The 10 Cruelest Human Experimentation Cases in History

The 10 Cruelest Human Experimentation Cases in History

D.G. Hewitt - May 20, 2018

“First, do no harm,” is the oath taken by physicians the world over. And this has been the case for centuries now. For the most part, these men and women of science stay faithful to this oath, even defying orders to the contrary. But sometimes they not only break it, they do so in the worst way imaginable. There have been numerous instances of doctors and other scientists going way beyond the limitations of what’s moral or ethical in the name of ‘progress’. They have used humans as experimental guinea pigs for their tests.

In many cases, the test subjects were either kept in ignorance about what an experiment involved or they were simply in no position to offer their resistance or consent. Of course, it may well be the case that such dubious methods produced results. Indeed, some of the most controversial experiments of the past century produced results that continue to inform scientific understanding to this day. But that will never mean such experiments will be seen as just. Sometimes, the perpetrators of cruel research lose their good names or reputations. Sometimes they are prosecuted for their attempts to ‘play God’. Or sometimes they just get away with it.

You might want to brace yourself as we look at the ten weirdest and cruelest human experiments carried out in history:

The 10 Cruelest Human Experimentation Cases in History
Despite his many cruel human experiments, Yishii escaped prosecution. Wikimedia Commons.

Dr. Shiro Ishii and Unit 731

During World War II, Imperial Japan committed a number of crimes against humanity. But perhaps few were crueler than the experiments that were conducted at Unit 731. Part of the Imperial Japanese Army, this was a super-secret unit dedicated to undertaking research into biological and chemical weapons. Quite simply, the Imperial authority wanted to build weapons that were deadlier – or just crueler – than anything that had gone before. And they weren’t opposed to using human guinea pigs to test their creations.

Based in Harbon, the biggest city of Manchuko, the part of north-east China that Japan made its puppet state, Unit 731 was constructed between 1934 and 1939. Overseeing its construction was General Shiro Ishii. Though he was a medical doctor, Ishii was also a fanatical soldier and so he was happy to set his ethics aside in the name of total victory for Imperial Japan. In all, it’s estimated that as many as 3,000 men, women and children were used as forced participants in the experiments conducted here. For the most part, the horrific tests were carried out on Chinese people, though prisoners-of-war, including men from Korea and Mongolia, were used.

For more than five years, General Ishii oversaw a wide range of experiments, many of them of dubious medical value to say the least. Thousands were subjected to vivisections, usually without anaesthetic. Often, these were fatal. Countless types of surgery, including brain surgery and amputations, were also carried out without anaesthetic. At other times, inmates were injected directly with diseases such as syphilis and gonorrhoea, or with chemicals used in bombs. Other twisted experiments included tying men up naked outside and observing the effects of frostbite, or simply starving people and seeing how long they took to die.

Once it was clear Japan was going to lose the war, General Ishii tried to destroy all evidence of the tests. He burned down the facilities and swore his men to silence. He needn’t have worried. Senior researchers from Unit 731 were granted immunity by the U.S. In exchange, they contributed their knowledge to America’s own biological and chemical weapons programs. For decades, any stories of atrocities were dismissed as ‘Communist Propaganda’. In more recent years, the Japanese government has acknowledged the Unit’s existence as well as its work, though it maintains most official records have been lost to history.

The 10 Cruelest Human Experimentation Cases in History
Baby ‘Albert’ was traumatized by doctors in the name of science. Psychology Today.

“The Little Albert Experiment”

After many months observing young children, John Hopkins University psychologist Dr. John B. Watson concluded that infants could be conditioned to be scared of non-threatening objects or stimuli. All he needed was first-hand proof. Since it was 1919 and experimental ethics were nowhere near as strict as they are today, Watson, along with his graduate student Rosalie Rayner, set about designing an experiment to test their theory. Thanks to their connections at the Baltimore hospital, they were able to find a young baby, named ‘Albert’, and ‘borrow’ him for the afternoon. While Albert’s mother might have consented to her son helping out scientific research, she had no idea what Watson was actually planning.

The young Albert was just nine months old when he was taken from a hospital and put to work as Watson’s guinea pig. At first, Watson carried out a series of baseline tests, to see that the child was indeed emotionally stable and at the accepted stage of development. But then the tests got creepier. Albert was shown several furry animals. These included a dog, a white rat and a rabbit. Watson would show these toys to Albert while at the same time banging a hammer against a metal bar. This was repeated a number of times. Before long, Albert was associating the sight of the furry animals with the fear provoked by the loud, unpleasant noise. Indeed, within just a short space of time, just seeing the furry rat could distress the child.

Watson noted at the time: “The instant the rat was shown, the baby began to cry. Almost instantly he turned sharply to the left, fell over on [his] left side, raised himself on all fours and began to crawl away so rapidly that he was caught with difficulty before reaching the edge of the table.” The scientist and his research partner had achieved their goal: they had proof that, just as in animals, classical conditioning can be used to influence or even dictate emotional responses in humans. Watson published his findings the following year, in the prestigious Journal of Experimental Psychology.

Even at the time, Watson’s methods were seen as unethical. After all, isn’t a doctor supposed to ‘do no harm’? What’s more, Watson never worked with Little Albert again, so he wasn’t able to reverse the process. But still, the results were heralded as a breakthrough in our understanding of popular psychology. Notably, Watson recorded the Little Albert Experiment, and the videos can be seen online today. And, for what it’s worth, most experts now agree that, though he would have most likely feared furry objects for a short spell of time during his childhood, Little Albert probably lost the association between cute toys and loud noises.

The 10 Cruelest Human Experimentation Cases in History
In the ‘Monster’ experiment, orphan children were scolded for speech errors. CBS News.

The “Monster” Study

These days, any tests carried out on children are subject to strict ethical rules and guidelines. This wasn’t the case back in the 1930s, however. So, when Wendell Johnson, a speech pathologist at the University of Iowa, wanted to carry out research on young participants, his institution was happy to oblige. Along with Mary Tudor, a grad student Johnson was supervising, work began in 1939. Over the next few years, dozens of kids would be subject to speech-related tests, with the effects of the experiment lasting for decades.

The purpose of the research sounded noble enough: Johnson wanted to see how a child’s upbringing affects their speech. In particular, he was fascinated by stuttering and determined to see what made one child stutter, yet another speak fluently. Thankfully, a local orphanage was able to ‘supply’ Johnson and Tudor with 22 children for them to work with. All of the young participants spoke without a stutter when they arrived at the University of Iowa labs for the first time. They were then divided into two equal groups, and the experiment got underway.

Both groups were asked to speak for the researchers. How they were treated, however, was completely different. In the first group, all of the children received positive feedback. They were praised for their fluent speech and command of the English language. The second group received the opposite kind of treatment. They were ridiculed for their inability to speak like adults. Johnson and Tudor would listen carefully for any little mistakes, and above all for any signs of stuttering, and criticize the children harshly for them.

Johnson’s methods shocked his academic peers. Not that they would have been so surprised. As a young researcher at the University of Iowa, he gained a reputation for experimenting with shock tactics. For instance, as a postgraduate student himself, Johnson would work with his colleagues trying to cure his own stutter, even electrocuting himself to see if that made a difference. But still, inflicting deliberate cruelty on children was seen as a step too far. As such, the Iowan academics nicknamed Johnson’s 1939 research ‘The Monster Study’. And the name was just about the only thing of significance it gave us.

With the University of Iowa keen to distances itself from news of human experimentation being carried out by the Nazis in war-torn Europe, they hushed-up the Monster Study. None of the findings were ever published in any academic journal of note. Only Johnson’s own thesis remains. The effects were clear, however. Many of the children in the second group went on to develop serious stutters. Some even had serious speech problems for the rest of their lives. The university finally acknowledged the experiment in 2001, apologising to those involved. Then, in 2007, six of the original orphan kids were awarded almost $1 million in compensation for the psychological impact Johnson’s work had on them.

Interestingly, however, while the methods used for the Monster Study have widely been condemned as being cruel and simply indefensible, some have argued that Johnson may have been onto something. Certainly, Mary Tudor said before her death that she and her research partner might have made serious contributions to our understanding of speech and speech pathology had they been allowed to publish their work. Instead, the experiment is now shorthand for bad science and a complete lack of ethics.

The 10 Cruelest Human Experimentation Cases in History
The Stanford Prison Experiment has become an infamous look into the human condition. CBS News.

The Stanford Prison Experiment

Off all the ill-advised – and indeed, cruel – experiments North American universities have carried out over the decades, none is more infamous than the Stanford Prison Experiment. It’s so famous, in fact, that movies have been made based on the experiment which took place at Stanford University for one week in August 1971. Furthermore, while undoubtedly cruel, its findings are still used to inform popular understanding of psychological manipulation. Moreover, the behaviour of the participants involved is often held up as a warning about what can happen if humans are given power without accountability.

The experiment was led by Professor Phillip Zimbrano. As a psychologist, he was eager to see whether abuse in prisons can be explained by the inherent psychological traits of both guards and prisoners. Given the topic, he received funding from the U.S. Office of Naval Research. Funding in hand, Zimbrano set about recruiting participants. This turned out to be no problem at all, as a number of Stanford students volunteered to take part. Zimbrano then appointed some of the volunteers as guards and the others were designated as prisoners. The experiment could begin.

In the basement of the university’s psychology department, Zimbrano had built a makeshift ‘prison’. In all, 12 prisoners were kept here in small cells, while 12 guards were assigned a different part of the basement. While the prisoners had to endure tough conditions, the guards enjoyed comfortable, furnished quarters. The participants were also dressed for their parts, with the guards given uniforms and wooden batons. They were also kitted out with dark sunglasses so they could avoid eye contact with the people they were tasked with guarding.

Within 24 hours, any semblance of calm had gone. The prisoners started to revolt and the guards started to react. Special cells were set up to give well-behaving prisoners preferential treatment. The guards – who were barred from actually physically hitting their charges – started to use psychological methods to keep prisoners down. They would deny them food or put prisoners in darkened cells. Sleep was also denied to the prisoners. Within six days, Zimbrano agreed to halt the experiment. He did, at least, have more than enough evidence – some of it filmed – to draw on when making his conclusions.

Professor Zimbrano noted that around one third of the guards – again, young men taken randomly from the Stanford student population – exhibited genuine sadistic tendencies. At the same time, most of the inmates were seen to ‘internalise’ their roles. They took on the mentality of prisoners. While they could have left at any time, they instead gave up and became weak and passive. In the end, the experiment received, and continues to receive, criticism for the harsh methods used. Nevertheless, the findings of the Stanford Prison Experiment actually changed the way U.S. prisons are run and they are often held up as proof that most people can inflict cruelty and suffering on another human being if they are given a position of power and ordered to do so.

The 10 Cruelest Human Experimentation Cases in History
In apartheid South Africa, soldiers were subjected to electroshock therapy to try and ‘cure’ homosexuality. Encyclopedia of Mental Disorders.

The South African ‘Aversion Project’

In Apartheid-era South Africa, national service was compulsory for all white males. At the same time, homosexuality was classed as a crime. Inevitably, therefore, any gay men who found themselves called into service were in for a tough time. But it wasn’t just name-calling or casual discrimination they had to contend with. Many were subjected to cruel experiments. The so-called ‘Aversion Project’, run throughout the 1970s and then the 1980s, was aimed at ‘treating’ homosexuals. As well as psychological treatments, it also used physical ‘treatments’, many of which would rightly be regarded as torture.

The project first really got started in 1969, with the creation of Ward 22. The creepily-named ward was part of a larger military hospital just outside of Pretoria and was designed to treat mentally-ill soldiers. For the unit chief Dr Aubrey Levin, this including homosexuals, regarded as unstable, or even ‘deviants’. For the most part, the doctor was determined to prove that electric shock therapy and conditioning could ‘cure’ the patients of their desires. Hundreds of men were electrocuted, often while being forced to look at pictures of gay men. The electric current would then be turned off and pictures of naked women shown instead in the hope that this would alter the mindset.

Inmates subjected to such experimental treatment would sometimes be tested, given temptations to see if they really were ‘cured’. Persistent ‘offenders’ were given hormone treatments, almost always against their will, and many were even chemically castrated. Even by the middle of the 1970s, when numerous, more ethical, studies had proven that ‘conversion therapies’ could change a person’s sexuality, Ward 22 carried on with its work. In fact, in only ended with the fall of the apartheid regime. To the very end of the project, Dr Levin maintained that all the men he treated were volunteers and asked for his help. Many of his peers disagreed, as did a judge, who sentenced him to five years in prison in 2014.

The 10 Cruelest Human Experimentation Cases in History
The people of the Marshall Islands got radiation sickness – while American scientists watched on. The Lincoln Center.

Project 4.1

On March 1, 1954, the United States carried out Castle Bravo, testing a nuclear bomb on the Bikini Atoll, in the middle of the Pacific Ocean. The test not only went without a hitch, it actually went better than expected. The yield produced by the bomb was much higher than scientists had anticipated. At the same time, the weather conditions in this part of the Pacific turned out to be different to what had been predicted. Radiation fallout from the blast was blown upwind, towards the Marshall Islands. But, instead of alerting the islanders to the danger, the project heads sensed an opportunity. How many times would they be able to see the affect of radiation fallout on a population for real?

Making the most of the opportunity, the American scientists simply sat back an observed. That is, they watched innocent people be affected by the fallout of an American nuclear bomb. Over the next decade, the project observers noted an upturn in the number of women on the Marshall Islands suffering miscarriages or stillbirths. But then, after ten years or so, this spike ended. Things seemingly returned to normal, and so scientists were unable – or unwilling – to make any formal conclusions. But then, things started to go downhill again.

At first, children on the Marshall Islands were observed to be growing less than would be expected. But then, it became clear that not only were they suffering from stunted growth, but a higher-than-expected proportion of youngsters were developing thyroid cancer. What’s more, by 1974, the data was showing that one in three islanders had developed at least one tumor. Later analysis, published in 2010, estimated that around half of all cancer cases recorded on the Marshall Islands could be attributed to the 1954 nuclear test, even if people never displayed any obvious signs of radiation poisoning in the immediate aftermath of the explosion.

Given that the initial findings of Project 4.1 as it was known were published in professional medical journals as early as 1955, the American government has never really denied that the experiment took place. Rather, what has been, and continues to be contested, is whether the U.S. actually knew that the islands would be affected before they carried out the test. Many on the Marshall Islands believe that Project 4.1 was premeditated, while the American authorities maintain that it was improvised in the wake of the explosion. The debate continues to rage.

The 10 Cruelest Human Experimentation Cases in History
Sharecroppers in Alabama were denied medicine as part of this cruel experiment. Encyclopedia Brittanica.

The Tuskegee Experiments

For four decades, African-American men in Macon County, Alabama, were told by medical researchers that they had ‘bad blood’. The scientists knew that this was a term used by sharecroppers in this part of the country to refer to a wide range of ailments. They knew, therefore, that they wouldn’t question the prognosis. And neither would they raise any concerns or questions when the same researchers gave them injections. Which is how doctors working on behalf of the U.S. Public Health Service (PHS) were able to look on as hundreds of men went mad, blind or even died as a result of untreated syphilis.

When the experiment began back in 1932, there was no known cure for syphilis. As such, PHS researchers were determined to make a breakthrough. They went to Tuskegee College in Alabama and enlisted their help. Together, they enlisted 622 African-American men, almost all of them very poor. Of these men, 431 had already contracted syphilis prior to 1932, with the remaining 169 free from the disease. The men were told that the experiment would last for just six years, during which time they would be provided with free meals and medical care as doctors observed the development of the disease.

In 1947, penicillin became the recommended treatment for syphilis. Surely the doctors would give this to the men participating in the Tuskegee Experiment? Not so. Even though they knew the men could be cured, the PHR workers only gave them placebos, including aspirin and even combinations of minerals. With their condition untreated, the men slowly succumbed to syphilis. Some went blind, others went insane, and some died within a few years. What’s more, in the years after 1947, 19 syphilitic children were born to men enrolled in the study.

It was only in the mid-1960s that concerns started to be raised about the morality of the experiment. San Francisco-based PHS researcher Peter Buxton learned about what was happening in Alabama and raised his concerns. However, his superiors were unresponsive. As a result, Buxton leaked the story to a journalist friend. The story broke in 1972. Unsurprisingly, the public were outraged. The experiment was halted immediately, and the Congress inquiries began soon after. The surviving participants, as well as the children of those men who had died, were awarded $10 million in an out-of-court settlement. Finally, in 1993, President Bill Clinton offered a formal and official apology on behalf of the U.S. government to everyone affected by the experiment.

The 10 Cruelest Human Experimentation Cases in History
During the infamous Project MK-Ultra, the CIA gave thousands of people LSD.

Project MK-Ultra

Though they had the Bomb, in the 1950s, the CIA were still determined to enjoy every advantage over their enemies. To achieve this, they were willing to think outside of the box. Perhaps the best example of this was MK-Ultra, a top-secret project where the CIA attempted to alter brain function and explore the possibility of mind control. While much of the written evidence, including files and witness testimonies, were destroyed soon after the experiments were brought to an end, we do know that the project involved a lot of drugs, some sex and countless instances of rule bending and breaking.

Project MK-Ultra was kick-started by the Office of Scientific Experiments at the start of the 1950s. Central to the project was determining how LSD affects the mind – and, more importantly, whether this could be turned to America’s advantage. In order to learn more, hundreds, perhaps even thousands of individuals, were given doses of the drug. In almost all cases, they were given LSD without their explicit knowledge or consent. For example, during Operation Midnight Climax in the early 1960s, the CIA opened up brothels. Here, the male clients were dosed up with LSD and then observed by scientists through one-way mirrors.

The experiments also included subjecting American citizens to sleep deprivation and hypnosis. Not all of the tests went plainly. Several people died as a direct result of Project MK-Ultra, including a US Army biochemist by the name of Frank Olsen. In 1953, the scientist was given a dose of LSD without his knowledge and, just a week later, died after jumping out of a window. While the official reason of his death was recorded as suicide, Olsen’s family have always maintained that he was effectively killed by the CIA.

When President Gerald Ford launched a special Commission on CIA activities in the United States, the work of Project MK-Ultra came to light. Two years previously, however, the-then Director of the CIA, Richard Helms, had ordered all files relating to the experiments to be destroyed. Witness testaments show that around 80 institutions were involved in the experiments, with thousands of people given hallucinogenic drugs, usually by CIA officers with no medical background. And so, in the end, was it all worth it? The CIA has acknowledged that the experiments produced nothing of real, scientific value. Project MK-Ultra has, however, lived on in the popular imagination and has inspired numerous books, video games and movies.

The 10 Cruelest Human Experimentation Cases in History
Soldiers, orphans and prisoners were all infected with syphilis in 1940s Guatemala.

Guatemalan Syphilis Experiment

For more than two years in the middle of the 20th century, the United States worked directly with the health ministries of Guatemala to infect thousands of people with a range of sexually transmitted diseases, above all syphilis. Since they wanted to do this without the study subjects knowing about it – after all, who would give their consent to being injected with syphilis? – it was decided that the experiment should take place in Guatemala, with soldiers and the most vulnerable members of society to serve as the guinea pigs.

The Guatemalan Syphilis Experiment (it was not given an official codename or even a formal project title) began in 1946. It was headed up by John Charles Cutler of the US Public Health Service (PHS). Despite being a physician himself, Cutler was happy to overlook the principle of ‘First, do no harm’ in order to carry out his work. Making use of local health clinics, he tasked his staff with infecting around 5,500 subjects. Most of them were soldiers or prisoners, though mental health patients and prostitutes were also used to see how syphilis and other diseases affect the body. Children living in orphanages were even used for the experiments.

In all cases, the subjects were told they were getting medication that was good for them. And, while all subjects were given antibiotics, an estimated 83 people died. In 1948, with the wider medical community hearing rumors of what was being done in Central America, and with the American government wary of the potential fallout, the experiments were brought to an abrupt end. Cutler would go on to carry out similar experiments in Alabama, though even here he stopped short of actually infecting his subjects with life-threatening diseases.

It was only in 2010, however, that the United States government issued a formal apology to Guatemala for the experiments it carried out in the 1940s. What’s more, President Barack Obama called the project “a crime against humanity”. That didn’t mean that the victims could get compensation, however. In 2011, several cases were put forward but then rejected, with the presiding judge noting that the U.S. government could not be held liable for actions carried out in its name outside of the country. A $1 billion lawsuit against the John Hopkins University and against the Rockefeller Foundation is still open.


The 10 Cruelest Human Experimentation Cases in History
During the Holocaust, twins were specially selected for sick experiments. Yad Vashem.

Mengele’s Twins

A world at war gave the Nazi regime the ideal cover under which they would carry out some of the most horrific human experiments imaginable. At Auschwitz concentration camp, Dr Josef Mengele made full use of the tens of thousands of prisoners available to him. He would carry out unnecessarily cruel and unusual experiments, often with little or no scientific merit. And, above all, he was fascinated with twins. Or, more precisely, with identical twins. These would be the subjects of his most gruesome experiments.

Mengele would personally select prospective subjects from the ramps leading off the transport trains at the entrance to the concentration camp. Initially, his chosen twins were provided with relatively comfortable accommodation, as well as more generous rations than the rest of the inmate population. However, this was just a temporary respite. Mengele’s experiments were as varied as they were horrific. He would amputate one twin’s limbs and then compare the growth of both over the following days. Or he would infect one twin with a disease like typhoid. When they died, he would kill the healthy twin, too, and then compare their bodies.

Gruesomely, the records show that on one particularly bloody night, Mengele injected chloroform directly into the heart of 14 sets of twins. All died almost immediately. Another infamous tale tells of Mengele trying to create his own conjoined twins: he simply stitched two young Romani children back-to-back. They both died of gangrene after several long and painful days. Mengele also had a team of assistants working for him, and they were no less cruel.

Nobody will ever know just how many children or adults were victims of Mengele’s experiments. Despite being meticulous record keepers, the Nazis kept some things secret. Tragically for his victims and their relatives, Mengele never faced justice for his actions. He was smuggled out of Europe by Nazi sympathisers at the end of the war and lived for another 30 years, in hiding, in South America.


Where did we find this stuff? Here are our sources:

“Unmasking Horror: A special report.; Japan Confronting Gruesome War Atrocity”. Nicholas D. Kristof, The New York Times, 1995.

“Little Albert regains his identity”. American Psychology Association, 2010.

“Unit 731: Japan discloses details of notorious chemical warfare division”. Justin McCurry, The Guardian, April 2018.