> There is no placebo effect here that's possible because, well, it is impossible for someone to believe they have taken a full dose of pscychodelic drugs and not feel anything.

From what I recall, a low dose of methylphenidate is used as a control in many studies because it has some of the same side effects without the trip. For psychedelic-naive people who don’t really know what to expect, I could see it being an ok control. Once you’ve experienced a single high-dose trip though… yeah… you’re never going to trick someone with it.