Which event led to the decline of Franz Mesmer’s brand of hypnosis?

Mesmer’s theory of animal magnetism was tested in a scientifically controlled experiment by a commission that included Benjamin Franklin. The commission found that people could experience the supposed effects even when they did not know they were being treated, suggesting imagination—not a magnetic force—was responsible. This experiment helped discredit Mesmer’s brand of hypnosis, so the correct choice is “a scientifically controlled experiment.”

AI-written and checked against the verified answer.