Analyzing the Amazon Mechanical Turk Marketplace

Dec 2010

Authors: Panagiotis G. Ipeirotis

Venue: ACM XRDS (Crossroads), Vol. 17, No 2, Winter 2010


Amazon Mechanical Turk (AMT) is a popular crowdsourcing marketplace, introduced by Amazon in 2005. The marketplace is named after an 18th century “automatic” chess-playing machine, which was handily beating humans in chess games. Of course, the robot was not using any artificial intelligence algorithms back then. The secret of the Mechanical Turk machine was a human operator, hidden inside the machine, who was the real intelligence source. AMT is also a marketplace for small tasks that cannot be easily automated. For example, humans can tell if two different descriptions correspond to the same product, can easily tag an image with descriptions of its content, or can easily transcribe with high quality an audio snippet-though all those tasks are extremely difficult for computers to do. Using Mechanical Turk, computers can use a programmable API to post tasks on the marketplace, which are then fulfilled by human users. This API-based interaction gives the impression that the task can be automatically fulfilled, hence the name. In the marketplace, employers are known as requesters and they post tasks, called human intelligence tasks, or HITs. The HITs are then picked up by online users, referred to as workers, who complete them in exchange for a small payment, typically a few cents per HIT. Since the concept of crowdsourcing is relatively new, many potential participants have questions about the AMT marketplace. For example, a common set of questions that pop up in an “introduction to crowdsourcing and AMT” session are the following:
• Who are the workers that complete these tasks?
• What type of tasks can be completed in the marketplace?
• How much does it cost?
• How fast can I get results back?
• How big is the AMT marketplace?