The 9 Most Brutal Psychological Experiments in History (10 photos)

What happens if you spend half a boy's childhood convincing him he's a girl? What if you torture someone with electric shocks or force a test subject to decapitate a live rat? Here are nine of the most brutal and pointless psychological experiments in human history.







1. Raising a Boy as a Girl (1965–2004)

Following a botched circumcision at eight months old, Bruce Reimer lost his penis. Psychologist John Money of Johns Hopkins University in Baltimore advised the parents to raise the boy as a girl. Bruce became Brenda, and Money treated the child's life as a fascinating case study. On the surface, the transition seemed successful—until his parents finally revealed the truth. The revelation shattered Bruce's life, leading to three suicide attempts. Seeking a fresh start, he reclaimed his male identity, changed his name, and eventually married. Tragically, after a painful divorce, he took his own life at the age of 38.





2. The Pit of Despair (1960s)

Fortunately, Dr. Harry Harlow confined his experiments to monkeys. He separated infant rhesus macaques from their mothers and isolated them in dark chambers for up to a year. Upon reunion, the young monkeys exhibited severe psychological disturbances. Of course, proving the obvious point—that depriving a baby of maternal warmth causes deep psychological damage—hardly required such profound cruelty.



3. The Milgram Experiment (1974)

The study involved an experimenter, a genuine participant (the "teacher"), and an actor playing a second participant (the "learner"). The teacher was told the study aimed to test memory and learning techniques. However, the routine memory test quickly turned into torture: for every wrong answer, the teacher had to administer an electric shock to the learner. While no real shocks were delivered, the voltage dial advanced by 15 volts with each mistake. Whenever the teacher hesitated, the experimenter pressured them to continue for the sake of science. The results were chilling: 65% of participants delivered the maximum 450-volt shock. Milgram proved that ordinary people, under the influence of authority, are capable of inflicting extreme harm—actions they would never consider in everyday life.



4. Learned Helplessness (1966)

Psychologists Martin Seligman and Steven Maier split dogs into three groups. The first group received no shocks. The second group received shocks that they could stop by pressing a lever. The third group was the unluckiest: they received unavoidable shocks. Later, when the third group was placed in open cages where they could easily escape the shocks, none of the dogs even tried to press the lever or run. They had resigned themselves to suffering as something inevitable.



5. The Monster Study (1939)

In 1939, Wendell Johnson and graduate student Mary Tudor at the University of Iowa recruited 22 orphaned children from Davenport. They split the children into two groups: one received positive reinforcement praising their speech, while the other was relentlessly criticized and told they stuttered terribly. In reality, all the children originally spoke normally. As a result of the constant belittling, many children in the second group developed severe, lifelong speech impediments and psychological issues.



6. Little Albert (1920)

Over two months, nine-month-old "Little Albert" was exposed to a tame white rat, cotton wool, a Santa Claus mask with a beard, a white rabbit, and other fuzzy objects. Initially, he showed no fear. Then, psychologist John B. Watson began striking a steel bar with a hammer behind the infant every time Albert touched the rat. Consequently, the child developed an intense terror not only of the rat, but of anything soft and white, including cotton, Santa's beard, and rabbits. The conditioning left him permanently traumatized.



7. Carney Landis's Facial Expression Experiment (1924)

In 1924, Carney Landis of the University of Minnesota conducted a study to see if human emotions trigger universal facial expressions. He subjected his student participants to strong emotional stimuli: making them smell ammonia, listen to jazz, watch pornography, and reach into buckets full of live frogs, photographing their expressions throughout.

The climax of the experiment came when Landis ordered the students to decapitate a live rat. Surprisingly, most complied without question. While Landis failed to find any consistent facial expressions, he reached a chilling conclusion: people in a research setting are disturbingly willing to obey authority, no matter how extreme the demand.



8. Drug Self-Administration Experiments on Monkeys (1969)

A group of monkeys was trained to self-administer various addictive drugs. The results were horrific: monkeys given cocaine suffered severe convulsions and hallucinations, eventually tearing off their own fingers. Those given amphetamines plucked out all their fur, while animals given a combination of cocaine and morphine died within two weeks of starting the experiment.



9. The Stanford Prison Experiment (1971)

Psychologist Philip Zimbardo set up a mock prison in the basement of Stanford's psychology building and assigned 24 male student volunteers to play the roles of either "guards" or "prisoners."

The participants were initially hesitant, but by the second day, chaos erupted: the "guards" brutally crushed a rebellion staged by the "prisoners."

The guards quickly instituted cruel enforcement measures, denying prisoners privacy even during bathroom breaks. When asked their names, many prisoners began identifying themselves solely by their assigned numbers. The "inmates" fully internalized their role as captive subjects, while the "guards" exhibited genuine sadistic behavior toward peers who had been their friendly classmates just days earlier.

Originally scheduled to last two weeks, the experiment had to be shut down prematurely due to ethical concerns.