Curiosity is the fuel that drives social experiments performed in the world of science. Today, experiments must abide by the American Psychological Association’s (APA) Code of Conduct, which pertains to everything from confidentiality, to consent, to overall beneficence. However, the standards weren’t always so high. In their latest video, “10 Evil Social Experiments,” Alltime10s highlights the most famous and disturbing experiments that took place all around the world that could never happen today.

Adults, children, and even animals were a part of the inhumane practices of several mad scientists. In 1939, psychologist Wendell Johnson at the University of Iowa performed "The Monster Study," a stuttering experiment on 22 orphaned children. The children were divided into two groups. The first received positive speech therapy, in which the children's successes were praised. The other group had negative therapy and were told off for every mistake they made.

The effects on the children who had negative speech therapy were horrible. Their schoolwork suffered, their behavior became more timid, and they developed speech impediments. In 2007, six of the children were awarded $925,000 for life-long psychological damage.

In the 1970s to 1980s, during the Apartheid era, the South African army forced suspected gay and lesbian soldiers to undergo sex-change operations, chemical castrations, electrical shocks, and other forms of unethical medication, in an attempt to cure their illegal sexuality, which became known as “The Aversion Project.”

Inevitably, this became psychologically damaging to about 900 individuals who underwent reassignment operations carried out in military hospitals in South Africa throughout this period. The patients were abandoned, and often unable to pay for the hormones needed to maintain their new identity, leading some to commit suicide.

Animals could not escape the wrath of mad scientist Dr. Harry Harlow in his experiment “The Pit of Despair.” Harlow experimented on baby rhesus monkeys to study social interaction and isolation in the 1970s. He would select baby monkeys who had bonded with their mother and separate them, placing the infants in little steel chambers with no contact with anything else. He kept them in there for up to a year, causing irreparable psychosis in many of the monkeys.

The monkeys were later returned to a group, but were bullied; others starved themselves to death. When the test subjects later became mothers, they would chew off the fingers of their offspring or crush their heads. Not only were Harlow’s experiments extreme, they revealed nothing new about social interactions.

Luckily, the APA's Code of Conduct brought ethics in psychological experiments. Review boards enforce these ethics to prevent experiments like the ones listed above from occurring.

View the rest of Alltime10s video to see the most disturbing social experiment in the 20th century.