I like how this response is just as relevant to your non-IRB approvable study on what stimuli cause more effort.
Please tell me that I not the first person to note the (ethically difficult) deceptiveness of that study, even if the results are interesting.
Why is it ethically difficult? (I don't particularly care whether it passes a university ethics review, I base whether I consider it ethical on my emotional reaction to it and emotional reaction to its consequences)
Master copy lives on gwern.net