Just like payment, extra credit remuneration should not be so high that research subjects accept risk or discomfort they would not accept in the absence of remuneration. This means that extra credit for research participation should not be a large percentage of the student’s overall grade.
Remuneration must be equal for all participants. That means, for instance, that a professor cannot offer 1% of a student’s current course grade for filling out a survey, since that would differ from student to student. A professor could offer 1% of the total possible course grade, so that each student who participates sees their final course grade go up by 1 percentage point.
Importantly, if extra credit is offered in exchange for research participation, other students in a class must be given an alternate, non-research option for earning extra credit. This extra credit option should take the same amount of time as the research option, and be worth the same amount of extra credit. The alternate option should not be graded, as the research participation would not be graded. Students should not be allowed to do both the research option and the alternate option for extra credit.
Consider difficult situations that may arise; for instance, what to do with a student who fills out half of a survey and then decides that they are uncomfortable continuing. Will this student still get the extra credit for participating in research? In general, it is better to allow students to receive the promised extra credit for the time they spent attempting the research activity, so that they are not penalized for discontinuing participation. However, if there is any scenario where a student will not be given the extra credit – such as failing attention-check questions in a survey – this should be clearly stated in the informed consent document at the beginning of the research activity.
Additionally, in the informed consent document, special care should be paid to ensure that students know that not participating in the research will not impact their course grade negatively nor impact their relationship with the professor.