From the CIA’s secret mind control program, MK Ultra, to the stuttering “Monster” study, American researchers have a long history of engaging in human experiments. The studies have helped us better understand ourselves and why we do certain things.

These four experiments did just this and helped us better understand human behavior. However, some of them would be considered unethical today due to either lack of informed consent or the mental and/or emotional damage they caused.

1. Cognitive Dissonance Experiment

After proposing the concept of cognitive dissonance, psychologist Leon Festinger created an experiment to test his theory that was also known as the boring experiment. 

Participants were paid either $1 or $20 to engage in mundane tasks, including turning pegs on a board and moving spools on and off a tray. Despite the boring nature of the activities, they were asked to tell the next participant that it was interesting and fun.

The people who were paid $20 felt more justified lying to others because they were better compensated — and they experienced less cognitive dissonance. Participants who were paid $1 felt greater cognitive dissonance due to their inability to rationalize lying.

In an attempt to reconcile their dissonance, they convinced themselves that the tasks were actually enjoyable.

2. The Little Albert Experiment 

In 1920, psychologist John. B. Watson and graduate student (and future wife) Rosalie Rayner wanted to see if they could produce a response in humans using classical conditioning — the way Pavlov did with dogs.  

They decided to expose a 9-month-old baby, whom they called Albert, to a white rat. At first, the baby displayed no fear and played with the rat. To startle Albert, Watson and Rayner would then make a loud noise by hitting a steel bar with a hammer. 

Each time they made the loud sound while Albert was playing with the rat, he became frightened, started crying, and crawled away from the rat. He had become classically conditioned to fear the rat because he associated it with something negative. He then developed stimulus generalization, where he feared other furry white objects — including a rabbit, white coat, and a Santa mask. 

3. Stanford Prison Experiment

In 1971, Stanford psychologist Philip Zimbardo designed a study to examine societal roles and situational power — through an experiment that recreated prison conditions. 

Zimbardo created a mock prison in a building on Stanford’s campus. He assigned study participants to be either guards or prisoners. Prisoners were given numbers instead of names, had a chain attached to one leg, and were dressed in smocks and stocking caps.

Those assigned to the role of a guard quickly conformed to their new position of power. They became hostile and aggressive toward the prisoners, subjecting them to psychological and verbal abuse — despite never having previously demonstrated such attitudes or behavior. The experiment was slated to last two weeks but needed to be ended after only six days. 

4. The Facial Expression Experiment

In 1924, psychology graduate student Carney Landis wanted to study how people’s emotions were reflected in their facial expressions, exploring whether certain emotions caused the same facial expressions in everyone.

Landis marked participants’ faces with black lines to study the movement of their facial muscles as they reacted. At first, he had them do innocuous tasks, such as listening to jazz music or smelling ammonia. 

As Landis grew frustrated that their responses weren’t strong enough, he had participants engage in increasingly shocking acts, such as sticking their hands into a bucket with live frogs in it. Eventually, Landis instructed participants to decapitate a live mouse. If they refused, he decapitated the mouse himself to elicit a strong reaction from them.

Read More: 5 Unethical Medical Experiments Brought Out of the Shadows of History

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Allison Futterman is a Charlotte, N.C.-based writer whose science, history, and medical/health writing has appeared on a variety of platforms and in regional and national publications. These include Charlotte, People, Our State, and Philanthropy magazines, among others. She has a BA in communications and a MS in criminal justice.