The Monster Study is an investigation that was carried out in the United States in the 1930s and aimed to find out the effects of different therapies on children with language and communication disorders.

This study has generated debates and controversies that have marked an important part of research in psychology, specifically with respect to its ethical dilemmas. Below we explain what the Monster Study is, how it was approached and what are the reasons why it is considered controversial research .

What is the Monster Studio?

The Monster Study is an investigation into language fluency disorder (stuttering) , which was conducted by the American psychologist Wendell Johnson in 1939. It was carried out under Johnson’s supervision, but directly conducted by one of his graduate students, Maria Tudor.

The research was conducted at the University of Iowa and involved twenty-two orphaned children from the veterans’ orphanage also in Iowa. The main goal of the study was to analyze whether stuttering could be induced and whether it could be decreased with positive reinforcement therapy.

In contrast to the brain theories that were gaining ground in his time, Wendell believed that stuttering is a learned behaviour , and that as such, it could be unlearned as well as induced.

According to the psychologist, stuttering occurs when the person listening to someone with slurred speech evaluates this as undesirable; this is perceived by the person speaking and causes him/her tension and concern.

The consequence of this tension and worry is that the speaker worsens the fluency of his speech; this generates more distress and again causes the stuttering. In other words, for Wedell stuttering is a consequence of the effort to avoid stuttering, which is caused by the pressure exerted by the listener.

Studio design

The Monster Study began by selecting the 22 children who participated. Of those 22 children selected, there were 10 who had a stutter previously detected by their teachers and caregivers.

Afterwards, Tudor and his research team personally evaluated the children’s speech. They generated a scale of 1 to 5 where 1 referred to the lowest fluency; and 5 referred to the highest fluency. Thus, they divided the group of children: 5 of them were assigned to an experimental group and the other 5 to a control group.

The other 12 children who participated did not have any language or communication disorder and were also randomly selected from within the orphanage . Six of these 12 children were also assigned to a control group and the other 6 to an experimental group. They were between 5 and 15 years old.

None of the children knew they were participating in research; they believed they were actually receiving therapy that would last 4 months, from January to May 1939 (the length of the study).

Maria Tudor had prepared a therapy script for each group. To half of the children she would say some sentences in positive, trying to make the children stop paying attention to the negative comments that others make about their speech; and to the other half she would say those same negative comments and emphasize every mistake in their speech .

Main results

The 22 children were divided according to whether they had a language disorder or not, into a control group and an experimental group. The children in the experimental group received speech therapy based on positive reinforcement. This included, for example, praising the fluency of their speech and words. This applied to children who had stuttering as well as to those who had little or no stuttering.

To the other half of the children, those in the control group, Tudor gave therapy based on the opposite: negative reinforcement. For example, exalted every imperfection of language, belittled speech, emphasized that they were “stuttering children” ; and if the children did not present any disorder, he told them that they were not speaking well and that they were presenting the first symptoms of stuttering.

The only conclusive result was that the participants in this last group quickly showed symptoms of anxiety, especially because of the embarrassment of speaking, which is why they began to correct each speech obsessively, and even avoid communication. Their schoolwork declined and their behavior changed towards withdrawal.

Why is it known as a “monster” study?

This study is known as a “monster” because of the ethical dilemmas it has generated . The group of children who received the therapy based on negative reinforcements, presented psychological effects that were also negative in the long term, in addition to the fact that those who already had language disorders, kept them throughout their lives.

Once the study was over, Tudor returned to the orphanage voluntarily to offer help to those who had developed anxiety and for those who had worsened their speech fluency. He even tried positive reinforcement therapy .

Likewise, Johnson apologized a year later saying that the children would surely recover in time, even though it was clear that his study had left an imprint on them.

Johnson colleagues dubbed this research the “Monster Study,” calling it unacceptable that orphaned children should be used to test a hypothesis. Today, and after several similar cases, the ethical standards of research in psychology have been significantly reformulated.

After being hidden, this research came to light and caused the University of Iowa to publicly apologize in 2001 . This same university faced a demand for thousands of dollars from several of the children (now adults) who had been affected in the long term by the research.

Bibliographic references:

  • Goldfarb, R. (2006). Ethics. A Case Study from Fluency. Plural Publishing: USA
  • Polti, I. (2013). Ethics in research: analysis from a current perspective on paradigmatic cases of research in psychology. Paper presented at the V International Congress on Research and Professional Practice in Psychology. School of Psychology, University of Buenos Aires, Buenos Aires. Online] Available at
  • Rodríguez, P. (2002). Stuttering from the perspective of stutterers. Central University of Venezuela. Retrieved May 12, 2018. Available at