You can definitely get high with a placebo. I have seen people in festivals getting high just by touching people, the "explanation" being that the people were sweating the drugs and by touching enough of them, you get enough for yourself to get high. This is as convincing to me as homeopathy, so definitely placebo, and it happened to people who took these drugs before and are familiar with their effects.

And here, they are not giving you a big dose of MDMA so you can dance until sunrise, they are giving you a moderate dose of amphetamines to (tentatively) boost your ability to solve a maths problem.

Unless you have already trained yourself, don't overestimate your ability to discriminate, the placebo effect is really strong here.