This Don Mayne cartoon touches on some important issues.  1. When a trial has at least perceived risks, there should be a process where the chief investigator explains those risks to potential participants as well as the strategies to mitigate them.  2. Taking care lest an incentive trivialises a project and its significance.  3. Should a helper/technician ever be the person who speaks with participants?  These are matters that should be discussed in institutional guidance material, rather than a research ethics committee attempting to cover it in review feedback.