The field of psychology has always fascinated people. Not only has it raised curiosity among common men, but many well-known experts throughout history have also shown a keen interest in studying psychology to understand human nature. Their interest in studying complex human behavioral patterns and the reason behind it encouraged them to come up with their own theories and experiments that challenge our conventional wisdom and understanding of the human mind and actions.

Following are 10 such most influential psychological experiments in history that reveal astonishing facts about human nature:

A Class Divided Experiment

An interesting study was conducted by Ms. Jane Elliott in 1968 to discuss the issues of racism, discrimination, and prejudice with her third-grade students of Riceville, Lowa classroom. The experiment was inspired by the killing of civil rights leader Dr. Martin Luther King Jr. and the great work he did during his political career to promote equal rights for all.

Ms. Elliott divided the class into 2 groups: Blue-eyed students, which was labeled as a superior group and Brown-eyed students, which was labeled as inferior or minority group. Since Blue-eyed students were given preferential treatment and had special privileges over brown-eyed students, they were discouraged to talk to the minority group and they were also individually asked to discuss negative characteristics of the minority group.

To the surprise of Ms. Elliott, the behavior of students changed almost immediately. While the blue-eyed group’s academic performance was better due to high self-esteem, the brown-eyed group had worse academic performance because of lowered self-esteem. They experienced lower confidence as they were constantly bullied by the superior group. The roles were reversed the next day and a similar outcome was observed.  When the experiment ended, the students learned an important lesson of equality.

Asch Conformity Study

The study was conducted by Dr. Solomon Asch at Swarthmore College, Pennsylvania in 1951. The aim of the experiment was to evaluate how a person’s beliefs and opinions are influenced by a majority group.

The experimenter showed participants a picture of numbered lines of varying lengths and asked them to identify the longest line. The catch was that out of all those participants, only one was a true participant while the rest of them were actors who were told to give wrong, erroneous answers. Surprisingly, the true participants agreed with the answers of the actors, despite the realization that they were wrong.

After all, it wasn’t very difficult to recognize the longest line. Following the experiment when they were interviewed, most true participants agreed that they knew they were wrong, but chose to go with the group out of fear of being mocked.

The study concluded that people chose to go along with the majority as they want to fit in the group, and least care about being right.


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Kitty Genovese Case

While it was not actually a self-constructed experiment to make any findings, Kitty Genovese murder case ended up providing a fascinating and shocking truth about human psychology.

The case happened in New York City in 1964 when Kitty Genovese, a 28-year old was stabbed and murdered in front of almost 40 neighbors, but none of them reached for help or even called police.

The situation gave birth to a psychological theory named “Bystander effect”, which states that individuals are less likely to extend help to a victim when other bystanders are present. In fact, the greater the number of bystanders, the less likely it is that anyone will come for help.

Stanford Prison Experiment

One of the most influential psychological experiments in history, Stanford Prison Experiment shows how people can easily adapt to certain roles under the right situation, and of course, it also displays the worse of human nature. The study was conducted by a Psychology Professor Philip Zimbardo in 1971 at Stanford University to study how well humans can keep their roles under a made-up situation.

College students were enrolled to play the role of “guards” and “prisoners” in a contrived prison environment which looked absolutely realistic. While the prison guards were instructed not to physically abuse any of the prisoners, shockingly, within a few hours of the beginning of the experiment, they started to harass prisoners. They taunted them, insulted them and gave them difficult tasks to achieve.

As the days passed, guards became sadistic and they started using all the means to break down prisoners both physically and mentally. The situation went so worse that the experiment was called off early because participants started showing troubling mental signs.

The study concluded that people conform to the social roles assigned to them even if their individual personality is different.

Hawthorne Effect Experiment

The experiment was conducted by Henry A. Landsberger at Hawthorne Works in Chicago, Illinois in the year 1955. While the aim of the experiment was to study the effects of physical conditions on productivity, the study took a turn and concluded that human behavior changes when they are under observation or being studied.

The company actually conducted the study to evaluate if changing the lighting in the building affects the productivity of workers. They found that whenever lighting was changed from low intensity to high intensity, workers increased their productivity. They got the same outcome even if they changed the lighting from high intensity to low intensity. This concluded that the increase in productivity was not due to change in lighting, but workers showed higher efficiency because they were aware of the fact that they were under observation.

The Marshmallow Test

The experiment was conducted by Psychologist Walter Mischel in 1972 at Stanford University for studying deferred gratification in 600 children and how it impacts their future success.

The children aged 4 to 6 years were led into a room where a marshmallow, or sometimes pretzel or cookie, were placed on a table in front of them. The experimenter said to the children that they would receive another marshmallow as a prize if the first marshmallow was still on the table after they return to the room after 15 minutes.  The experimenter recorded the outcomes. It was found that only a minority of children ate the marshmallow immediately, while one-third delayed gratification and managed to receive the second marshmallow. The experiment also concluded that age was a major determinant factor of delayed gratification.

In follow-up studies, it was found that children who showed deferred gratification had better life outcomes. They were significantly more competent and received higher SAT scores than their peers who were not able to wait long enough.

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Little Albert Experiment

This experiment, which was conducted by John Watson and Rosalie Rayner at Johns Hopkins University in 1920, concluded that the irrational fears of certain things that we develop during our life are often related to our childhood experiences.

A white rat was presented in front of a 9-month old baby, who was not scared of animals before. Each time Albert touched the rat, the experimenters produced a loud sound behind his back using a suspended steel bar and a hammer. Thus, a fear was produced in the baby’s mind and every time a rat was introduced in the room, the baby started to cry. The experiment was repeated with other animals and things as well with the same outcome – Albert started fearing them all.

Bobo Doll Experiment

The study was conducted by Dr. Alburt Bandura, an American-Canadian Psychologist, at Stanford University between 1961-1963. He conducted this experiment to prove that human behavior is learned through social imitation, rather than inherited genetic factors.

The participants were children who were divided into 3 groups – one group was shown a video of an adult showing aggressive behavior towards a Bobo doll; another group was shown a video of a passive adult playing with the Bobo doll, and the third group had no exposure to adult at all. After showing videos to them, children were sent to another room with the same Bobo doll.

It was found that the children who were exposed to adult with aggressive behavior showed similar aggressiveness towards the doll, while others were found to be less aggressive. The study also found that boys who were shown the video of aggressive male models showed more aggression than boys that were shown the videos of aggressive female models. This further concluded that children are more influenced by the same sex and try to imitate their behavior more.

Robbers Cave Experiment

The experiment, which aimed to study group conflict, was conducted by Muzafer and Carolyn Sherif in 1954 at the University of Oklahoma. This is an ideal example of human behaviors that demonstrate that negative attitudes can arise due to competition when the resources are limited.

Twenty-Two Boys of 11 or 12 years of age were divided into 2 groups and taken to an isolated area, in the name of a summer camp. Both these groups were not allowed to meet each other for at least one week. The boys befriended with their peers of the same group, and after one week when they were allowed to meet with another group, they showed signs of hostility and prejudice towards them. A series of competitions were also conducted by experimenters to increase the feeling of hostility.  This resulted in further competitiveness and both the groups even denied to eat in the same hall.

Finally, the experimenters decided to end the conflict and conducted fun activities to turn rivalry into friendship. Finally, everything went ok, concluding that any conflict or prejudice can simply be resolved through cooperation.

The Invisible Gorilla Experiment

The experiment was conducted by Daniel Simons and Christopher Chabris in the year 1999 at Harvard University.

When participants were asked to count the number of basketball passes in a video, they failed to notice that there was also a gorilla in the video. The pace of the video was moderate so it was easy for the participants to count the passes, but they still failed to notice gorilla that walked silently into the court and stood there for a few seconds before moving out of the camera.

This study gave us an interesting fact about selective attention psychology; it demonstrated that when people are asked to attend to one task, they often overestimate their multitasking ability and begin to focus on that particular task so strongly that they may fail to notice other important details.

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