Crowdsourcing as self-fulfilling prophecy: Influence of discarding workers in subjective assessment tasks

Crowdsourcing has established itself as a powerful tool for multimedia researchers, and is commonly used to collect human input for various purposes. It is also a fairly widespread practice to control the contributions of users based on the quality of their input. This paper points to the fact that applying this practice in subjective assessment tasks may lead to an undesired, negative outcome. We present a crowdsourcing experiment and a discussion of the ways in which control in crowdsourcing studies can lead to a phenomenon akin to a self-fulfilling prophecy. This paper is intended to trigger discussion and lead to more deeply reflective crowdsourcing practices in the multimedia context.