Prolific is a crowd-sourcing platform for running studies. In contrast to the widely-used Mechanical Turk, it’s specific to studies, has a much better interface, pricing that’s fair to participants, and useful filters to find the right people for your study.
Amazon's Mechanical Turk is used for many empirical studies published in the visualization literature, but every time I’ve used it I’ve been just amazed at how ugly and poorly designed it is. It’s also annoying to have to split up your study into nine-participant chunks to avoid the 20% “tax” you pay from the tenth participant in the same HIT.
Prolific is much simpler and cleaner. The service is specific to running studies, which means you get more motivated participants. They can also expect to be paid more fairly, since Prolific’s pricing is based on a reasonable minimum wage, which again helps motivation and data quality. This can make studies there look more expensive, but it includes their fees and a fair wage.
It’s really easiest if you just sign up and check it out yourself. If you’re not convinced, see some of the responses to my tweet about Prolific during VIS, including from people who participate in studies.
Mechanical Turk may be a good general platform for crowdsourcing, but for running studies, Prolific is far superior.