

Both partners have the option to pass; that is, give up on an image. Once one partner passes, the other partner is shown a message that their partner wishes to pass. Both partners must pass for a new image to be shown.

Some images have "taboo" words; that is, words that cannot be entered as possible labels. This is done automatically by the system: once an image has been labeled enough times with the same word, that word becomes taboo so that the image will get a variety of different words as labels.

Accuracy
The idea of partnering two people to label images ensures that entered words will be accurate. Since the only thing the two partners have in common is that they both see the same image, they must enter reasonable labels to have any chance of agreeing on one.

Idea
Image recognition is currently a task that computers are incapable of. Humans are perfectly capable of it, but not necessarily willing. The ESP Game makes humans willing to perform this task by making a game out of it. Some users reportedly play over 40 hours a week. According to the game's creator, if the ESP Game gains popularity comparable to other online games, all images on Google Images could be labeled using the Google Image Labeler game in just a few months.

The applications and uses of having so many labeled images are significant; for example, more accurate image searching and accessibility for visually-impaired users (by reading out an image's labels).