20 Weirdest Experiments Ever Conducted on Humans
This is a chilling journey through history’s most bizarre and unethical human experiments, revealing the dark side of scientific curiosity and the haunting consequences of pushing ethical boundaries.
- Alyana Aguja
- 6 min read
Over the course of history, science has ventured across disturbing boundaries, performing strange and frequently immoral experiments on unsuspecting human beings in the pursuit of knowledge. From mind-control experiments and sleep deprivation to covert drug testing and shocking behavioral experiments, these actual experiments reveal the shadowy side of human curiosity. This is a riveting examination of how far scientists have proceeded—and the eerie repercussions that still resonate today.
1. The Monster Study (1939)
Image from CBS News
Researchers at the University of Iowa sought to know the impact of positive and negative speech therapy on children. Sadly, they used orphans for negative reinforcement in a cruel manner, leaving some with speech problems for the rest of their lives. The term “Monster Study” was coined by the researchers’ guilt over their unethical method.
2. The Milgram Obedience Experiment (1961)
Image from Wikipedia
Stanley Milgram experimented with how far individuals would go in following orders, even if it meant hurting others. Participants were told to administer electric shocks to an individual (an actor) for incorrect responses, with the shocks getting stronger. Many persisted despite screams, exposing ugly realities about human obedience.
3. The Stanford Prison Experiment (1971)
Image from BBC
Psychologist Philip Zimbardo created a mock prison setting with volunteers who were either “guards” or “prisoners.” The guards rapidly became cruel, and the prisoners were compliant, so the experiment had to be stopped after only six days. It demonstrated how quickly power can corrupt behavior.
4. David Reimer – The John/Joan Case (1965)
Image from Quillette
Following a failed circumcision, psychologist John Money recommended that David Reimer be raised as a female to experiment with gender identity theories. The experiment was a tragedy, as Reimer had difficulty with his identity and ultimately committed suicide. It is still a cautionary tale of unethical medical experimentation.
5. Little Albert Experiment (1920)
Image from Wikipedia
John B. Watson and Rosalie Rayner conditioned a baby, “Albert,” to be afraid of a white rat by associating it with loud, scary sounds. Albert soon became afraid of anything fluffy and white. The experiment proved classical conditioning but was severely criticized on ethical grounds.
6. Unit 731 (1930s-1945)
Image from The Guardian
Japanese scientists in WWII subjected Chinese civilians and prisoners of war to inhuman experiments—some of these involved vivisection without anesthetics, tests of biological warfare, and frostbite. The brutality was such that many records were later obliterated to keep the horrors in secret.
7. The Aversion Project (1970s-1980s)
Image from LinkedIn
Under apartheid South Africa, the military forced gay conscripts to undergo “conversion therapy” through chemical castration and electroshock. Some were even forced to undergo sex reassignment surgery. Thousands were subjected to these dehumanizing experiments under the guise of “curing” homosexuality.
8. MKUltra (1950s-1970s)
Image from The HISTORY Channel
The CIA secretly tested LSD, hypnosis, and mind control methods on unsuspecting subjects. Several of the test subjects suffered severe psychological damage, with accounts of fatalities and mental collapse. Details of the project only came to light decades later, revealing government excess at its worst.
9. Sleep Deprivation Experiments (1960s)
Image from NPR
Randy Gardner, a teenager, went 11 days without sleep to learn about the consequences of sleep deprivation. He developed hallucinations, forgot things, and became paranoid, but recovered without harm. This experiment is still one of the most drastic experiments on human endurance.
10. The Robbers Cave Experiment (1954)
Image from The Guardian
Researchers examined intergroup conflict by pitting two groups of boys against one another at a summer camp. The boys rapidly established hostile rivalries, but researchers later brought them together by instituting common challenges. The study provided insight into group dynamics and conflict resolution.
11. The Landis Facial Expression Experiment (1924)
Image from University of York
The subjects were instructed to copy certain facial expressions while viewing gruesome stimuli—including being instructed to behead a live rat. The majority of the subjects followed instructions, demonstrating how individuals react to authority. It’s psychology’s most contentious and strange experiment.
12. Operation Midnight Climax (1950s-60s)
Image from The HISTORY Channel
The CIA established safe houses where prostitutes tempted men, and they were unwittingly given LSD. Agents monitored the effects through two-way mirrors to observe behaviors. The combination of espionage, drugs, and voyeurism makes it one of the most bizarre covert operations in history.
13. The Good Samaritan Experiment (1973)
Image from Stanford SPARQ - Stanford University
Scientists tried to see if seminarians would pause to assist a person in need under the pressure of time. Ironically, most did not stop for a person in need—even while about to give a lecture on the Good Samaritan. It revealed the subtleties of human behavior and moral choice.
14. The Third Wave (1967)
Image from RANDOM Times
A California high school teacher created a simulated fascist movement to show how easily people fall into authoritarianism. Within days, students embraced strict discipline and exclusionary behavior. The experiment spiraled so intensely that it had to be abruptly stopped.
15. The Tearoom Trade Study (1970)
Image from Salon für Kunstbuch
Sociologist Laud Humphreys secretly watched men having anonymous sex in public toilets. He later followed them under false pretenses to observe their home lives. Although it yielded seminal data, it involved serious ethical issues regarding privacy.
16. Monkey Drug Trials (1969)
Image from JAMA Network
Monkeys were conditioned to administer drugs such as cocaine, morphine, and amphetamines themselves to learn about addiction. The outcomes were appalling—some overdosed, mutilated themselves, or perished. Although a shock, the experiment highlighted the risks of unsupervised use of drugs.
17. The Rosenhan Experiment (1973)
Image from New Scientist
Psychiatrist David Rosenhan sent healthy “pseudo-patients” to the psychiatric wards, telling them they experienced hearing voices. They were all accepted, and their normal acts were diagnosed as pathological. The experiment uncovered sobering defects in psychiatric diagnoses.
18. Operation Sea-Spray (1950)
Image from Working Class History
The U.S. Navy secretly sprayed the San Francisco Bay Area with a bacterium known as Serratia marcescens to determine biological warfare vulnerabilities. Numerous residents became ill, and one person died, although the cause was not initially associated with the test. The public did not learn the truth until years later.
19. The Human Radiation Experiments (1940s-1970s)
Image from Atomic Heritage Foundation
The U.S. government exposed unwitting individuals to radiation to study its effects, including injecting plutonium into patients. Some suffered severe health problems and died from the exposure. The scandal only came to light decades later, sparking outrage over ethical breaches.
20. The Doppelgänger Twin Study (1960s)
Image from Slate Magazine
In a secret adoption experiment, identical twins were separated at birth and placed into different families to observe how the environment shapes identity. None of the twins knew about their siblings until adulthood. The experiment caused deep emotional trauma when the truth surfaced.