In a nutshell, this is how Prolific is different from MTurk and other crowdsourcing platforms:
You can specify various prescreening filters prior to launching your study (e.g., nationality, first language, ethnicity, political affiliation, socio-economic status, etc.), so participants don't get screened out while talking part. You can also recruit a custom sample.
You can get unique participants each time (i.e., you can easily exclude people who have previously taken part) and you can filter by number of studies completed. Plus, we have algorithms in place to fairly allocate study spaces, which means that our pool doesn't suffer as much from non-naïveté (Chandler et al., 2015).
We offer an international participant pool (MTurk nowadays only offers US Americans) and we're very transparent about the composition of our pool.
We have many mechanisms in place to ensure a high quality of our pool. If you want to learn more, feel free to check out our blog post on the topic.
Ethical research practices
We protect and value our participant pool and enforce minimum payments that are consistent with research ethic’s guidelines, which means you have access to a large, motivated and diverse participant pool.
While offering all of the above, we're very low-cost as compared to other services. We charge 33.33% commission whereas MTurk charges up to 40%.
In addition, there are some further important aspects to consider:
Participation of minors is prohibited
Our Terms and Conditions explicitly state that participants have to be at least 18 years old to take part in studies on Prolific.
Participants are not employees of Prolific
We do not consider our participants as our employees in any way; they simply volunteer for research projects and earn rewards, which is covered by UK tax law. To make sure that our participants don't turn into professional survey takers, we have a rate-limiting mechanism in place that distributes studies as evenly as possible across the entire participant pool.