[stolio]

Unless you're testing Zen meditation in which case the placebo group and the real group may not (should not?) be distinguishable from one another.

It's often taught as "just sitting" so by the time you get the control group to sit down, shut up and hold still for half an hour every day they're doing the practice. Heck, they may be doing it better than the Zen meditators because they won't have anything extra attached to it at all :)