Imagine a task that is simple for a human and difficult for a computer. For example, recognizing if a photograph contains a cat or a dog is a straightforward task even for a few months old child (Quinn & Eimas, 1996), but extremely difficult, if not impossible, for a computer (Shotton et al., 2006) because the two are quite similar in terms of shape. In order to capitalize on human’s superiority over computers in some kind of tasks, Amazon.com, Inc. (NASDAQ: AMZN) came up with a platform called Amazon Mechanical Turk (https://www.mturk.com/mturk/welcome), where it is possible to ask human workers to complete HITs – Human Intelligence Tasks.