Sorta. If you are worried about placebo/nocebo, than I see obvious paths where you wind up in with your incentives being to lie to people. Either about the possible ill effects, or about enthusiasm that they will work.
Yes, we have evidence that this influences things. That is usually why people replicate without telling people why they were doing something. In this study, they didn't say "we are testing you with masks to see if they make you test better." It was more, we are testing you with and without masks to see if we spot differences. I could easily envision some folks expecting the result to go the other way.
More, if that is the concern, you need to test doing that. Don't make it blind, reverse the message. Tell them you expect them to be less alert wearing a mask, and see if that holds.
Could work. I don't know enough about the specifics of experiment design for sleep research. You could also try things like transparent masks + lies ("they filter specific wavelengths"), etc. Studying people is awfully hard. Lying is generally allowed as long as you do the right things as far as advance ethics review and design (and usually informing the person later, etc.).
To be fair, the problem you are bringing up is larger than just sleep research. https://examine.com/summaries/study/0AKk3d/ is an interesting study that was looking at what is often thought of as a much more active drug.
My question is ultimately on whether that is a flaw in this study, or more to study? :D I'm probably placing too much weight on the word "flaw?"
Studying people is so complicated with so many weird results you really just need to make it double blind, you won't be able to reason your way out of it reliably.
Yes, we have evidence that this influences things. That is usually why people replicate without telling people why they were doing something. In this study, they didn't say "we are testing you with masks to see if they make you test better." It was more, we are testing you with and without masks to see if we spot differences. I could easily envision some folks expecting the result to go the other way.
More, if that is the concern, you need to test doing that. Don't make it blind, reverse the message. Tell them you expect them to be less alert wearing a mask, and see if that holds.
Right?