Payment for optional follow up study?

My study consists of two parts.
In the first part participants work alone (duration 10 minutes), in the second part together in a group of 3 (duration 30 minutes). Part 2 only works if part 1 has been done before, but part 1 can be done alone for my research purposes.

The problem with group studies is that participants leave and prevent the group from working or that there are not enough participants to fill a group. Therefore, I would like to design my study in such a way that the second part - the group work - is optional. If a participant cannot continue working, they are brought to the last page of the study to complete it. If participants complete the second part, they get more money.

I am now wondering how to set up the payment. My idea is to set the time and reward based on the first part and pay the second part as a bonus. Of course, I also wonder whether Prolific includes the bonus when it comes to the fairness of participant payment. Of course, I would make it clear in the description how the payment works.

How can we work on it am interested

Dear Donald
I think that you should ask about working on Prolific here

because this is the forum for those that pay.

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Dear Jkpb

Welcome to the forum. I am sorry that I missed your post. The FAQ for longitudinal studies is here.

Prolific prefers that we set up each study separately as a separate Prolific study so that, as you have guessed, they can keep an eye on fairness of payment, rather than paying by bonuses. There is one exception to this in diary studies afaik. Ordinarily for your study you’d invite those that completed the first study back for a second one using the custom allowlist, and messaging, or an allowlist based upon participation on Prolific and having completed the first study. The problem is groups not filling up and also participants not coming back.


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An alternative it to set your study up in Gorilla which allows you to create more complex flows for participants. And you can mix and match surveys, tasks, games, multiplayer tasks and more …

In your case, all participants (from Prolific) would do Part 1, and then they’d have the option to exit or continue to Part 2 - the multiplayer part. And set up a bonus payment for the latter group.

Multiplayer tasks are supported in Gorilla and we have a lobby where participants can gather until there are enough to continue.

Happy to chat if that would be useful; we work very closely with Prolific.

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