11+ Most Controversial Psychological Experiments in History

Here is a glimpse at some of the most controversial psychological experiments in history.
Kashyap Vyas
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Scientific experimentation is a staple of human progress. Academic researchers are usually required to abide by rules and regulations governing the ethics of conducting studies. However, there has always been a very small number of researchers that have moved far beyond what many consider is ethical. 

Today, there are strict rules that must be followed when conducting such psychological experiments. For example, the American Psychological Association (APA) has a binding Code of Conduct that must be followed when conducting any kind of experiment. Experimenters are bound to adhere to everything from consent to confidentiality of the experiments.

Moreover, there are review boards and panels who are in charge of reinforcing these strict ethics. Having said that, the norms were not always this stern. That is precisely how some of the following controversial psychological experiments came to be conducted. 

 1. The Facebook experiment

11+ Most Controversial Psychological Experiments in History
Source: hocus- focus/iStock

The Facebook Experiment of 2012 created quite an uproar amongst indignant users. Nearly 700,000 Facebook users were subjected to secret psychological tests to gauge the effects of different types of posts.

The details of the experiment came out in a scientific paper published in the Proceedings of the National Academy of Sciences. The paper revealed that, unbeknownst to users, Facebook had tampered with the news feeds of nearly 700,000 people, showing them an abnormally low number of either positive or negative posts. The experiment aimed to determine whether the company could alter the emotional state of its users.

The experiment was designed to determine whether the number of positive or negative comments in a Facebook newsfeed would have any effect on how the user updated their own page. 

News of the research led to outrage from people who felt they had been secretly manipulated by the company.

The researchers revealed that social media users were prone to “emotional contagion” in which they mimicked the type of content of others who posted on their feed. For example, those shown more negative comments posted more negative comments themselves.

Although the results were interesting, Facebook suffered a storm of criticism, with many referring to the social media platform as “terrifying” and “creepy.” The ethics of the experiment have since been debated heavily. 

 2. The Operation Midnight Climax

The US Military and CIA have an extensive history of conducting unusual psychological experiments.

One research project, dubbed Operation Midnight Climax, was conducted in the 1950s under the direction of Allen Dulles, the CIA Director at the time. It was a part of Project MKULTRA, the controversial series of experiments aimed at developing mind control techniques.

This operation was conducted with the motive of exploring the use of “mind-control” drugs and testing the effects of psychoactive drugs like LSD on individuals.

Unknowingly, clients were lured to CIA-run brothels by CIA-paid prostitutes, and psychoactive substances such as LSD were slipped into their drinks. These individuals were then monitored from behind a two-way mirror while they engaged in sexual activities.

The project's activities expanded over the years to test other agents, such as stink bombs and heroin, on many unsuspecting people. The brothels were also popular with agents, who used them for "quickies."

The agency shut down MKULTRA in the late 1960s after the CIA’s inspector general’s office discovered the experiments. However, two related programs, MKSEARCH and Project OFTEN, continued until 1972 and 1973, respectively.

3. The Aversion Project

The South African Aversion Project was yet another unethical psychology experiment that was conducted on people. Apartheid South Africa was an extremely dangerous place for homosexuals — both black and white. During that time, the government had strict anti-homosexual laws. Being gay was defined as abnormal and homosexuality was considered a mental illness. As a result, aversion therapies and techniques were applied to many South Africans to "cure" them of this illness.

Homosexuals were also often forced to join the military against their will. The Aversion Project mainly consisted of drugging lesbians and gay men, they were subjected to electroconvulsive behavior therapy. In this therapy, the homosexuals were shown photos of same-sex erotica after drugging them.

Thereafter, they were electrically shocked, and they were shown pictures of the opposite sex erotica. The technique obviously did not work, and the victims were then subjected to hormone therapy.

In some cases, this therapy also included chemical castration. Moreover, more than 900 men and women were forced to undergo a gender reassignment surgery to reorient them, without their consent, of course.

4. Unnecessary sexual reassignment experiments

11+ Most Controversial Psychological Experiments in History
David Peter Reimer. Source: WP

One tragic case came about as the result of poor decisions made after a surgical accident, when a seven-month-old Canadian boy was “accidentally castrated” while undergoing a routine circumcision.

After the penis of David Peter Reimer was accidentally maimed, a psychologist convinced his parents that the boy was more likely to successfully reach sexual maturation if he underwent sexual reassignment surgery as a female.

The psychologist, John Money, reported the reassignment was successful and used it as evidence that gender identity is primarily learned. However, as Reimer grew older, he came to realize that he was not a girl and at the age of 15, he transitioned to living as a male. Reimer eventually went public with his story to help discourage similar medical practices and the resulting furor changed medical practices in similar cases. Reimer killed himself at the age of 38, after suffering severe depression.

5. The Milgram Experiments

11+ Most Controversial Psychological Experiments in History
Milgram experiment advertisement. Source: Wikimedia

A psychologist from Yale University named Stanley Milgram conducted one of the most notorious studies on obedience.

His psychological experiment consisted of analyzing the conflict between personal conscience and obedience to authority. In 1963, Milgram examined justifications that were offered by people accused of performing acts of genocide during World War II.

More often than not, they offered a defense based on the notion of “obedience” and argued that they were merely following their superior’s orders. Therefore, Milgram wanted to examine whether the Germans were somehow naturally obedient, or there was another reason behind the cruelty.

Based on this experiment, Milgram chose participants through newspaper advertising, urging them to participate in a study at Yale University.

Each participant was then paired with another participant. One was the "learner", and the other was the "teacher". In each case, the learner was actually a confederate of Milgram who was pretending to be an actual participant.

The learner was taken to one room and the teacher was taken to the other. The teacher’s room consisted of an electric shock device, along with a row of switches labeled from 15 volts to 450 volts.

The aim of the experiment was to research exactly how far people were willing to go in order to obey an instruction, even if that entailed harming another person. The teacher was instructed to "shock" the student with increasingly high voltages. However, unbeknownst to the teacher, the switches were not real and the learner was faking their reaction. The fake electric shocks gradually increased to levels that would have been fatal had they been real.

The experiment found, unexpectedly, that a very high proportion of subjects would fully obey the instructions, albeit reluctantly.

6. The Stanford Prison Experiment

11+ Most Controversial Psychological Experiments in History
Source Eric. E Castro/Wikimedia

The SPE experiment was conducted in 1971 at Stanford University. It was one of the most compelling psychological studies and has become particularly notorious.

In the study, participants were assigned as either guards or inmates in a mock prison at the university. 

The premise of the experiment was that when people are given a certain amount of power over others, they will eventually start to abuse that power. On the flip side, people who are put in a powerless situation will often be driven to submission or even madness.

The experiment found that people who were assigned the role of guards became progressively more cruel and even became willing to inflict psychological torture, while many of the "inmates" passively accepted psychological abuse and actively harassed other prisoners who tried to stop it.

The experiment was abandoned early, has been criticized for using an unscientific methodology, such as instructing the participants on how to behave, and its findings have been called into question,  

7. The Monster Study

The Monster Study experiment of 1939 was an admirable experiment on the part of Dr. Wendell Johnson, who was a speech pathologist. He wanted to understand the cause of stuttering. Therefore, he conducted an experiment on a group of children at an orphanage in Davenport Iowa. Johnson did not agree with the prevalent belief that stuttering was an inborn trait which therefore could not be corrected.


As a part of the study, Johnson experimented on 22 orphans and put them into two groups of stutterers and non-stutterers.

Only half of the kids in the stuttering group were actually stutterers. Throughout the experiment, the non-stutterers enjoyed heavy praise, thanks to their conventional speech patterns.

On the other hand, the stuttering group continually received negative reinforcement, and they were always put on edge as a reminder not to stutter. Johnson concluded afterward that the kids who did have stutters in the stuttering group were actually worse off than before and the ones in the stuttering group who hadn't stuttered before the experiment started stuttering by the end of the experiment.

Johnson established that the problem of stuttering was developmental instead of an innate trait, but he left many children with a lifelong struggle.

 8. The 1969 Monkey Drug Trials

11+ Most Controversial Psychological Experiments in History
Source: 13160449/iStock

The Monkey Drug Trial in 1969 is another one of those psychological experiments that entirely crossed the line.

Despite this trial helping psychologists understand drug addiction better, the three researchers who conducted this experiment at the University of Michigan Medical School completely overstepped their mark, making it another psychological experiment gone wrong.

The researchers hooked Macaque monkeys on illegal substances by injecting the unwitting primates with drugs such as cocaine, morphine, amphetamines, and alcohol.

They did this to see if the monkeys would later actively administer doses of these substances to themselves.

Many monkeys did, and the researchers were able to establish a link between psychological dependence and drug abuse. However, the experiment had questionable scientific value, as the same results might not be reproducible in humans.

In addition to that, despite the establishment of a link, the method was definitely unethical as well as cruel because some of the monkeys died during the experiment.

9. The Robbers Cave Experiment

11+ Most Controversial Psychological Experiments in History
Source: Cummings Center for the History of Psychology/YouTube

The Robbers Cave Experiment was organized by the psychologist Muzafer Sherif in the Robbers Cave State Park, Oklahoma.

Sherif recruited boys of the age group of 11 and 12 for the experiment and split them into two groups. The boys developed an attachment to their groups throughout the first week of the camp by doing various activities together, such as hiking, swimming, etc.

The two groups then spent four days competing with each other in many games. During the competitions, Sherif manipulated the results of the game to bring the game scores exceptionally close. During the competitions, prejudice between the groups began to become apparent.

There then followed a two-day cooling-off period, where the boys tended to characterize their own group in very favorable terms, and the other group in very unfavorable terms.

Sherif then attempted to reduce the prejudice, or inter-group conflict. However, simply increasing the contact of the two groups only made the situation worse, whereas forcing the groups to work together to reach common goals, eased prejudice and tension among the groups.

The experiment confirmed Sherif's realistic conflict theory (also called realistic group conflict theory) — the idea that group conflict can result from competition over resources.

This experiment is clearly controversial as it uses children as test subjects without their consent or even awareness.

 10. The Brown-Eyed vs. Blue-Eyed Student Experiments

11+ Most Controversial Psychological Experiments in History
Source: wcfcourier

Jane Elliott was a third-grade teacher who became known for her brown eyes/blue eyes exercise. This experiment went on to demonstrate the impact of racism on education.

The morning after the assassination of Martin Luther King, Elliott told her class that the way in which things were done was going to change. She placed the blue-eyed children at the front of the classroom.

They were given additional recess time, the pride of place in the front of the classroom, a second helping of food during lunch, and active participation in class discussions.

At the same time, the brown-eyed children had to sit at the back of the class; moreover, they were severely reprimanded for all those things that the blue-eyed kids usually got away with. Elliott even went through all the trouble of making up a scientific fact that supposedly stated blue-eyed people to be more intelligent than brown-eyed ones, thanks to the presence of melanin.

The results of the study were stunning. The blue-eyed students performed much better in the assignments whereas those brown-eyed students who usually showed a much better performance in the class were found struggling.

The blue-eyed students also became vicious towards the brown-eyed ones. The next day, Elliott reversed the exercise, and the same results were found. However, the brown-eyed students were not as vicious with their taunts. At the end of the exercise, both the groups of children hugged each other and cried. They had learned an essential lesson in racism, even though the process was completely unethical.

 11. The Little Albert Experiment

The Little Albert Experiment
Source: John B Watson/Wikimedia

John Watson is a popular psychologist, and people know him as the “Father of Behaviorism.” He was known to use orphans in many of his experiments.

In one of these especially unethical and well-known experiments, Watson employed Little Albert, an orphan of nine months old.

In this experiment, Watson exposed Little Albert to many sights and sounds. This included monkeys, rabbits, different masks, and a burning newspaper. In the second part of the experiment, Little Albert was introduced to a white rat.

Much like the earlier things, Little Albert was not scared of the rat. But then, every time Albert touched the rat, Watson made loud noises with a bar made of steel.

This distressed Little Albert as he thought that the noise was coming from the rat. Over time, he showed fear of anything white and/or fluffy. This demonstrated Watson’s hypothesis that it was possible to condition the element of fear in people.

12. Project QKHILLTOP

11+ Most Controversial Psychological Experiments in History
Source: Mike Mcclaughry

Project QKHILLTOP was a CIA developed experiment to study Chinese brainwashing techniques. This shocking psychological experiment was born out of the CIA's desire to create more effective methods of interrogation. Led by Dr. Harold Wolff of Cornell University Medical School, the controversial experiments explored drugs, imprisonment, deprivation, humiliation, torture, brainwashing, and hypnoses on various subjects. 

13. University of Pennsylvania testing prison inmates 

11+ Most Controversial Psychological Experiments in History
Source: Graphics8

In 1951 researchers from the University of Pennsylvania began experimenting on inmates at Philadelphia’s Holmesburg Prison. For 20 years, Dr. Albert M. Kligman tested toothpaste, deodorant, shampoo, skin creams, detergents, liquid diets, eye drops, foot powders, and hair dyes on inmates' skin, to determine if they were safe to use. The tests required constant skin biopsies and painful procedures. 

History has shown the cruelty of humans towards other human beings and species in their quest to find answers to some questions. In this quest, they forgot about ethics and morals which led to severe repercussions and in some cases, scarred adulthood where children are involved.

However, it is good that people have learned from history and now, researchers need to seek prior permission before conducting experiments with human subjects.

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