[astine]

"That depends on people believing polygraphs work though"

Are you sure that's true? In medicine, apparently placebos have an effect even if you know that it's a placebo. I imagine that even if you know that it's theoretically useless, being hooked up to a machine that can read your vitals while lying would still be nerve wracking.

[ampdepolymerase]

Having an effect is different from being able to sell a product based on that effect. For regulated fields like pharmacy, the FDA regulatory approval test requires proving efficacy against a placebo. A doctor may (under certain specific circumstances) treat a patient using a placebo (because medicine's aim is to do whatever that is necessary to alleviate the problem or reduce suffering, it is different from pure biological natural sciences/pharmacy where inferences must be backed up by scientific theory and validated by empirical evidence) but it does not necessarily mean that a placebo can be sold/marketed as a cure.

[roel_v]

To a degree of course, just 'but it might work' would be enough I guess, the same way someone needs to at least not be told something is a placebo for a double blind study to be "valid" ("methodologically sound" would a better term I think?). I did read quite a lot on the topic and much has been written about it over the years, but this was 10+ years ago for me, I don't remember enough to really make a coherent argument that addresses the details.