Abstract: Placebo treatment initially was a controlled condition in studying certain active therapeutic effect, but now it has been the study object that the investigators who are interested in. And the experimental paradigm also has kept changing accordingly. Randomized and double-blind design concerns about if the active therapy is more effective than placebo treatment; Deceptive design investigates placebo effect itself by directly compared the placebo treatment and natural history condition; Open-hidden paradigm estimates the size of placebo effect by subtracting hidden effect from open effect; Balanced paradigm can observe placebo effect and therapeutic effect simutaneously; Reinforcement paradigm can produce strong placebo effect with conditioned reinforcement and is an optimized paradigm for studying the mechanism of placebo effect; Transferable paradigm built by our team, can observe the transferable effect from pain domain to emotion domain, is a complement to reinforcement paradigm.

Key words: placebo effect, experimental paradigm, placebo expectation