The Monster Study (1939)

University of Iowa researcher Wendell Johnson experimented on 22 orphan children, deliberately inducing stuttering in normally fluent children through negative speech therapy — telling them they were stutterers and criticising every imperfection. Some children who received the negative therapy developed lifelong speech problems. The experiment was suppressed for decades and only became public in 2001. The University of Iowa apologised and settled a lawsuit with six of the surviving orphans in 2007.