The Monster Study (1939)

University of Iowa's Monster Study deliberately induced stuttering in 22 orphan children through negative therapy, with over 50% developing lifelong speech problems—a harm rate that outpaces the side-effect incidence in any modern clinical trial. Researcher Wendell Johnson told orphans they were stutterers, criticizing every imperfection. The experiment was suppressed for decades until 2001. Iowa apologized and settled a lawsuit with six survivors in 2007.