This tutorial details how to take an online experiment that you have previously used Amazon Mechanical Turk (AMT) to recruit participants and switch over to using Prolific for participant recruitment instead.
After logging in to Prolific, click "new study":
Fill in all the study details. After doing so, under "Study Link", paste the URL of your study and select the option "I'll use URL parameters":
Under "Study Completion" use the option "I'll redirect them using a URL":
Fill in the other sections ("Audience", "Study Cost") as needed.
Both AMT and Prolific fetch a similar set of variables from a URL query, and so collecting Prolific parameters, such as participant-level identifiers, will seem very familiar.
Here is a table with the exact URL substrings that the query should find, as well as their equivalents on AMT:
| URL Query Parts | AMT | Prolific |
|---|---|---|
| Participant-level identifier | workerId | PROLIFIC_PID |
| Study-level identifier | hitId | STUDY_ID |
| Session-level identifier | assignmentId | SESSION_ID |
| Where to submit* | turkSubmitTo | (doesn’t exist) |
*This one is unique to AMT, and it always refers to the top-level domain, “https://www.mturk.com”
We can harvest these URL parameters via client-side javascript as follows:
// get experiment ID information from URL
var queryString = window.location.search;
var urlParams = new URLSearchParams(queryString);
var prolificID = urlParams.get('PROLIFIC_PID'); // ID unique to the participant
var studyID = urlParams.get('STUDY_ID'); // ID unique to the study
var sessionID = urlParams.get('SESSION_ID'); // ID unique to the particular submission
After successfully harvesting the URL parameters, you can then save it to your database as part of the trial information.
Upon completion of the study, the participant must be directed to the URL specified under the "Study Completion" section of Prolific. The preferred way is to use a button at the end of the experiment, which, when clicked, redirects the participant to the completion URL. A line of code that does this is:
window.open("https://app.prolific.co/submissions/complete?cc=XXXXXXX","_self")
In the above line, the 'XXXXXXX' within the completion URL will be an alpha-numeric string that functions as the Completion Code for Prolific workers. You will have to manually copy this URL from Prolific's interface, and paste it into this line of your experiment code.
All that's left is to publish the study! After successful completion of the study, the participant's prolificID will automatically appear on the Prolific website in the "Active" tab, under the specified study name:
Bonusing on Prolific will require you to access the bonus scores as recorded in your databse (from the participant data stored during the experiments), to create a csv file mapping the Prolific PROLIFIC_PID to the relevant bonus. That csv is then uploaded manually onto Prolific’s user interface to bulk-bonus participants with their respective bonus money. This task has not yet been automated, but once it is, an explanation and sample code will be uploaded to this article.
