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The 25 Most Influential Psychological
Experiments in History
By Kristen Fescoe Published January 2016
The field of psychology is a very broad field comprised of many smaller specialty areas. Each of these specialty areas has been strengthened over the years by research studies designed to prove or disprove theories and hypotheses that pique the interests of psychologists throughout the world.
While each year thousands and thousands of studies are completed in the many specialty areas of psychology, there are a handful that, over the years, have had a lasting impact in the psychological community as a whole. Some of these were dutifully conducted, keeping within the confines of ethical and practical guidelines. Others pushed the boundaries of the field and created controversies that still linger to this day. And still others were not designed to be true psychological experiments, but ended up as beacons to the psychological community in proving or disproving theories.
This is a list of the 25 most influential psychological experiments still being taught to psychology students of today.
1. A Class Divided
Study Conducted By: Jane Elliott
Study Conducted in 1968 in an Iowa classroom
Experiment Details: Jane Elliott’s famous experiment was inspired by the assassination of Dr. Martin Luther King Jr. and the inspirational life that he led. The third grade teacher developed an exercise to help her Caucasian students understand the effects of racism and prejudice.
Elliott divided her class into two separate groups: blue-eyed students and brown-eyed students. On the first day, she labeled the blue-eyed group as the superior group and from that point forward they had extra privileges, leaving the brown-eyed children to represent the minority group. She discouraged the groups from interacting and singled out individual students to stress the negative characteristics of the children in the minority group. What this exercise showed was that the children’s behavior changed almost instantaneously. The group of blue-eyed students performed better academically and even began bullying their brown-eyed classmates. The brown-eyed group experienced lower self-confidence and worse academic performance. The next day, she reversed the roles of the two groups and the blue-eyed students became the minority group.
At the end of the experiment, the children were so relieved that they were reported to have embraced one another and agreed that people should not be
situations and it showed that people often care more about being the same as others than they do about being right.
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3. Bobo Doll Experiment
Study Conducted by: Dr. Alburt Bandura
Study Conducted between 1961-1963 at Stanford University
Experiment Details: During the early 1960s a great debate began regarding the ways in which genetics, environmental factors, and social learning shaped a child’s development. This debate still lingers and is commonly referred to as the Nature vs. Nurture Debate. Albert Bandura conducted the Bobo Doll Experiment to prove that human behavior is largely based upon social imitation rather than inherited genetic factors.
In his groundbreaking study he separated participants into three groups: one was exposed to a video of an adult showing aggressive behavior towards a
Bobo doll; another was exposed to video of a passive adult playing with the Bobo doll; and the third formed a control group. Children watched their assigned video and then were sent to a room with the same doll they had seen in the video (with the exception of those in the control group). What the researcher found was that children exposed to the aggressive model were more likely to exhibit aggressive behavior towards the doll themselves, while the other groups showed little imitative aggressive behavior. For those children exposed to the aggressive model, the number of derivative physical aggressions shown by the boys was 38.2 and 12.7 for the girls.
The study also showed that boys exhibited more aggression when exposed to aggressive male models than boys exposed to aggressive female models. When exposed to aggressive male models, the number of aggressive instances exhibited by boys averaged 104 compared to 48.4 aggressive instances exhibited by boys who were exposed to aggressive female models. While the results for the girls show similar findings, the results were less drastic. When exposed to aggressive female models, the number of aggressive instances exhibited by girls averaged 57.7 compared to 36.3 aggressive instances exhibited by girls who were exposed to aggressive male models. The results concerning gender differences strongly supported Bandura’s secondary prediction that children will be more strongly influenced by same-sex models.
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4. Car Crash Experiment
used in police interviews of eyewitnesses.
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5. Cognitive Dissonance Experiment
Study Conducted by: Leon Festinger and James Carlsmith
Study Conducted in 1957 at Stanford University
Experiment Details: The concept of cognitive dissonance refers to a situation involving conflicting attitudes, beliefs or behaviors. This conflict produces an inherent feeling of discomfort leading to a change in one of the attitudes, beliefs or behaviors to minimize or eliminate the discomfort and restore balance.
Cognitive dissonance was first investigated by Leon Festinger, after an observational study of a cult that believed that the earth was going to be destroyed by a flood. Out of this study was born an intriguing experiment conducted by Festinger and Carlsmith where participants were asked to perform a series of dull tasks (such as turning pegs in a peg board for an hour). Participant’s initial attitudes toward this task were highly negative. They were then paid either $1 or $20 to tell a participant waiting in the lobby
that the tasks were really interesting. Almost all of the participants agreed to walk into the waiting room and persuade the next participant that the boring experiment would be fun. When the participants were later asked to evaluate the experiment, the participants who were paid only $1 rated the tedious task as more fun and enjoyable than the participants who were paid $20 to lie. Being paid only $1 is not sufficient incentive for lying and so those who were paid $1 experienced dissonance. They could only overcome that dissonance by coming to believe that the tasks really were interesting and enjoyable. Being paid $20 provides a reason for turning pegs and there is therefore no dissonance.
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6. Fantz’s Looking Chamber
To test this concept, Fantz set up a display board with two pictures attached. On one was a bulls-eye and on the other was the sketch of a human face. This board was hung in a chamber where a baby could lie safely underneath and see both images. Then, from behind the board, invisible to the baby, he peeked through a hole to watch what the baby looked at. This study showed that a two-month old baby looked twice as much at the human face as it did at the bulls-eye. This suggests that human babies have some powers of pattern and form selection. Before this experiment it was thought that babies looked out onto a chaotic world of which they could make little sense.
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7. Hawthorne Effect
Study Conducted by: Henry A. Landsberger
Study Conducted in 1955 at Hawthorne Works in Chicago, Illinois
Experiment Details: The Hawthorne Effect came from a 1955 study
conducted by Henry Landsberger. This effect is a simple premise that human subjects in an experiment change their behavior simply because they are being studied.
Landsberger performed the study by analyzing data from experiments conducted between 1924 and 1932, by Elton Mayo, at the Hawthorne Works near Chicago. The company had commissioned studies to evaluate whether the level of light within a building changed the productivity of the workers. What Mayo found was that the level of light made no difference in productivity, as the workers increased their output whenever the amount of light was switched from a low level to a high level, or vice versa. The researchers noticed a tendency that the workers’ level of efficiency increased when any variable was manipulated. The study showed that the output changed simply because the workers were aware that they were under observation. The conclusion was that the workers felt important because they were pleased to be singled out, and increased productivity as a result. Being singled out was the factor dictating increased productivity, not the changing lighting levels, or any of the other factors that they experimented upon. The Hawthorne Effect has become one of the hardest inbuilt biases to eliminate or factor into the design of any experiment in psychology and beyond.
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8. Kitty Genovese Case
reports state that the attacker briefly left the scene and later returned to “finish off” his victim. It was later uncovered that many of these facts were exaggerated (there were more likely only a dozen witnesses and records show that some calls to police were made).
What this case later become famous for is the “Bystander Effect,” which states that the more bystanders that are present in a social situation, the less likely it is that anyone will step in and help. This effect has led to changes in medicine, psychology and many other areas. One famous example is the way CPR is taught to new learners. All students in CPR courses learn that they must assign one bystander the job of alerting authorities which minimizes the chances of no one calling for assistance.
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9. Learned Helplessness Experiment
Study Conducted by: Martin Seligman
Study Conducted in 1967 at the University of Pennsylvania
Experiment Details: In 1965, Martin Seligman and his colleagues were conducting research on classical conditioning, the process by which an
animal or human associates one thing with another.
Seligman’s experiment involved the ringing of a bell and then the administration of a light shock to a dog. After a number of pairings, the dog reacted to the shock even before it happened: as soon as the dog heard the bell, he reacted as though he’d already been shocked. During the course of this study something unexpected happened. Each dog was placed in a large crate that was divided down the middle with a low fence and the dog could see and jump over the fence easily. The floor on one side of the fence was electrified, but not on the other side of the fence. Seligman placed each dog on the electrified side and administered a light shock. He expected the dog to jump to the non-shocking side of the fence. In an unexpected turn, the dogs simply laid down. The hypothesis was that as the dogs learned from the first part of the experiment that there was nothing they could do to avoid the shocks, they gave up in the second part of the experiment. To prove this hypothesis the experimenters brought in a new set of animals and found that dogs with no history in the experiment would jump over the fence.
This condition was described as learned helplessness, where a human or animal does not attempt to get out of a negative situation because the past has taught them that they are helpless.
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10. Little Albert Experiment
This study proved that classical conditioning works on humans. One of the most important implications this finding has is that adult fears are often connected to early childhood experiences.
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11. Magical Number Seven
Study Conducted by: George A. Miller
Study Conducted in 1956 at Princeton University
Experiment Details: Frequently referred to as “ Miller’s Law,” the Magical Number Seven experiment purports that the number of objects an average human can hold in working memory is 7 ± 2. What this means is that the human memory capacity typically includes strings of words or concepts ranging from 5-9. This information on the limits to the capacity for processing information became one of the most highly cited papers in psychology.
The Magical Number Seven Experiment was published in 1956 by cognitive psychologist George A. Miller of Princeton University’s Department of
Psychology in Psychological Review. In the article, Miller discussed a concurrence between the limits of one-dimensional absolute judgment and the limits of short-term memory. In a one-dimensional absolute-judgment task, a person is presented with a number of stimuli that vary on one dimension (such as 10 different tones varying only in pitch) and responds to each stimulus with a corresponding response (learned before). Performance is almost perfect up to five or six different stimuli but declines as the number of different stimuli is increased. This means that a human’s maximum performance on one-dimensional absolute judgment can be described as an information store with the maximum capacity of approximately 2 to 3 bits of information, with the ability to distinguish between four and eight alternatives.
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12. Pavlov’s Dog Experiment
Study Conducted by: Ivan Pavlov
Study Conducted in the 1890s at the Military Medical Academy in
Study Conducted by: Muzafer and Carolyn Sherif
Study Conducted in 1954 at the University of Oklahoma
Experiment Details: This experiment, which studied group conflict, is considered by most to be outside the lines of what is considered ethically sound.
In 1954 researchers at the University of Oklahoma assigned 22 eleven- and twelve-year-old boys from similar backgrounds into two groups. The two groups were taken to separate areas of a summer camp facility where they were able to bond as social units. The groups were housed in separate cabins and neither group knew of the other’s existence for an entire week. The boys bonded with their cabin mates during that time. Once the two groups were allowed to have contact, they showed definite signs of prejudice and hostility toward each other even though they had only been given a very short time to develop their social group. To increase the conflict between the groups, the experimenters had them compete against each other in a series of activities. This created even more hostility and eventually the groups refused to eat in the same room. The final phase of the experiment involved turning the rival
groups into friends. The fun activities the experimenters had planned like shooting firecrackers and watching movies did not initially work, so they created teamwork exercises where the two groups were forced to collaborate. At the end of the experiment, the boys decided to ride the same bus home, demonstrating that conflict can be resolved and prejudice overcome through cooperation.
Many critics have compared this study to Golding’s Lord of the Flies novel as a classic example of prejudice and conflict resolution.
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14. Ross’ False Consensus Effect Study
Study Conducted by: Lee Ross
Study Conducted in 1977 at Stanford University
