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In 1939, researchers at a prominent American university began an experiment involving children at an orphanage in Iowa.
The children were divided into groups, subjected to very different forms of speech therapy, and in some cases told that something was wrong with the way they spoke.
The study was never formally published, and for decades, few people outside a small academic circle knew what had happened.
Learn more about the Monster Study, one of the most controversial experiments in the history of psychology, on this episode of Everything Everywhere Daily.
One of the most controversial experiments ever conducted in psychology took place in 1939 at the University of Iowa, led by researcher Wendell Johnson.
Born in 1906 in Kansas, Johnson grew up as the youngest child of Swedish immigrants on a farm. Around age 5 or 6, Johnson developed a stutter, which caused him to be sent to schools to try to fix his speech impediment.
Despite his speech impediment, Johnson was a force in his everyday life. He was captain of multiple sports teams at his school, president of his high school class, and valedictorian. After graduating, he spent two years at his local college before attending the University of Iowa.
Johnson is considered one of the earliest and most influential speech pathologists. He dedicated his life to researching stuttering and trying to find its cause and a cure. He was the first to introduce general semantics into the field of speech pathology. His data remains the largest collection of scientific information on stuttering onset and fundamentally changed how stuttering research is approached and taught.
However, today he is probably best known for a controversial study he conducted in 1939.
Johnson proposed that stuttering is a learned behavior, not a biological one. This idea came from his childhood experiences. He stated, “Stuttering often begins not in the child’s mouth, but in the parent’s ear.”
If he could prove the hypothesis, it would have massive implications for speech therapy, and of course, his career.
To conduct the experiment, in 1938, Johnson recruited one of his graduate students, Mary Tudor, as his assistant. They decided to conduct the experiment at the Iowa Soldiers’ Orphans Home in May 1939.
The experiment aimed to induce stuttering in non-stuttering children. They believed that they could do this by telling the children that they stuttered. For children who already stuttered, they believed they could eliminate the speech disorder by telling them they spoke fine.
Tudor and five other graduate students screened 256 kids for the experiment. The group listened to the children speak and graded them on a scale of 1 to 5, with 1 indicating poor speech fluency and 5 indicating fluent speech.
After the initial screening, the researchers selected 22 children as subjects. They ranged from 5 to 16 years old. The orphanage staff and the subjects were not told about Tudor’s research and believed they were attending speech therapy sessions.
Of the 22 kids, 10 were marked as “stutterers,” and 12 were deemed to be “normal” speakers before the experiment’s start. The 10 children who stuttered were then divided into 2 different groups.
The first Group was 1A, or the experimental group. Five stuttering children were told that their speech had no problems and that they did not stutter.
The second group of 5, group 1B, was the control group. The five kids were told that their speech was just as bad as they were told previously and received traditional speech therapy.
The 12 non-stuttering children were also split into 2 groups.
Group 2A was the experimental group, where the controversy surrounding the experiment lay. Six of the “fluent” children were told that their speech was absolutely horrible and that they were starting to develop a stutter. They were told this was an urgent issue that must be corrected immediately and that they could not speak unless they spoke without a stutter.
The second group, 2B, was another control group. The six “fluent” children were told they did not stutter and were complimented on their pronunciation.
During the children’s first visit with Tudor, she tested their IQ and whether they were right- or left-handed. They tested handedness because, at the time, a popular theory held that a cerebral imbalance caused stuttering.
The theory was that if a person was born left-handed but used their right hand, their nerve impulses would misfire. Because of this misfiring, the person’s speech would be impacted. Johnson was not a believer in the left hand/right hand theory, but did want Tudor to test each handedness to see if there was credence to the idea.
To test their handedness, Tudor had them draw on chalkboards and squeeze a dynamometer, which physical therapists use to measure hand and muscle strength.
Most of the kids were right-handed, but both groups included left-handed kids. Researchers gave these kids special numbers to identify them.
Tudor’s intervention occurred every few weeks. When she arrived at the orphanage, she would speak to each child for 45 minutes. During these 45 minutes, she followed a previously agreed-upon script.
She told the children in Group 1A they would outgrow their stuttering and speak significantly better than they do right now. She told them not to pay attention to what other people said about their speaking ability and that stuttering was just a phase.
As for the non-stuttering experimental group, Group 1B, she told them they stuttered and that the staff agreed they were having trouble with their speech. They were told they were showing symptoms of kids who were beginning to stutter.
From there, the children were given negative speech therapy. This made them hyper-aware of how they spoke. The kids were told to take a breath if they thought they would stutter, stop speaking if they thought they were going to stutter, place their tongues on the roof of their mouth, do anything to prevent stuttering, and watch their speech at all times.
She then told the child to try to stop stuttering immediately with all their willpower and not to speak unless they were confident they were speaking correctly.
The non-stuttering experimental group responded immediately. For example, after Tudor’s second session with a 5-year-old girl, she found it difficult to get her to speak, despite speaking freely in their prior meeting.
Another child, a 9-year-old girl, refused to talk, and a 15-year-old girl reportedly became self-conscious, spoke significantly less, and snapped her fingers in frustration. When Tudor asked the 15-year-old girl why she kept saying “a” so much, the girl reported being scared she couldn’t say the next word and snapped to stop saying “a.”
Additionally, the group’s overall schoolwork worsened; some children refused to speak in class and began constantly correcting their speech. When asked why, one child said their words felt stuck.
The children receiving negative speech therapy showed increased self-consciousness, reluctance to speak, and other changes in their communication, and some later reported lasting psychological and speech-related difficulties.
As for the kids who had a stutter and were told their speech was fine, they were given positive reinforcement. There was some improvement in fluency and stability, but their impediment was not cured.
Mary Tudor was personally affected by the experiment. and felt bad about the negative speech therapy she subjected the children to. She returned to the orphanage 3 times after the experiment to give follow-up care, fearing she could not reverse their effects.
Tudor’s master’s thesis was never formally published as a journal article, and the study remained obscure outside the speech-pathology community for decades. However, it was an open secret in speech pathology, as the University of Iowa attracted leading researchers in the field.
The center came to call the experiment the “Monster Study” in the 1940s and 50s. It is believed they gave it this name because academic peers at the University of Iowa were horrified by the experiment’s unethical methods.
Wendell Johnson died in 1965, before the public became aware of the experiment. A 1988 article published in the “Journal of Fluency Disorders” suggests that the experiment was never published because its conclusions were embarrassing.
The experiment remained hidden from the public eye for 62 years until 2001.
Reporter Jim Dyer brought it to light in 2001 with an investigative series in the San Jose Mercury News, exposing the Monster Study after examining Mary Tudor’s long-overlooked 1939 thesis and locating surviving participants.
Dyer was reportedly horrified by the experiment and reached out to the test subjects to better understand what had happened and its impact on the children.
Several of the children who were involved had died, but some were still alive and shared with Dyer their experiences. Through his interviews, it was discovered that some of the children involved in the experiment had long-lasting psychological effects. For example, one woman involved in the experiment was horrified to learn she had been part of it. She was never told it was conducted without her knowledge or consent.
Having spent her entire life under the impression that she stuttered, that same woman reportedly pulled back from various aspects of her life. Other participants likewise described becoming reserved and deeply self-conscious regarding their speech.
Some subjects, after learning about the experiment, believed it had ruined their lives. They said believing they stuttered made people make fun of them, which led to their grades falling and them feeling stupid. They believed that the experiment took away opportunities to become something better in life due to their anxiety over their speech.
Tudor was also interviewed about her part in the experiment. She said she carried deep guilt about it and that, if she were tasked with conducting the experiment today, she would not do it. However, she defended her actions by saying she was following orders.
After the articles were released, the University of Iowa issued an apology. Despite the unethical experiment, the University of Iowa still has the “Wendell Johnson Speech and Hearing Clinic,” which remains a leading educational center for stuttering research.
The study became notorious primarily for its ethical problems rather than for establishing the cause of stuttering. Johnson’s theory that stuttering could develop largely through parents or others labeling normal childhood disfluencies as stuttering was influential for a time, but it is no longer considered an adequate explanation of the disorder. Modern research indicates that developmental stuttering is a complex neurodevelopmental condition involving genetic, neurological, and other factors.
Defenders of Johnson have argued that research standards were very different in 1939 and that the experiment should be evaluated in the context of the ethical norms of its era.”
The surviving children from the experiment, along with the families of those who had passed away, filed a lawsuit against the state of Iowa for the monster experiment. The state initially tried to dismiss the lawsuit, but the Iowa Supreme Court agreed to hear the case.
In August 2007, the State of Iowa agreed to pay a total of $925,000 to six plaintiffs, including surviving participants and representatives of deceased participants.
In the years that have passed, the American Speech-Language-Hearing Association has prohibited experimentation on children where there is a chance of lasting harmful consequences. Children can still be studied, but researchers must provide strong justification before exposing any child to research risks.
The Monster Study remains one of the most infamous examples of how scientific curiosity can collide with basic ethical responsibilities.
The experiment was hidden from the public for decades, but its eventual exposure helped turn it into a cautionary tale about informed consent and the limits that must be placed on human experimentation.