10 famous psychology experiments

• The 25 Most Influential Psychological Experiments in History

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 human behavior during their psychological experiments 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, or better yet, a psychological experiment, 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 judged based on outward appearances. This exercise has since been repeated many times with similar outcomes.

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2. Asch Conformity Study

Study conducted by: dr. solomon asch.

Study Conducted in 1951 at Swarthmore College

Experiment Details: Dr. Solomon Asch conducted a groundbreaking study that was designed to evaluate a person’s likelihood to conform to a standard when there is pressure to do so.

A group of participants were shown pictures with lines of various lengths and were then asked a simple question: Which line is longest? The tricky part of this study was that in each group only one person was a true participant. The others were actors with a script. Most of the actors were instructed to give the wrong answer. Strangely, the one true participant almost always agreed with the majority, even though they knew they were giving the wrong answer.

The results of this study are important when we study social interactions among individuals in groups. This study is a famous example of the temptation many of us experience to conform to a standard during group situations and it showed that people often care more about being the same as others than they do about being right. It is still recognized as one of the most influential psychological experiments for understanding human behavior.

3. Bobo Doll Experiment

Study conducted by: dr. alburt bandura.

Study Conducted between 1961-1963 at Stanford University

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
• 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. 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. This is 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. This is 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. The Bobo Doll Experiment showed a groundbreaking way to study human behavior and it’s influences.

4. Car Crash Experiment

Study conducted by: elizabeth loftus and john palmer.

Study Conducted in 1974 at The University of California in Irvine

The participants watched slides of a car accident and were asked to describe what had happened as if they were eyewitnesses to the scene. The participants were put into two groups and each group was questioned using different wording such as “how fast was the car driving at the time of impact?” versus “how fast was the car going when it smashed into the other car?” The experimenters found that the use of different verbs affected the participants’ memories of the accident, showing that memory can be easily distorted.

This research suggests that memory can be easily manipulated by questioning technique. This means that information gathered after the event can merge with original memory causing incorrect recall or reconstructive memory. The addition of false details to a memory of an event is now referred to as confabulation. This concept has very important implications for the questions used in police interviews of eyewitnesses.

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:

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 cognitive 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.

6. Fantz’s Looking Chamber

Study conducted by: robert l. fantz.

Study Conducted in 1961 at the University of Illinois

Experiment Details: The study conducted by Robert L. Fantz is among the simplest, yet most important in the field of infant development and vision. In 1961, when this experiment was conducted, there very few ways to study what was going on in the mind of an infant. Fantz realized that the best way was to simply watch the actions and reactions of infants. He understood the fundamental factor that if there is something of interest near humans, they generally look at it.

To test this concept, Fantz set up a display board with two pictures attached. On one was a bulls-eye. 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.

7. Hawthorne Effect

Study conducted by: henry a. landsberger.

Study Conducted in 1955 at Hawthorne Works in Chicago, Illinois

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 in a building changed the productivity of the workers. What Mayo found was that the level of light made no difference in productivity. 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. They 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.

8. Kitty Genovese Case

Study conducted by: new york police force.

Study Conducted in 1964 in New York City

Experiment Details: The murder case of Kitty Genovese was never intended to be a psychological experiment, however it ended up having serious implications for the field.

According to a New York Times article, almost 40 neighbors witnessed Kitty Genovese being savagely attacked and murdered in Queens, New York in 1964. Not one neighbor called the police for help. Some 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.

9. Learned Helplessness Experiment

Study conducted by: martin seligman.

Study Conducted in 1967 at the University of Pennsylvania

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. 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. A human or animal does not attempt to get out of a negative situation because the past has taught them that they are helpless.

10. Little Albert Experiment

Study conducted by: john b. watson and rosalie rayner.

Study Conducted in 1920 at Johns Hopkins University

The experiment began by placing a white rat in front of the infant, who initially had no fear of the animal. Watson then produced a loud sound by striking a steel bar with a hammer every time little Albert was presented with the rat. After several pairings (the noise and the presentation of the white rat), the boy began to cry and exhibit signs of fear every time the rat appeared in the room. Watson also created similar conditioned reflexes with other common animals and objects (rabbits, Santa beard, etc.) until Albert feared them all.

This study proved that classical conditioning works on humans. One of its most important implications is that adult fears are often connected to early childhood experiences.

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. This means 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). The person 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 There is the ability to distinguish between four and eight alternatives.

12. Pavlov’s Dog Experiment

Study conducted by: ivan pavlov.

Study Conducted in the 1890s at the Military Medical Academy in St. Petersburg, Russia

Pavlov began with the simple idea that there are some things that a dog does not need to learn. He observed that dogs do not learn to salivate when they see food. This reflex is “hard wired” into the dog. This is an unconditioned response (a stimulus-response connection that required no learning).

Pavlov outlined that there are unconditioned responses in the animal by presenting a dog with a bowl of food and then measuring its salivary secretions. In the experiment, Pavlov used a bell as his neutral stimulus. Whenever he gave food to his dogs, he also rang a bell. After a number of repeats of this procedure, he tried the bell on its own. What he found was that the bell on its own now caused an increase in salivation. The dog had learned to associate the bell and the food. This learning created a new behavior. The dog salivated when he heard the bell. Because this response was learned (or conditioned), it is called a conditioned response. The neutral stimulus has become a conditioned stimulus.

This theory came to be known as classical conditioning.

13. Robbers Cave Experiment

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.

14. Ross’ False Consensus Effect Study

Study conducted by: lee ross.

Study Conducted in 1977 at Stanford University

Experiment Details: In 1977, a social psychology professor at Stanford University named Lee Ross conducted an experiment that, in lay terms, focuses on how people can incorrectly conclude that others think the same way they do, or form a “false consensus” about the beliefs and preferences of others. Ross conducted the study in order to outline how the “false consensus effect” functions in humans.

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In the first part of the study, participants were asked to read about situations in which a conflict occurred and then were told two alternative ways of responding to the situation. They were asked to do three things:

• Guess which option other people would choose
• Say which option they themselves would choose
• Describe the attributes of the person who would likely choose each of the two options

What the study showed was that most of the subjects believed that other people would do the same as them, regardless of which of the two responses they actually chose themselves. This phenomenon is referred to as the false consensus effect, where an individual thinks that other people think the same way they do when they may not. The second observation coming from this important study is that when participants were asked to describe the attributes of the people who will likely make the choice opposite of their own, they made bold and sometimes negative predictions about the personalities of those who did not share their choice.

15. The Schachter and Singer Experiment on Emotion

Study conducted by: stanley schachter and jerome e. singer.

Study Conducted in 1962 at Columbia University

Experiment Details: In 1962 Schachter and Singer conducted a ground breaking experiment to prove their theory of emotion.

In the study, a group of 184 male participants were injected with epinephrine, a hormone that induces arousal including increased heartbeat, trembling, and rapid breathing. The research participants were told that they were being injected with a new medication to test their eyesight. The first group of participants was informed the possible side effects that the injection might cause while the second group of participants were not. The participants were then placed in a room with someone they thought was another participant, but was actually a confederate in the experiment. The confederate acted in one of two ways: euphoric or angry. Participants who had not been informed about the effects of the injection were more likely to feel either happier or angrier than those who had been informed.

What Schachter and Singer were trying to understand was the ways in which cognition or thoughts influence human emotion. Their study illustrates the importance of how people interpret their physiological states, which form an important component of your emotions. Though their cognitive theory of emotional arousal dominated the field for two decades, it has been criticized for two main reasons: the size of the effect seen in the experiment was not that significant and other researchers had difficulties repeating the experiment.

16. Selective Attention / Invisible Gorilla Experiment

Study conducted by: daniel simons and christopher chabris.

Study Conducted in 1999 at Harvard University

Experiment Details: In 1999 Simons and Chabris conducted their famous awareness test at Harvard University.

Participants in the study were asked to watch a video and count how many passes occurred between basketball players on the white team. The video moves at a moderate pace and keeping track of the passes is a relatively easy task. What most people fail to notice amidst their counting is that in the middle of the test, a man in a gorilla suit walked onto the court and stood in the center before walking off-screen.

The study found that the majority of the subjects did not notice the gorilla at all, proving that humans often overestimate their ability to effectively multi-task. What the study set out to prove is that when people are asked to attend to one task, they focus so strongly on that element that they may miss other important details.

17. Stanford Prison Study

Study conducted by philip zimbardo.

Study Conducted in 1971 at Stanford University

The Stanford Prison Experiment was designed to study behavior of “normal” individuals when assigned a role of prisoner or guard. College students were recruited to participate. They were assigned roles of “guard” or “inmate.”  Zimbardo played the role of the warden. The basement of the psychology building was the set of the prison. Great care was taken to make it look and feel as realistic as possible.

The prison guards were told to run a prison for two weeks. They were told not to physically harm any of the inmates during the study. After a few days, the prison guards became very abusive verbally towards the inmates. Many of the prisoners became submissive to those in authority roles. The Stanford Prison Experiment inevitably had to be cancelled because some of the participants displayed troubling signs of breaking down mentally.

Although the experiment was conducted very unethically, many psychologists believe that the findings showed how much human behavior is situational. People will conform to certain roles if the conditions are right. The Stanford Prison Experiment remains one of the most famous psychology experiments of all time.

18. Stanley Milgram Experiment

Study conducted by stanley milgram.

Study Conducted in 1961 at Stanford University

Experiment Details: This 1961 study was conducted by Yale University psychologist Stanley Milgram. It was designed to measure people’s willingness to obey authority figures when instructed to perform acts that conflicted with their morals. The study was based on the premise that humans will inherently take direction from authority figures from very early in life.

Participants were told they were participating in a study on memory. They were asked to watch another person (an actor) do a memory test. They were instructed to press a button that gave an electric shock each time the person got a wrong answer. (The actor did not actually receive the shocks, but pretended they did).

Participants were told to play the role of “teacher” and administer electric shocks to “the learner,” every time they answered a question incorrectly. The experimenters asked the participants to keep increasing the shocks. Most of them obeyed even though the individual completing the memory test appeared to be in great pain. Despite these protests, many participants continued the experiment when the authority figure urged them to. They increased the voltage after each wrong answer until some eventually administered what would be lethal electric shocks.

This experiment showed that humans are conditioned to obey authority and will usually do so even if it goes against their natural morals or common sense.

19. Surrogate Mother Experiment

Study conducted by: harry harlow.

Study Conducted from 1957-1963 at the University of Wisconsin

Experiment Details: In a series of controversial experiments during the late 1950s and early 1960s, Harry Harlow studied the importance of a mother’s love for healthy childhood development.

In order to do this he separated infant rhesus monkeys from their mothers a few hours after birth and left them to be raised by two “surrogate mothers.” One of the surrogates was made of wire with an attached bottle for food. The other was made of soft terrycloth but lacked food. The researcher found that the baby monkeys spent much more time with the cloth mother than the wire mother, thereby proving that affection plays a greater role than sustenance when it comes to childhood development. They also found that the monkeys that spent more time cuddling the soft mother grew up to healthier.

This experiment showed that love, as demonstrated by physical body contact, is a more important aspect of the parent-child bond than the provision of basic needs. These findings also had implications in the attachment between fathers and their infants when the mother is the source of nourishment.

20. The Good Samaritan Experiment

Study conducted by: john darley and daniel batson.

Study Conducted in 1973 at The Princeton Theological Seminary (Researchers were from Princeton University)

Experiment Details: In 1973, an experiment was created by John Darley and Daniel Batson, to investigate the potential causes that underlie altruistic behavior. The researchers set out three hypotheses they wanted to test:

• People thinking about religion and higher principles would be no more inclined to show helping behavior than laymen.
• People in a rush would be much less likely to show helping behavior.
• People who are religious for personal gain would be less likely to help than people who are religious because they want to gain some spiritual and personal insights into the meaning of life.

Student participants were given some religious teaching and instruction. They were then were told to travel from one building to the next. Between the two buildings was a man lying injured and appearing to be in dire need of assistance. The first variable being tested was the degree of urgency impressed upon the subjects, with some being told not to rush and others being informed that speed was of the essence.

The results of the experiment were intriguing, with the haste of the subject proving to be the overriding factor. When the subject was in no hurry, nearly two-thirds of people stopped to lend assistance. When the subject was in a rush, this dropped to one in ten.

People who were on the way to deliver a speech about helping others were nearly twice as likely to help as those delivering other sermons,. This showed that the thoughts of the individual were a factor in determining helping behavior. Religious beliefs did not appear to make much difference on the results. Being religious for personal gain, or as part of a spiritual quest, did not appear to make much of an impact on the amount of helping behavior shown.

21. The Halo Effect Experiment

Study conducted by: richard e. nisbett and timothy decamp wilson.

Study Conducted in 1977 at the University of Michigan

Experiment Details: The Halo Effect states that people generally assume that people who are physically attractive are more likely to:

• be intelligent
• be friendly
• display good judgment

To prove their theory, Nisbett and DeCamp Wilson created a study to prove that people have little awareness of the nature of the Halo Effect. They’re not aware that it influences:

• their personal judgments
• the production of a more complex social behavior

In the experiment, college students were the research participants. They were asked to evaluate a psychology instructor as they view him in a videotaped interview. The students were randomly assigned to one of two groups. Each group was shown one of two different interviews with the same instructor. The instructor is a native French-speaking Belgian who spoke English with a noticeable accent. In the first video, the instructor presented himself as someone:

• respectful of his students’ intelligence and motives
• flexible in his approach to teaching
• enthusiastic about his subject matter

In the second interview, he presented himself as much more unlikable. He was cold and distrustful toward the students and was quite rigid in his teaching style.

After watching the videos, the subjects were asked to rate the lecturer on:

• physical appearance

His mannerisms and accent were kept the same in both versions of videos. The subjects were asked to rate the professor on an 8-point scale ranging from “like extremely” to “dislike extremely.” Subjects were also told that the researchers were interested in knowing “how much their liking for the teacher influenced the ratings they just made.” Other subjects were asked to identify how much the characteristics they just rated influenced their liking of the teacher.

After responding to the questionnaire, the respondents were puzzled about their reactions to the videotapes and to the questionnaire items. The students had no idea why they gave one lecturer higher ratings. Most said that how much they liked the lecturer had not affected their evaluation of his individual characteristics at all.

The interesting thing about this study is that people can understand the phenomenon, but they are unaware when it is occurring. Without realizing it, humans make judgments. Even when it is pointed out, they may still deny that it is a product of the halo effect phenomenon.

22. The Marshmallow Test

Study conducted by: walter mischel.

Study Conducted in 1972 at Stanford University

In his 1972 Marshmallow Experiment, children ages four to six were taken into a room where a marshmallow was placed in front of them on a table. Before leaving each of the children alone in the room, the experimenter informed them that they would receive a second marshmallow if the first one was still on the table after they returned in 15 minutes. The examiner recorded how long each child resisted eating the marshmallow and noted whether it correlated with the child’s success in adulthood. A small number of the 600 children ate the marshmallow immediately and one-third delayed gratification long enough to receive the second marshmallow.

In follow-up studies, Mischel found that those who deferred gratification were significantly more competent and received higher SAT scores than their peers. This characteristic likely remains with a person for life. While this study seems simplistic, the findings outline some of the foundational differences in individual traits that can predict success.

23. The Monster Study

Study conducted by: wendell johnson.

Study Conducted in 1939 at the University of Iowa

Experiment Details: The Monster Study received this negative title due to the unethical methods that were used to determine the effects of positive and negative speech therapy on children.

Wendell Johnson of the University of Iowa selected 22 orphaned children, some with stutters and some without. The children were in two groups. The group of children with stutters was placed in positive speech therapy, where they were praised for their fluency. The non-stutterers were placed in negative speech therapy, where they were disparaged for every mistake in grammar that they made.

As a result of the experiment, some of the children who received negative speech therapy suffered psychological effects and retained speech problems for the rest of their lives. They were examples of the significance of positive reinforcement in education.

The initial goal of the study was to investigate positive and negative speech therapy. However, the implication spanned much further into methods of teaching for young children.

24. Violinist at the Metro Experiment

Study conducted by: staff at the washington post.

Study Conducted in 2007 at a Washington D.C. Metro Train Station

During the study, pedestrians rushed by without realizing that the musician playing at the entrance to the metro stop was Grammy-winning musician, Joshua Bell. Two days before playing in the subway, he sold out at a theater in Boston where the seats average $100. He played one of the most intricate pieces ever written with a violin worth 3.5 million dollars. In the 45 minutes the musician played his violin, only 6 people stopped and stayed for a while. Around 20 gave him money, but continued to walk their normal pace. He collected $32.

The study and the subsequent article organized by the Washington Post was part of a social experiment looking at:

• the priorities of people

Gene Weingarten wrote about the social experiment: “In a banal setting at an inconvenient time, would beauty transcend?” Later he won a Pulitzer Prize for his story. Some of the questions the article addresses are:

• Do we perceive beauty?
• Do we stop to appreciate it?
• Do we recognize the talent in an unexpected context?

As it turns out, many of us are not nearly as perceptive to our environment as we might like to think.

25. Visual Cliff Experiment

Study conducted by: eleanor gibson and richard walk.

Study Conducted in 1959 at Cornell University

Experiment Details: In 1959, psychologists Eleanor Gibson and Richard Walk set out to study depth perception in infants. They wanted to know if depth perception is a learned behavior or if it is something that we are born with. To study this, Gibson and Walk conducted the visual cliff experiment.

They studied 36 infants between the ages of six and 14 months, all of whom could crawl. The infants were placed one at a time on a visual cliff. A visual cliff was created using a large glass table that was raised about a foot off the floor. Half of the glass table had a checker pattern underneath in order to create the appearance of a ‘shallow side.’

In order to create a ‘deep side,’ a checker pattern was created on the floor; this side is the visual cliff. The placement of the checker pattern on the floor creates the illusion of a sudden drop-off. Researchers placed a foot-wide centerboard between the shallow side and the deep side. Gibson and Walk found the following:

• Nine of the infants did not move off the centerboard.
• All of the 27 infants who did move crossed into the shallow side when their mothers called them from the shallow side.
• Three of the infants crawled off the visual cliff toward their mother when called from the deep side.
• When called from the deep side, the remaining 24 children either crawled to the shallow side or cried because they could not cross the visual cliff and make it to their mother.

What this study helped demonstrate is that depth perception is likely an inborn train in humans.

Among these experiments and psychological tests, we see boundaries pushed and theories taking on a life of their own. It is through the endless stream of psychological experimentation that we can see simple hypotheses become guiding theories for those in this field. The greater field of psychology became a formal field of experimental study in 1879, when Wilhelm Wundt established the first laboratory dedicated solely to psychological research in Leipzig, Germany. Wundt was the first person to refer to himself as a psychologist. Since 1879, psychology has grown into a massive collection of:

• methods of practice

It’s also a specialty area in the field of healthcare. None of this would have been possible without these and many other important psychological experiments that have stood the test of time.

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About the Author

After earning a Bachelor of Arts in Psychology from Rutgers University and then a Master of Science in Clinical and Forensic Psychology from Drexel University, Kristen began a career as a therapist at two prisons in Philadelphia. At the same time she volunteered as a rape crisis counselor, also in Philadelphia. After a few years in the field she accepted a teaching position at a local college where she currently teaches online psychology courses. Kristen began writing in college and still enjoys her work as a writer, editor, professor and mother.

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20 Famous Psychology Experiments That Shaped Our Understanding

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1.stanford prison experiment.

2.Milgram Experiment

3.little albert experiment.

4.Asch Conformity Experiment

5.harlow’s monkey experiment.

6.Bobo Doll Experiment

7.the marshmallow test.

8.Robbers Cave Experiment

9.the monster study.

10.The Standford Marshmallow Experiment

11.the hawthorne effect.

12.The Strange Situation

13.the still face experiment.

14.Pavlov’s Dogs

15.the milgram experiment.

16.The Robbers Cave Experiment

17.the harlow monkey experiment, 18.the bystander effect, 19.the zimbardo prison experiment.

20.The Ainsworth Strange Situation Experiment

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Social Psychology Experiments: 10 Of The Most Famous Studies

Ten of the most influential social psychology experiments explain why we sometimes do dumb or irrational things. 

Ten of the most influential social psychology experiments explain why we sometimes do dumb or irrational things.

“I have been primarily interested in how and why ordinary people do unusual things, things that seem alien to their natures. Why do good people sometimes act evil? Why do smart people sometimes do dumb or irrational things?” –Philip Zimbardo

Like famous social psychologist Professor Philip Zimbardo (author of The Lucifer Effect: Understanding How Good People Turn Evil ), I’m also obsessed with why we do dumb or irrational things.

The answer quite often is because of other people — something social psychologists have comprehensively shown.

Each of the 10 brilliant social psychology experiments below tells a unique, insightful story relevant to all our lives, every day.

Click the link in each social psychology experiment to get the full description and explanation of each phenomenon.

1. Social Psychology Experiments: The Halo Effect

The halo effect is a finding from a famous social psychology experiment.

It is the idea that global evaluations about a person (e.g. she is likeable) bleed over into judgements about their specific traits (e.g. she is intelligent).

It is sometimes called the “what is beautiful is good” principle, or the “physical attractiveness stereotype”.

It is called the halo effect because a halo was often used in religious art to show that a person is good.

2. Cognitive Dissonance

Cognitive dissonance is the mental discomfort people feel when trying to hold two conflicting beliefs in their mind.

People resolve this discomfort by changing their thoughts to align with one of conflicting beliefs and rejecting the other.

The study provides a central insight into the stories we tell ourselves about why we think and behave the way we do.

3. Robbers Cave Experiment: How Group Conflicts Develop

The Robbers Cave experiment was a famous social psychology experiment on how prejudice and conflict emerged between two group of boys.

It shows how groups naturally develop their own cultures, status structures and boundaries — and then come into conflict with each other.

For example, each country has its own culture, its government, legal system and it draws boundaries to differentiate itself from neighbouring countries.

One of the reasons the became so famous is that it appeared to show how groups could be reconciled, how peace could flourish.

The key was the focus on superordinate goals, those stretching beyond the boundaries of the group itself.

4. Social Psychology Experiments: The Stanford Prison Experiment

The Stanford prison experiment was run to find out how people would react to being made a prisoner or prison guard.

The psychologist Philip Zimbardo, who led the Stanford prison experiment, thought ordinary, healthy people would come to behave cruelly, like prison guards, if they were put in that situation, even if it was against their personality.

It has since become a classic social psychology experiment, studied by generations of students and recently coming under a lot of criticism.

5. The Milgram Social Psychology Experiment

The Milgram experiment , led by the well-known psychologist Stanley Milgram in the 1960s, aimed to test people’s obedience to authority.

The results of Milgram’s social psychology experiment, sometimes known as the Milgram obedience study, continue to be both thought-provoking and controversial.

The Milgram experiment discovered people are much more obedient than you might imagine.

Fully 63 percent of the participants continued administering what appeared like electric shocks to another person while they screamed in agony, begged to stop and eventually fell silent — just because they were told to.

6. The False Consensus Effect

The false consensus effect is a famous social psychological finding that people tend to assume that others agree with them.

It could apply to opinions, values, beliefs or behaviours, but people assume others think and act in the same way as they do.

It is hard for many people to believe the false consensus effect exists because they quite naturally believe they are good ‘intuitive psychologists’, thinking it is relatively easy to predict other people’s attitudes and behaviours.

In reality, people show a number of predictable biases, such as the false consensus effect, when estimating other people’s behaviour and its causes.

7. Social Psychology Experiments: Social Identity Theory

Social identity theory helps to explain why people’s behaviour in groups is fascinating and sometimes disturbing.

People gain part of their self from the groups they belong to and that is at the heart of social identity theory.

The famous theory explains why as soon as humans are bunched together in groups we start to do odd things: copy other members of our group, favour members of own group over others, look for a leader to worship and fight other groups.

8. Negotiation: 2 Psychological Strategies That Matter Most

Negotiation is one of those activities we often engage in without quite realising it.

Negotiation doesn’t just happen in the boardroom, or when we ask our boss for a raise or down at the market, it happens every time we want to reach an agreement with someone.

In a classic, award-winning series of social psychology experiments, Morgan Deutsch and Robert Krauss investigated two central factors in negotiation: how we communicate with each other and how we use threats.

9. Bystander Effect And The Diffusion Of Responsibility

The bystander effect in social psychology is the surprising finding that the mere presence of other people inhibits our own helping behaviours in an emergency.

The bystander effect social psychology experiments are mentioned in every psychology textbook and often dubbed ‘seminal’.

This famous social psychology experiment on the bystander effect was inspired by the highly publicised murder of Kitty Genovese in 1964.

It found that in some circumstances, the presence of others inhibits people’s helping behaviours — partly because of a phenomenon called diffusion of responsibility.

10. Asch Conformity Experiment: The Power Of Social Pressure

The Asch conformity experiments — some of the most famous every done — were a series of social psychology experiments carried out by noted psychologist Solomon Asch.

The Asch conformity experiment reveals how strongly a person’s opinions are affected by people around them.

In fact, the Asch conformity experiment shows that many of us will deny our own senses just to conform with others.

Author: Dr Jeremy Dean

Psychologist, Jeremy Dean, PhD is the founder and author of PsyBlog. He holds a doctorate in psychology from University College London and two other advanced degrees in psychology. He has been writing about scientific research on PsyBlog since 2004. View all posts by Dr Jeremy Dean

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The 11 Most Influential Psychological Experiments in History

The history of psychology is marked by groundbreaking experiments that transformed our understanding of the human mind. These 11 Most Influential Psychological Experiments in History stand out as pivotal, offering profound insights into behaviour, cognition, and the complexities of human nature.

In this PsychologyOrg article, we’ll explain these key experiments, exploring their impact on our understanding of human behaviour and the intricate workings of the mind.

Table of Contents

Experimental psychology.

Experimental psychology is a branch of psychology that uses scientific methods to study human behaviour and mental processes. Researchers in this field design experiments to test hypotheses about topics such as perception, learning, memory, emotion, and motivation.

They use a variety of techniques to measure and analyze behaviour and mental processes, including behavioural observations, self-report measures, physiological recordings, and computer simulations. The findings of experimental psychology studies can have important implications for a wide range of fields, including education, healthcare, and public policy.

Experimental Psychology, Psychologists have long tried to gain insight into how we perceive the world, to understand what motivates our behavior. They have made great strides in lifting that veil of mystery. In addition to providing us with food for stimulating party conversations, some of the most famous psychological experiments of the last century reveal surprising and universal truths about nature.

Throughout the history of psychology, revolutionary experiments have reshaped our comprehension of the human mind. These 11 experiments are pivotal, providing deep insights into human behaviour, cognition, and the intricate facets of human nature.

1. Kohler and the Chimpanzee experiment

Wolfgang Kohler studied the insight process by observing the behaviour of chimpanzees in a problem situation. In the experimental situation, the animals were placed in a cage outside of which food, for example, a banana, was stored. There were other objects in the cage, such as sticks or boxes. The animals participating in the experiment were hungry, so they needed to get to the food. At first, the chimpanzee used sticks mainly for playful activities; but suddenly, in the mind of the hungry chimpanzee, a relationship between sticks and food developed.

The cane, from an object to play with, became an instrument through which it was possible to reach the banana placed outside the cage. There has been a restructuring of the perceptual field: Kohler stressed that the appearance of the new behaviour was not the result of random attempts according to a process of trial and error. It is one of the first experiments on the intelligence of chimpanzees.

2. Harlow’s experiment on attachment with monkeys

In a scientific paper (1959), Harry F. Harlow described how he had separated baby rhesus monkeys from their mothers at birth, and raised them with the help of “puppet mothers”: in a series of experiments he compared the behavior of monkeys in two situations:

Little monkeys with a puppet mother without a bottle, but covered in a soft, fluffy, and furry fabric. Little monkeys with a “puppet” mother that supplied food, but was covered in wire. The little monkeys showed a clear preference for the “furry” mother, spending an average of fifteen hours a day attached to her, even though they were exclusively fed by the “suckling” puppet mother. conclusions of the Harlow experiment: all the experiments showed that the pleasure of contact elicited attachment behaviours, but the food did not.

3. The Strange Situation by Mary Ainsworth

Building on Bowlby’s attachment theory, Mary Ainsworth and colleagues (1978) have developed an experimental method called the Strange Situation, to assess individual differences in attachment security. The Strange Situation includes a series of short laboratory episodes in a comfortable environment and the child’s behaviors are observed.

Ainsworth and colleagues have paid special attention to the child’s behaviour at the time of reunion with the caregiver after a brief separation, thus identifying three different attachment patterns or styles, so called from that moment on. kinds of attachment according to Mary Ainsworth:

Secure attachment (63% of the dyads examined) Anxious-resistant or ambivalent (16%) Avoidant (21%) The Strange Situation by Mary Ainsworth

In a famous 1971 experiment, known as the Stanford Prison, Zimbardo and a team of collaborators reproduced a prison in the garages of Stanford University to study the behaviour of subjects in a context of very particular and complex dynamics. Let’s see how it went and the thoughts on the Stanford prison experiment. The participants (24 students) were randomly divided into two groups:

“ Prisoners “. The latter were locked up in three cells in the basement of a University building for six days; they were required to wear a white robe with a paper over it and a chain on the right ankle. “ Guards “. The students who had the role of prison guards had to watch the basement, choose the most appropriate methods to maintain order, and make the “prisoners” perform various tasks; they were asked to wear dark glasses and uniforms, and never to be violent towards the participants of the opposite role. However, the situation deteriorated dramatically: the fake police officers very soon began to seriously mistreat and humiliate the “detainees”, so it was decided to discontinue the experiment.

4. Jane Elliot’s Blue Eyes Experiment

On April 5, 1968, in a small school in Riceville, Iowa, Professor Jane Elliot decided to give a practical lesson on racism to 28 children of about eight years of age through the blue eyes brown eyes experiment.

“Children with brown eyes are the best,” the instructor began. “They are more beautiful and intelligent.” She wrote the word “melanin” on the board and explained that it was a substance that made people intelligent. Dark-eyed children have more, so they are more intelligent, while blue-eyed children “go hand in hand.”

In a very short time, the brown-eyed children began to treat their blue-eyed classmates with superiority, who in turn lost their self-confidence. A very good girl started making mistakes during arithmetic class, and at recess, she was approached by three little friends with brown eyes “You have to apologize because you get in their way and because we are the best,” said one of them. The girl hastened to apologize. This is one of the psychosocial experiments demonstrating how beliefs and prejudices play a role.

5. The Bobo de Bbandura doll

Albert Bandura gained great fame for the Bobo doll experiment on child imitation aggression, where:

A group of children took as an example, by visual capacity, the adults in a room, without their behaviour being commented on, hit the Bobo doll. Other contemporaries, on the other hand, saw adults sitting, always in absolute silence, next to Bobo.

Finally, all these children were brought to a room full of toys, including a doll like Bobo. Of the 10 children who hit the doll, 8 were those who had seen it done before by an adult. This explains how if a model that we follow performs a certain action, we are tempted to imitate it and this happens especially in children who still do not have the experience to understand for themselves if that behaviour is correct or not.

6. Milgram’s experiment

The Milgram experiment was first carried out in 1961 by psychologist Stanley Milgram, as an investigation into the degree of our deference to authority. A subject is invited to give an electric shock to an individual playing the role of the student, positioned behind a screen when he does not answer a question correctly. An authorized person then tells the subject to gradually increase the intensity of the shock until the student screams in pain and begs to stop.

No justification is given, except for the fact that the authorized person tells the subject to obey. In reality, it was staged: there was absolutely no electric shock given, but in the experiment two-thirds of the subjects were influenced by what they thought was a 450-volt shock, simply because a person in authority told them they would not be responsible for it. nothing.

7. little Albert

We see little Albert’s experiment on unconditioned stimulus, which must be the most famous psychological study. John Watson and Rosalie Raynor showed a white laboratory rat to a nine-month-old boy, little Albert. At first, the boy showed no fear, but then Watson jumped up from behind and made him flinch with a sudden noise by hitting a metal bar with a hammer. Of course, the noise frightened little Albert, who began to cry.

Every time the rat was brought out, Watson and Raynor would rattle the bar with their hammer to scare the poor boy away. Soon the mere sight of the rat was enough to reduce little Albert to a trembling bundle of nerves: he had learned to fear the sight of a rat, and soon afterwards began to fear a series of similar objects shown to him.

8. Pavlov’s dog

Ivan Pavlov’s sheepdog became famous for his experiments that led him to discover what we call “classical conditioning” or “Pavlovian reflex” and is still a very famous psychological experiment today. Hardly any other psychological experiment is cited so often and with such gusto as Pavlov’s theory expounded in 1905: the Russian physiologist had been impressed by the fact that his dogs did not begin to drool at the sight of food, but rather when they heard it. to the laboratory employees who took it away.

He researched it and ordered a buzzer to ring every time it was mealtime. Very soon the sound of the doorbell was enough for the dogs to start drooling: they had connected the signal to the arrival of food.

9. Asch’s experiment

It is about a social psychology experiment carried out in 1951 by the Polish psychologist Solomon Asch on the influence of the majority and social conformity.

The experiment is based on the idea that being part of a group is a sufficient condition to change a person’s actions, judgments, and visual perceptions. The very simple experiment consisted of asking the subjects involved to associate line 1 drawn on a white sheet with the corresponding one, choosing between three different lines A, B, and C present on another sheet. Only one was identical to the other, while the other two were longer or shorter.

The experimentation was carried out in three phases. As soon as one of the subjects, Asch’s accomplice gave a wrong answer associating line 1 with the wrong one, the other members of the group also made the same mistake, even though the correct answer was more than obvious. The participants questioned the reason for this choice and responded that aware of the correct answer, they had decided to conform to the group, adapting to those who had preceded them.

psychotherapy definition types and techniques | Psychotherapy vs therapy Psychologyorg.com

10. Rosenbaum’s experiment

Among the most interesting investigations in this field, an experiment carried out by David Rosenhan (1923) to document the low validity of psychiatric diagnoses stands out. Rosenhan admitted eight assistants to various psychiatric hospitals claiming psychotic symptoms, but once they entered the hospital they behaved as usual.

Despite this, they were held on average for 19 days, with all but one being diagnosed as “psychotic”. One of the reasons why the staff is not aware of the “normality” of the subjects, is, according to Rosenhan, the very little contact between the staff and the patients.

11. Bystander Effect (1968)

The Bystander Effect studied in 1968 after the tragic case of Kitty Genovese, explores how individuals are less likely to intervene in emergencies when others are present. The original research by John Darley and Bibb Latané involved staged scenarios where participants believed they were part of a discussion via intercom.

In the experiment, participants were led to believe they were communicating with others about personal problems. Unknown to them, the discussions were staged, and at a certain point, a participant (confederate) pretended to have a seizure or needed help.

The results were startling. When participants believed they were the sole witness to the emergency, they responded quickly and sought help. However, when they thought others were also present (but were confederates instructed to not intervene), the likelihood of any individual offering help significantly decreased. This phenomenon became known as the Bystander Effect.

The diffusion of responsibility, where individuals assume others will take action, contributes to this effect. The presence of others creates a diffusion of responsibility among bystanders, leading to a decreased likelihood of any single individual taking action.

This experiment highlighted the social and psychological factors influencing intervention during emergencies and emphasized the importance of understanding bystander behaviour in critical situations.

The journey through the “11 Most Influential Psychological Experiments in History” illuminates the profound impact these studies have had on our understanding of human behaviour, cognition, and social dynamics.

Each experiment stands as a testament to the dedication of pioneering psychologists who dared to delve into the complexities of the human mind. From Milgram’s obedience studies to Zimbardo’s Stanford Prison Experiment, these trials have shaped not only the field of psychology but also our societal perceptions and ethical considerations in research.

They serve as timeless benchmarks, reminding us of the ethical responsibilities and the far-reaching implications of delving into the human psyche. The enduring legacy of these experiments lies not only in their scientific contributions but also in the ethical reflections they provoke, urging us to navigate the boundaries of knowledge with caution, empathy, and an unwavering commitment to understanding the intricacies of our humanity.

What is the most famous experiment in the history of psychology?

One of the most famous experiments is the Milgram Experiment, conducted by Stanley Milgram in the 1960s. It investigated obedience to authority figures and remains influential in understanding human behaviour.

Who wrote the 25 most influential psychological experiments in history?

The book “The 25 Most Influential Psychological Experiments in History” was written by Michael Shermer, a science writer and historian of science.

What is the history of experimental psychology?

Experimental psychology traces back to Wilhelm Wundt, often considered the father of experimental psychology. He established the first psychology laboratory in 1879 at the University of Leipzig, marking the formal beginning of experimental psychology as a distinct field.

What was the psychological experiment in the 1960s?

Many significant psychological experiments were conducted in the 1960s. One notable example is the Stanford Prison Experiment led by Philip Zimbardo, which examined the effects of situational roles on behaviour.

Who was the first experimental psychologist?

Wilhelm Wundt is often regarded as the first experimental psychologist due to his establishment of the first psychology laboratory and his emphasis on empirical research methods in psychology.

If you want to read more articles similar to  The 11 Most Influential Psychological Experiments in History , we recommend that you enter our  Psychology  category.

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10 great psychology experiments

by Chris Woodford . Last updated: December 31, 2021.

S tare in the mirror and you'll find a strong sense of self staring back. Every one of us thinks we have a good idea who we are and what we're about—how we laugh and live and love, and all the complicated rest. But if you're a student of psychology —the fascinating science of human behaviour—you may well stare at your reflection with a wary eye. Because you'll know already that the ideas you have about yourself and other people can be very wide of the mark.

You might think you can learn a lot about human behaviour simply by observing yourself, but psychologists know that isn't really true. "Introspection" (thinking about yourself) has long been considered a suspect source of psychological research, even though one of the founding fathers of the science, William James, gained many important insights with its help. [1] Fortunately, there are thousands of rigorous experiments you can study that will do the job much more objectively and scientifically. And here's a quick selection of 10 of my favourites.

Listen instead... or scroll to keep reading

1: are you really paying attention (simons & chabris, 1999).

“ ...our findings suggest that unexpected events are often overlooked... ” Simons & Chabris, 1999

You can read a book or you can listen to the radio, but can you do both at once? Maybe you can listen to a soft-rock album you've heard hundreds of times before and simultaneously plod your way through an undemanding crime novel, but how about listening to a complex political debate while trying to revise for a politics exam? What about listening to a German radio station while reading a French novel? What about mixing things up a bit more. You can iron your clothes while listening to the radio, no problem. But how about trying to follow (and visualize) the radio commentary on a football game while driving a highway you've never been along before? That's much more challenging because both things call on your brain's ability to process spatial information and one tends to interfere with the other. (There are very good reasons why it's unwise to use a cellphone while you're driving—and in some countries it's illegal.)

Generally speaking, we can do—and pay attention—to only so many things at once. That's no big surprise. However human attention works (and there are many theories about that), it's obviously not unlimited. What is surprising is how we pay attention to some things, in some situations, but not others. Psychologists have long studied something they call the cocktail-party effect . If you're at a noisy party, you can selectively switch your attention to any of the voices around you, just like tuning in a radio, while ignoring all the rest. Even more striking, if you're listening to one person and someone else happens to say your name, your ears will prick up and your attention will instantly switch to the other person instead. So your brain must be aware of much more than you think, even if it's not giving everything its full attention, all the time. [2]

Photo: Would you spot a gorilla if it were in plain sight? Picture by Richard Ruggiero courtesy of US Fish and Wildlife Service National Digital Library .

Sometimes, when we're really paying attention, we aren't easily distracted, even by drastic changes we ought to notice. A particularly striking demonstration of this comes from the work of Daniel Simons and Christopher Chabris (1999), who built on earlier work by the esteemed cognitive psychologist Ulric Neisser and colleagues. [3] Simons and Chabris made a video of people in black or white shirts throwing a basketball back and forth and asked viewers to count the number of passes made by the white-shirted players. You can watch it here .

Half the viewers failed to notice something else that happens at the same time (the gorilla-suited person wandering across the set)—an extraordinary example of something psychologists call inattentional blindness (in plain English: failure to see something you really should have spotted). A related phenomenon called change blindness explains why we generally fail to notice things like glaring continuity errors in movies: we don't expect to see them—and so we don't. Whether experiments like "the invisible gorilla" allow us to conclude broader things about human nature is a moot point, but it's certainly fair to say (as Simons and Chabris argue) that they reveal "critically important limitations of our cognitive abilities." None of us are as smart as we like to think, but just because we fail and fall short that doesn't make us bad people; we'd do a lot better if we understood and recognized our shortcomings. [4]

2: Are you trying too hard? (Aronson, 1966)

No-one likes a smart-aleck, so the saying goes, but just how true is that? Even if you really hate someone who has everything—the good looks, the great house, the well-paid job—it tuns out that there are certain circumstances in which you'll like them a whole lot more: if they suddenly make a stupid mistake. This not-entirely-surprising bit of psychology mirrors everyday experience: we like our fellow humans slightly flawed, down-to-earth, and somewhat relatable. Known as the pratfall effect , it was famously demonstrated back in 1966 by social psychologist Elliot Aronson. [5]

“ ...a superior person may be viewed as superhuman and, therefore, distant; a blunder tends to humanize him and, consequently, increases his attractiveness. ” Aronson et al, 1966

Aronson made taped audio recordings of two very different people talking about themselves and answering 50 difficult questions, which were supposedly part of an interview for a college quiz team. One person was very superior, got almost all the questions right, and revealed (in passing) that they were generally excellent at what they did (an honors student, yearbook editor, and member of the college track team). The other person was much more mediocre, got many questions wrong, and revealed (in passing) that they were much more of a plodder (average grades in high school, proofreader of the yearbook, and failed to make the track team). In the experiment, "subjects" (that's what psychologists call the people who take part in their trials) had to listen to the recordings of the two people and rate them on various things, including their likeability. But there was a twist. In some of the taped interviews, an extra bit (the "pratfall") was added at the end where either the superior person or the mediocrity suddenly shouted "Oh my goodness I've spilled coffee all over my new suit", accompanied by the sounds of a clattering chair and general chaos (noises that were identically spliced onto both tapes).

Artwork: Mistakes make you more likeable—if you're considered competent to begin with.

What Aronson found was that the superior person was rated more attractive with the pratfall at the end of their interview; the inferior person, less so. In other words, a pratfall can really work in your favor, but only if you're considered halfway competent to begin with; if not, it works against you. Knowingly or otherwise, smart celebrities and politicians often appear to take advantage of this to improve their popularity.

3: Is the past a foreign country? (Loftus and Palmer, 1974)

Attention isn't the only thing that lets us down; memory is hugely infallible too—and it's one of the strangest and most complex things psychologists study. Can you remember where you were when the Twin Towers fell in 2001 or (if you're much older and willing to go back further) when JFK was shot in Dallas in 1963? You might remember a girl you were in kindergarten with 20 years ago, but perhaps you can't remember the guy you met last week, last night, or even 10 minutes ago. What about the so-called tip-of-the-tongue phenomenon where you're certain you know a word or fact or name, and you can even describe what it's like ("It's a really short word, maybe beginning with 'F'..."), but you can't bring it instantly to mind? [6] How about the madeleine effect, where the taste or smell or something suddenly sets off an incredibly powerful involuntary memory ? What about déjà-vu : a jarring true-false memory—the strong sense something is very familiar when it can't possibly be? [7] How about the curious split between short- and long-term memories or between "procedural memory" (knowing how to do things or follow instructions) and "declarative memory" (knowing facts), which breaks down further into "semantic memory" (general knowledge about things) and "episodic memory" (specific things that have happened to you). What about the many flavors of selective memory failure, such as seniors who can remember the name of a high-school sweetheart but can't recall their own name? Or sudden episodes of amnesia? Human memory is a massive—and massively complex—subject. And any comprehensive theory of it needs to be able to explain a lot.

“ ...the questions asked subsequent to an event can cause a reconstruction in one's memory of that event.. ” Loftus & Palmer, 1974

Much of the time, poor memory is just a nuisance and we all have tricks for working around it—from slapping Post-It notes on the mirror to setting reminders on our phones. But there's one situation where poor memories can be a matter of life or death: in criminal investigation and court testimony. Suppose you give evidence in a trial based on events you think you remember that happened years ago—and suppose your evidence helps to convict a "murderer" who's subsequently sentenced to death. But what if your memory was quite wrong and the person was innocent?

One of the most famous studies of just how flawed our memories can be was made by psychologists Elizabeth Loftus and John Palmer in 1974. [8] After showing their subjects footage of a car accident, they tested their memories some time later by asking "About how fast were the cars going when they smashed into each other?" or using "collided," "bumped," "contacted," or "hit" in place of smashed. Those asked the first—leading—question reported higher speeds. Later, the subjects were asked if they'd seen any broken glass and those asked the leading question ("smashed") were much more likely to say "yes" even though there was no broken glass in the film. So our memories are much more fluid, far less fixed, than we suppose.

Artwork: The words we use to probe our memories can affect the memories we think we have.

This classic experiment very powerfully illustrates the potential unreliability of eyewitness testimony in criminal investigations, but the work of Elizabeth Loftus on so-called "false memory syndrome" has had far-reaching impacts in provocative areas, such as people's alleged recollections of alien abduction , multiple personality disorder , and memories of childhood abuse . Ultimately, what it demonstrates is that memory is fallible and remembering is sometimes less of a mechanical activity (pulling a dusty book from long-neglected library shelf) than a creative and recreative one (rewriting the book partly or completely to compensate for the fact that the print has faded with time). [9]

4. Do you cave in to peer pressure? (Milgram, 1963)

Experiments like the three we've considered so far might cast an uncomfortable shadow, yet most of us are still convinced we're rational, reasonable people, most of the time. Asked to predict how we'd behave in any given situation, we'd be able to give a pretty good account of ourselves—or so you might think. Consider the question of whether you'd ever, under any circumstances, torture another human being and you'd probably be appalled at the prospect. "Of course not!" And yet, as Yale University's Stanley Milgram famously demonstrated in the 1960s and 1970s, you'd probably be mistaken. [10]

Artwork: The Milgram experiment: a shocking turn of events.

Milgram's experiments on obedience to authority have been widely discussed and offered as explanations for all kinds of things, from minor everyday cruelty to the appalling catalogue of repugnant human behavior witnessed during the Nazi Holocaust. Today, they're generally considered unethical because they're deceptive and could, potentially, damage the mental health of people taking part in them (a claim Milgram himself investigated and refuted). [26]

“ ...the conflict stems from the opposition of two deeply ingrained behavior dispositions: first, the disposition not to harm other people, and second, the tendency to obey those whom we perceive to be legitimate authorities. ” Milgram, 1963

Though Milgram's studies have not been repeated, related experiments have sought to shed more light on why people find themselves participating in quite disturbing forms of behavior. One explanation is that, like willing actors, we simply assume the roles we're given and play our parts well. In 1972, Stanford University's Philip Zimbardo set up an entire "pretend prison" and assigned his subjects roles as prisoners or guards. Quite quickly, the guards went beyond simple play acting and actually took on the roles of sadistic bullies, exposing the prisoners to all kinds of rough and degrading treatment, while the prisoners resigned themselves to their fate or took on the roles of rebels. [11] More recently, Zimbardo has argued that his work sheds light on atrocities such as the torture at the Abu Ghraib prison in 2004, when US army guards were found to have tortured and degraded Iraqi prisoners under their guard in truly shocking ways.

5. Are you a slave to pleasure? (Olds and Milner, 1954)

Why do we do the things we do? Why do we eat or drink, play football, watch TV... or do the legions of other things we feel compelled to do each day? How, when we take these sorts of behaviors to extremes, do we become addicted to things like drink and drugs, gambling or sex? Are they ordinary pleasures taken to extremes or something altogether different? Obsessions, compulsions, and addictive behaviors are complex and very difficult to treat, but what causes them... and how do we treat them?

Artwork: A rat will happily stimulate the "pleasure centre" in its brain.

“ It appears that motivation, like sensation, has local centers in the brain. ” James Olds, Scientific American, 1956.

The Olds and Milner ICSS (intracranial self-stimulation) experiment was widely interpreted as the discovery of a "pleasure center" in the brain, but we have to take that suggestion with quite a pinch of salt. It's fascinating, but also quite reductively depressing, to imagine that a lot of the things humans feel compelled to do each day—from work and eating to sport and sex—are motivated by nothing more than the need to scratch a deep neural itch: to repeatedly stimulate a "hungry" part of our brain. While it offers important insights into addictive behavior, the idea that all of our complex human pleasure-seeking stems from something so crudely behavioral—stimulus and reward—seems absurdly over-simple. It's fascinating to search for references to Olds and Milner's work and see it quoted in books with such titles as Your Money and Your Brain: How the New Science of Neuroeconomics Can Help Make You Rich . But it's quite a stretch from a rat pushing on a pedal to making arguments of that kind. [14]

6: Are you asleep at the wheel? (Libet, 1983)

Being a conscious, active human being is a bit like driving a car: looking out through your eyes is like staring through a windshield, seeing (perceiving) things and responding to them, as they see and respond to you. Consciousness, in other words, feels like a "top-down" thing; like the driver of a car, we're always in control, willing the world to bend to our way, making things happen according to ideas our brains we devise beforehand. But how true is that really? If you are a driver, you'll know that much of what you do depends on a kind of mental "auto-pilot" or cruise control. As a practiced driver, you barely have to think about what you're doing at all—it's completely automatic. We're only really aware of just how effort-full and attentive drivers need to be when we first start learning. We soon learn to do most of the things involved in driving without being consciously aware of them at all—and that's true of other things too, not just driving a car. Seen this way, driving seems impressive—but if you think again about the Simons and Chabris gorilla experiment, and consider its implications for sitting behind the wheel, you might want to take the bus in future.

Still, you might think, you're always, ultimately, in charge and in control: you're the driver , not the passenger, even if you are sometimes dozy at the wheel. And yet, a remarkable series of experiments by Benjamin Libet, in the 1980s, appeared to demonstrate something entirely different: far from consciously making things happen, sometimes we become conscious of what we've done after the fact. In Libet's experiments, he made people watch a clock and move their wrist when it reached a certain time. But their brain activity (which he was also monitoring) showed a peak a fraction of a second before their conscious decision to move, suggesting, at least in this case, that consciousness is the effect, not the cause. [15]

“ Many of our mental functions are carried out unconsciously , without conscious awareness. ” Benjamin Libet, Mind Time, 2004, p.2.

On the face of it, Libet's work seems to have extraordinary implications for the study of consciousness. It's almost like we're zombies sitting at the wheel of a self-driving car. Is the whole idea of conscious free will just an illusion, an accidental artefact of knee-jerk behavior that happens much more automatically? You can certainly try to argue it that way, as many people have. On the other hand, it's important to remember that this is a highly constrained laboratory experiment and you can't automatically extrapolate from that to more general human behavior. (Apart from anything else, the methodology of Libet's experiments has been questioned. [16] ) While you could try to argue that a complex decision (to buy a house or quit your job) is made unconsciously or subconsciously in whatever manner and we rationalize or become conscious of it after the fact, experiments like Libet's aren't offering evidence for that. Sometimes, it's too much of a stretch to argue from simple, highly contrived, very abstract laboratory experiments to bigger, bolder, and more general everyday behavior.

On the other hand, it's quite likely that some behavior that we believe to be consciously pre-determined is anything but, as William James (and, independently, Carl Lange) reasoned way back in the late 19th century. In a famous example James offered, we assume we run from a scary bear because we see the bear and feel afraid. But James believed the reasoning here is back to front: we see the bear, run, and only feel afraid because we find ourselves running from a bear! (How we arrive at emotions is a whole huge topic of its own. The James-Lange theory eventually spawned more developed theories by Walter Cannon and Philip Bard, who believed emotions and their causes happen simultaneously, and Stanley Shachter and Jerome Singer, who believe emotions stem both from our bodily reactions and how we think about them.) [17]

7: Why are you so attached? (Harlow et al, 1971)

“ Love is a wondrous state, deep, tender, and rewarding. Because of its intimate and personal nature it is regarded by some as an improper topic for experimental research. ” Harry Harlow, 1958.

Artwork: Animals crave proper comfort, not just the simple "reduction" of "drives" like hunger. Photo courtesy of NASA and Wikimedia Commons .

There's an obvious evolutionary reason why we get attached to other people: one way or another, it improves our chances of surviving, mating, and passing on our genes to future generations. Attachment begins at birth, but our attachment to our mothers isn't motivated purely by a simple need for nourishment (through breastfeeding or whatever it might be). One of the most famous psychological experiments of all time demonstrated this back in the early 1970s. The University of Wisconsin's Harry Harlow and his wife Margaret tested what happened when newborn baby monkeys were separated from their mothers and "raised," instead by crude, mechanical surrogates. In particular, Harlow looked at how the monkeys behaved toward two rival "mothers", one with a wooden head and a wire body that had a feeding bottle attached, and one made from soft, warm, comforting cloth. Perhaps surprisingly, the babies preferred the cloth mother. Even when they ventured over to the wire mother for food, they soon returned to the cloth mother for comfort and reassurance. [18]

The fascinating thing about this study is that it suggests the need for comfort is at least as important as the (more obviously fundamental) need for nourishment, so busting the cold, harsh claims of hard-wired behaviorists, who believed our attachment to our mothers was all about mechanistic "drive reduction," or knee-jerk stimulus and response. Ultimately, we love the loving—Harlow's "contact comfort"—and perhaps things like habits, routines, and traditions can all be interpreted in this light.

8: Are you as rational as you think? (Wason, 1966)

“ ... I have concentrated mainly on the mistakes, assumptions, and stereotyped behavior which occur when people have to reason about abstract material. But... we seldom do reason about abstract material. ” Peter Wason, 1966.

Like everyone else, you probably have your moments of wild, reckless abandon, but faced with the task of making a calm, rational judgment about something, how well do you think you'd do? It's not a question of what you know or how clever you are, but how well you can make a judgment or a decision. Suppose, for example, you had to hire the best applicant for a job based on a pile of résumés. Or what if you had to find a new apartment by the end of the month and you had a limited selection to pick among. What if you were on the jury of a trial and had to sit through weeks or evidence to reach a verdict? How well do you think you'd do? Probably, given all the information, you feel you'd make a fair job of it: you have faith in your judgment. And yet, decades of research into human decision-making suggests you'll massively overestimate your own ability. Overconfident and under-informed, you'll jump to hasty conclusions, swayed by glaring biases you don't even notice. In the words of Daniel Kahneman, probably the world's leading expert on human rationality, your brain opts to think "fast" (reaches a quick and dirty decision) when sometimes it'd be better off thinking "slow" (reaching a more considered verdict). [25]

A classic demonstration of how poorly we think was devised by British psychologist Peter Wason in 1966. The experimenter puts a set of four white cards in front of you, each of which has a letter on one side and a number on the other. Then they tell you that if a card has a vowel on one side, it has an even number on the other side. Finally, they ask you which cards you need to turn over to verify if that statement is true. Suppose the cards show A, D, 4, and 7. The obvious answer, offered by most people, is A and 4 or just A. But the correct answer is actually A and 7. Once you've turned over A, it serves no purpose to turn over D or 4: turning over D tells us nothing, because it's not a vowel, while turning over 4 doesn't provide extra proof or disprove the statement. By turning over 7, however, you can potentially disprove the theory if you reveal a vowel on the other side of it. Wason's four-card test demonstrates what's known as "confirmation bias"—our failure to seek out evidence that contradicts things we believe. [19]

Artwork: Peter Wason's four-card selection test. If a card has a vowel on one side, it has an even number on the other. Which cards do you need to turn over to confirm this?

As with the other experiments here, you could extrapolate and argue that Wason's abstract reasoning test is echoed by bigger and wider failings we see in ourselves. Perhaps it goes some way to explaining things like online "echo chambers" and "filter bubbles", where we tend to watch, read, and listen to things that reinforce things we already believe—intellectual cloth mothers, you might call them—rather than challenging those comfortable beliefs or putting them to the test. But, again, a simple laboratory test is exactly what it is: a simple, laboratory test. And other, broader personal or social conclusions don't automatically follow on from it. (Indeed, you might recognize the tendency to argue that way as a confirmation bias all of its own.)

9: How do you learn things? (Pavlov, 1890s)

Learning might seem a very conscious and deliberate thing, especially if you hate the subject you're studying or merely sitting in school. What could be worse than "rote" learning your times table, practising French vocabulary, or revising for an exam? We also learn a lot of things less consciously—sometimes without any conscious effort at all. Animals (other than humans) don't sit in classrooms all day but they learn plenty of things. Even one of the simplest (a sea-slug called Aplysia californica ) will learn to withdraw its syphon and gill if you give it an electric shock, as Eric Kandel and James Schwartz famously discovered. [20]

“ The animal must respond to changes in the environment in such a manner that its responsive activity is directed toward the preservation of its existence. ” Ivan Pavlov, 1926.

So how does learning come about? At its most basic, it involves making connections or "associations" between things, something that was probed by Russian psychologist Ivan Pavlov in perhaps the most famous psychology experiment of all time. Pavlov looked at how dogs behave when he gave them food. Normally, he found dogs would salivate (a response) when he brought them a plate of food (a stimulus). We call this an unconditioned response (meaning default, normal, or just untrained): it's what the dogs do naturally. Now, with the food a distant doggy memory, Pavlov rang a bell (a neutral stimulus) and found it produced no response at all (the dogs didn't salivate). In the next phase of the experiment, he brought the dogs plates of food and rang a bell at the same time and found, again, that they salivated. So again, we have an unconditioned response, but this time to a pair of stimuli. Finally, after a period of this training, he tested what happened when he just rang the bell and, to his surprise, found that they salivated once again. In the jargon of psychology, we say the dogs had become "conditioned" to respond to the bell alone: they associated the bell with food and so responded by salivating. We call this a conditioned (trained or learned) response: the dogs have learned that the sound of the bell is generally linked to the appearance of food. [21]

Pavlov's work on conditioning was hugely influential—indeed, it was a key inspiration for the theory of behaviorism . Advanced by such luminaries as B.F. Skinner and J.B. Watson, this was the idea that animal behavior is largely a matter of stimulus and response and mental states—thinking, feeling, emoting, and reasoning—is irrelevant. But, as with all the other experiments here, it's a stretch to argue that we're all quasi-automated zombies raised in a kind of collective cloud of mind-control conditioning. It's true that we learn some things by simple, behavioural association, and animals like Aplysia may learn everything they know that way, but it doesn't follow that all animals learn everything by making endless daisy-chains of stimulus and response. [22]

10: You're happier than you realize (Seligman, 1975)

Money makes the world go round—or so goes the lyric of a famous song. But if you're American Martin Seligman, you'd probably think "happiness" was a better candidate for what powers the planet, or should. When I was studying psychology at college back in the mid-1980s, Professor Seligman came along to give a guest lecture—and it proved to be one of the most thought-provoking talks I would ever attend.

“ The time has finally arrived for a science that seeks to understand positive emotion, build strength and virtue, and provide guideposts for... 'the good life'. ” Martin Seligman, Authentic Happiness, 2003.

Though now widely and popularly known for his work in a field he calls positive psychology , Seligman originally made his name researching mental illness and how people came to be depressed. Taking a leaf from Pavlov's book, his subjects were dogs. Rather than feeding them and ringing bells, he studied what happened when he gave dogs electric shocks and either offered them an opportunity to escape or restrained them in a harness so they couldn't. What he discovered was that dogs that couldn't avoid the shocks became demoralised and depressed—they "learned helpnessness"—and eventually didn't even try to avoid punishment, even when (once again) they were allowed to. [23]

You can easily construct a whole (behavioural) theory of mental illness on the basis of Seligman's learned helplessness experiments but, once again, there's much more to it than that. People don't become depressed purely because they're in impossible situations where problems seem (to use the terminology) "internal" (their own fault), "global" (affecting all aspects of their life), and "stable" (impossible to change). Many different factors—neurochemical, behavioral, cognitive, and social—feed into depression and, as a result, there are just as many forms of treatment.

What's really interesting about Seligman's work is what he did next. In the 1990s, he realized psychologists were obsessed with mental illness and negativity when, in his view, they should probably spend more time figuring out what makes people happy. So began his more recent quest to understand "positive psychology" and the things we can all do to make our lives feel more fulfilled. The key, in his view, is working out and playing to what he calls our "signature strengths" (things we're good at that we enjoy doing). His ideas, which trace back to those early experiments on learned helpless in hapless dogs, have proved hugely influential, prompting many psychologists to switch their attention to developing a useful, practical "science of happiness." [24]

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For older readers, for younger readers, references ↑    see for example the classic discussion of consciousness in chapter 9: the stream of thought in principles of psychology (volume 1) by william james, henry holt, 1890. ↑    donald broadbent carried out notable early work on "selective attention" as this is called. see, for example, the role of auditory localization in attention and memory span by d.e. broadbent, j exp psychol, 1954, volume 47 number 3, pp.191–6. ↑     [pdf] gorillas in our midst: sustained inattentional blindness for dynamic events by daniel j simons, christopher f chabris, perception, 1999, volume 28, pp.1059–1074. ↑     the invisible gorilla and other ways our intuition deceives us by christopher chabris and daniel j. simons. harpercollins, 2010. ↑     [pdf] the effect of a pratfall on increasing interpersonal attractiveness by elliot aronson, ben willerman, and joanne floyd, psychon. sci., 1966, volume 4 number 6,pp.227–228. ↑     the 'tip of the tongue' phenomenon by roger brown and david mcneill, journal of verbal learning and verbal behavior, volume 5, issue 4, august 1966, pp.325–337. ↑     the cognitive neuropsychology of déjà vu by chris moulin, psychology press, 2017. ↑     reconstruction of automobile destruction: an example of the interaction between language and memory by elizabeth loftus and john palmer, journal of verbal learning & verbal behavior, volume 13 issue 5, pp.585–589. ↑     "that doesn't mean it really happened": an interview with elizabeth loftus by carrie poppy, the sceptical inquirer, september 8, 2016. ↑     behavioral study of obedience by stanley milgram, journal of abnormal and social psychology, 1963, volume 67, pp.371–378. ↑     a study of prisoners and guards in a simulated prison by craig haney, curtis banks, and philip zimbardo, naval research review, 1973, volume 30, pp.4–17. ↑     dr. robert g. heath: a controversial figure in the history of deep brain stimulation by christen m. o'neal et al, neurosurg focus 43 (3):e12, 2017. serendipity and the cerebral localization of pleasure by alan a. baumeister, journal of the history of the neurosciences, basic and clinical perspectives, volume 15, 2006. issue 2. the 'gay cure' experiments that were written out of scientific history by robert colvile, mosaic science, 4 july 2016. ↑     positive reinforcement produced by electrical stimulation of septal area and other regions of rat brain by j. olds and p. millner, j comp physiol psychol, 1954 dec;47(6):419–27. ↑     the pleasure areas by h.j. campbell, methuen, 1973. ↑     mind time: the temporal factor in consciousness by benjamin libet, harvard university press, 2004. ↑     exposing some holes in libet's classic free will study by christian jarrett, bps research digest, 2008. ↑    for a decent overview, see the section "theories of emotion" in 58: emotion in psychology by openstaxcollege. ↑     the nature of love by harry f. harlow, american psychologist, 13, pp.673–685. for a more general account, see love at goon park: harry harlow and the science of affection by by deborah blum, basic books, 2002. ↑     reasoning by p.c. wason, in foss, brian (ed.). new horizons in psychology. penguin, 1966, p.145. ↑     eric kandel and aplysia californica: their role in the elucidation of mechanisms of memory and the study of psychotherapy by michael robertson and garry walter, acta neuropsychiatrica, volume 22, issue 4, august 2010, pp.195–196. ↑     conditioned reflexes; an investigation of the physiological activity of the cerebral cortex by i.p pavlov. dover, 1960. ↑     pavlov's dogs by tim tully, current biology, 2003, volume 13, issue 4, 18 february 2003, pp.r117–r119. ↑     learned helplessness: theory and evidence by steven maier and martin seligman, journal of experimental psychology: general, 1976, volume 105, number 1, pp3.–46. ↑     authentic happiness by martin seligman, nicholas brealey, 2003. ↑     thinking fast and slow by daniel kahneman, penguin, 2011. ↑     subject reaction: the neglected factor in the ethics of experimentation by stanley milgram, the hastings center report, vol. 7, no. 5 (oct., 1977), pp. 19–23. please do not copy our articles onto blogs and other websites articles from this website are registered at the us copyright office. copying or otherwise using registered works without permission, removing this or other copyright notices, and/or infringing related rights could make you liable to severe civil or criminal penalties. text copyright © chris woodford 2021. all rights reserved. full copyright notice and terms of use . follow us, rate this page, tell your friends, cite this page, more to explore on our website....

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10 Cognitive Psychology Examples (Most Famous Experiments)

Dave Cornell (PhD)

Dr. Cornell has worked in education for more than 20 years. His work has involved designing teacher certification for Trinity College in London and in-service training for state governments in the United States. He has trained kindergarten teachers in 8 countries and helped businessmen and women open baby centers and kindergartens in 3 countries.

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Chris Drew (PhD)

This article was peer-reviewed and edited by Chris Drew (PhD). The review process on Helpful Professor involves having a PhD level expert fact check, edit, and contribute to articles. Reviewers ensure all content reflects expert academic consensus and is backed up with reference to academic studies. Dr. Drew has published over 20 academic articles in scholarly journals. He is the former editor of the Journal of Learning Development in Higher Education and holds a PhD in Education from ACU.

Cognitive psychology is the scientific study of mental processes. This includes trying to understand how people perceive the world around them, store and recall memories, acquire and use language, and engage in problem-solving.

Although not the first to study mental processes, Ulric Neisser helped cement the term in the field of psychology in his 1967 book Cognitive Psychology .

He offered an elaborate definition of cognitive psychology, with key points quoted below:

“ The term cognition refers to all processes by which sensory input is transformed, reduced, elaborated, recovered, and used…Giving such a sweeping definition, it is apparent that cognition is involved in everything a human being might possibly do” (p. 4).

In the mid-20 th century, there was significant divide in psychology between behaviorism and cognitive psychologists.

The behaviorists, such as Skinner, argued that only observable phenomena should be studied. Since mental processes could not be observed, they could not be studied scientifically.

Neisser countered, stating that:

“Cognitive processes surely exist, so it can hardly be unscientific to study them” (p. 5).  

Cognitive Psychology Examples (Famous Studies)

1. the forgetting curve and the serial position effect.

The contributions of Hermann Ebbinghaus to cognitive psychology were so significant that his individual studies could consume all 10 examples in this article.

Some believe that his book Über das Gedächtnis (1902) “…records one of the most remarkable research achievements in the history of psychology” (Roediger, 1985, p. 519).

Two of his most influential discoveries on memory include: the forgetting curve and the serial position effect .

To make his research on memory scientific, he created a list of over 2,000 nonsense syllables (e.g., BOK, YAT). Using commonly used vocabulary words would be too heavily associated with meaning, but nonsense syllables had no prior associations.

By conducting testing on himself, he was able to eliminate numerous other variables that would result from using people with varied backgrounds, experiences, and mental acuities.

So, he would present himself with lists of nonsense syllables and then test his memory at various intervals afterward.

This led to the discovery of the forgetting curve : forgetting begins right after the initial presentation of information and continues to degrade from then on.

The serial-position effect is the tendency to remember the first and last items in a list more so than the items in the middle.

2. The Magical Number 7 

One of the most often cited papers in psychology was written by cognitive psychologist George Miller of Harvard University in 1956.

The paper did not describe a series of experiments conducted by Miller himself. Instead, Miller outlines the work of several researchers that point to the magical number 7 as the capacity of short-term memory.

He made the case that this capacity is the same no matter what form the stimuli takes; whether talking about tones or words.

He also suggested that information is organized in “chunks,” not individual bits. A word is just one chunk for a native speaker, but for someone learning the language, the word consists of several bits of information in the form of individual letters.

Therefore, the capacity of the native speaker is 7 words, but for the beginner, it may only be two, or just 7 letters.

Miller concludes the paper by making a point about the number 7 itself:

“And finally, what about the magical number seven? What about the seven wonders of the world, the seven seas, the seven deadly sins, the seven daughters of Atlas in the Pleiades, the seven ages of man, the seven levels of hell, the seven primary colors, the seven notes of the musical scale, and the seven days of the week?” (p. 96).

See Also: Short-Term Memory Examples

3. The Framing Bias 

Tversky and Kahneman (1981) discovered the framing bias , which occurs when a person’s decision is influenced by the way information is presented. 

A typical study involved presenting information to participants, but varying one or two words in how the information was described.

For example:

“Imagine that the U.S. is preparing for the outbreak of an unusual Asian disease, which is expected to kill 600 people. If Program C is adopted 400 people will die. [22 percent] If Program D is adopted there is 1/3 probability that nobody will die, and 2/3 probability that 600 people will die. [78 percent] Which of the two programs would you favor?” (p. 453).

Although both programs lead to the same mortality rate, most research participants preferred Program D.

As the researchers explain, “the certain death of 400 people is less acceptable than the two-in-three chance that 600 will die” (p. 453).

Moreover, the effects were far from trivial:

“They occur when the outcomes concern the loss of human lives as well as in choices about money; they are not restricted to hypothetical questions and are not eliminated by monetary incentives” (p.  457).

4. Schema: Assimilation and Accommodation 

Jean Piaget’s research in the 1950’s and 60’s on cognitive development had a profound impact on our understanding of children. He detailed the way in which children perceive and make sense of the world and identified the stages of that developmental sequence which we still follow today.  

According to Piaget, children develop a schema , usually defined as a mental framework that organizes information about a concept.

As the child grows and experiences the world, everything they encounter will be processed within that schema. This is called assimilation . When the schema is altered or a new schema is developed, it is called accommodation .

He conducted a great deal of his research by observing his own three children and taking excruciatingly detailed notes on their behavior.

During the sensorimotor stage (birth to 2 years old), Piaget highlights a milestone that demonstrates the infant is now exploring their environment with intent.

“…the definitive conquest of the mechanisms of grasping marks the beginning of the complex behavior patterns which we shall call “assimilations through secondary schemata” and which characterize the first forms of deliberate action” (Piaget, 1956, p. 88).

Although this milestone takes place in the sensorimotor stage, it is much more than a sensory experience. It is driven by intent, a purely cognitive construct.

Priming occurs when exposure to a stimulus has an effect on our behavior or how we respond to information presented subsequently. It can occur outside of conscious awareness.  

Priming affects how we process all kinds of information and is a widely used concept in marketing.

Meyer and Schvaneveldt (1971) were among the first to study priming.

They presented research participants with various pairs of associated words (Bread/Butter), unassociated words (Bread/Doctor), or nonwords.

The participants were instructed to indicate “yes” if both words were real words or “no” if one was not a real word.

The results revealed that participants were able to make this decision much faster when the pair of words were associated than when they were unassociated.

Although not conclusive and in need of further research, this pattern indicated that words that have strong connections in memory are activated more easily than words that are less connected.

Research since has identified numerous types of priming, including: perceptual, semantic, associative, affective, and cultural.

6. Semantic Memory Network and Spreading Activation

Further research on priming was conducted by Collins and Loftus (1975). Their studies led to more conclusive evidence that information is stored in a memory network of linked concepts.

When one concept is activated, that activation spreads throughout the network and activates other concepts.

The stronger the connection between concepts, the more likely one will activate the other. Eventually, the activation loses energy and dissipates.

Collins and Loftus provide a thorough explanation of the semantic memory network :

“The more properties two concepts have in common, the more links there are between the two nodes via these properties and the more closely related are the concepts…When a concept is processed (or stimulated), activation spreads out along the paths of the network in a decreasing gradient” (p. 411).

This research led to a more complete understanding of how information is stored and organized in memory. This has helped us understand a wide range of psychological phenomena such as how we form impressions of others and make decisions.

7. The ELM Model of Persuasion

Understanding how people form an attitude has been an area of study in cognitive psychology for more than 50 years.

Researchers Petty and Cacioppo (1986) formulated the Elaboration Likelihood Model (ELM) of persuasion to explain how message factors and personality characteristics affect attitude formation.

The ELM identifies two routes to persuasion: central and peripheral.

The central route to persuasion is activated when the message recipient engages in a critical analysis of the message content. This occurs when the message is about an issue considered important by the recipient.

In this scenario, a person will be persuaded by the quality of arguments in the message.

The central route results

“…from a person’s careful and thoughtful consideration of the true merits of the information presented…” (1986, p. 125).

The peripheral route to persuasion involves very little cognitive processing of the message content. This occurs when the issue is unimportant to the recipient.

In this scenario, a person will be persuaded by the status of the person expressing their opinion.

The peripheral route results from:

“…some simple cue in the persuasion context (e.g., an attractive source) that induces change without necessitating scrutiny of the true merits of the information presented” (p. 125).

Findings from ELM research apply to everything from product advertising, to public health campaigns, to political debate.

Go Deeper: The Six Types of Persuasion

8. The Bobo Doll Study

The Bobo Doll study by Albert Bandura in 1963 may be one of the most famous studies in psychology and a founding study for the social cognitive theory . It had a tremendous impact on society as well.

It took place at a time in the U. S. in which there was great concern and debate over the growing prevalence of violence depicted on television.

In the study, children watched a video of an adult either playing violently or not violently with a Bobo doll.

Afterwards, each child was placed in a room with a Bobo doll. Their behavior was carefully observed by trained raters.

Children that watched the violent video were more aggressive towards the doll than those that watched the non-violent video.

This type of study was among the first demonstrate the powerful effect of television on children’s behavior. It led to decades of research and intense debate throughout society.

9. Bystander Intervention: The First Study

In 1964 in New York City, late at night, a young woman was murdered just steps away from her apartment.

The newspapers reported that nearly 40 residents heard her pleas for help, but that no one actually did anything. That reporting has now been found to have many inaccuracies.

However, the story created a national debate about crime and helping those in need.

This was the impetus for a study conducted by Latané and Darley (1968) on “ the bystander effect .”

The methodology was simple. Over 60 college students at New York University were taken to individual rooms to discuss an issue via an intercom system.

The students knew that several people would be participating in the discussion simultaneously.

One “participant” spoke about their difficulties adjusting to college life and their medical condition which sometimes led to seizures. This was a pre-recorded script and included a part where the “participant” acted as if they were feeling physical distress. They eventually stopped communicating with the other participants.

The results revealed that:

“The number of bystanders that the subject perceived to be present had a major effect on the likelihood with which she would report the emergency. Eighty-five percent of the subjects who thought they alone knew of the victim’s plight reported the seizure before the victim was cut off, only 31% of those who thought four other bystanders were present did so” (p. 379).

This was the beginning of a long program of research that identified the decision-making steps that determine the likelihood of a bystander intervening in an emergency situation.

10. The Car Crash Experiment: Leading Questions

Dr. Elizabeth Loftus and her undergraduate student John Palmer designed a study in 1974 that shook our confidence in eyewitness testimony.

Research participants watched videos that depicted accidents between two cars. Afterward, participants were asked to estimate how fast the two cars were traveling upon impact.  

“How fast were the two cars going when they ______ into each other?”

However, the word in the blank varied. For some participants the word in the blank was “smashed” and for other participants the word was “contacted.”

The results showed that estimates varied depending on the word.

When the word “smashed” was used, estimates were much higher than when the “contacted” was used. 

This was the first in a long line of research conducted on how phrasing can result in leading questions that affect the memory of eyewitnesses.

It has had a tremendous impact on law enforcement interrogation practices, line-up procedures, and the credibility of eyewitness testimony .

Today’s article was about 10 famous studies in cognitive psychology. Ten is actually a low number given how many studies have had substantial impact on the field.

The studies described above include the famous work of Ebbinghaus, who used himself as a test subject. This entire article could have consisted of his work.

Also included above was just one study by Tversky and Kahneman. The two researchers have identified so many heuristics and cognitive biases that only choosing one was just unfair.

Two studies by Loftus were included because they were both groundbreaking: one in memory and the other in eyewitness testimony.

Of course, Bandura’s Bobo Doll study was included because of its fame and impact on public discourse.

The ELM model and the earliest study on bystander intervention were also included. Both have had profound impacts in not just our understanding about the given subjects, but have also had substantial practical applications in various professions and matters in real-life.

Bandura, A. (1977).  Social Learning Theory . Prentice Hall.

Bandura, A., Ross, D., & Ross, S. A. (1963). Imitation of film-mediated aggressive models. The Journal of Abnormal and Social Psychology, 66 (1), 3–11. https://doi.org/10.1037/h0048687

Ebbinghaus, H. (1902). Grundz Üge der Psychologic. Leipzig, Germany: von Veit.

Ebbinghaus, H. (1964). Memory: A contribution to experimental psychology (H. A. Ruger, C. E. Bussenius translators). New York: Dover.

Ebbinghaus, H. (1913). On memory: A contribution to experimental psychology . New York: Teachers College.

Kitchen, P., Kerr, G., Schultz, D., Mccoll, R., & Pals, H. (2014). The elaboration likelihood model: Review, critique and research agenda. European Journal of Marketing, 48 (11/12), 2033-2050. https://doi.org/10.1108/EJM-12-2011-0776

Loftus, E. F., & Palmer, J. C. (1974). Reconstruction of automobile destruction: An example of the interaction between language and memory. Journal of Verbal Learning and Verbal Behavior, 13 (5), 585–589.

Miller, G. A. (1956). The magical number seven plus or minus two: some limits on our capacity for processing information. Psychological Review , 63 (2), 81–97.

Neisser, U. (1967). Cognitive psychology . Englewood Cliffs, NJ: Prentice Hall.

Roediger, H. (1985). Remembering Ebbinghaus. PsycCRITIQUES, 30(7), 519-523.

Petty, R.E. & Cacioppo, J.T. (1986). The Elaboration Likelihood Model of persuasion. Advances in Experimental Social Psychology, 19 , 123-205. Doi: https://doi.org/10.1016/S0065-2601(08)60214-2

Piaget, J. (1956; 1965). The origins of intelligence in children . International Universities Press Inc. New York.

Tversky, A., & Kahneman, D. (1981). The framing of decisions and the psychology of choice .  Science ,  211 (4481), 453-458.

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Famous Experiments

The Most Influential Psychological Experiments in History

Saavedra and Silverman (button phobia)

Pozzulo et al. (line-ups)

Reviewed by Olivia Guy-Evans, MSc

Hölzel et al. (mindfulness and brain scans)

Hassett et al. (monkey toy preferences), jean piaget, behaviorism, neuroscience.

Jean Piaget's theory of cognitive development suggests that children move through four different stages of intellectual development which reflect the increasing sophistication of children's thoughts. Child development is determined by biological maturation and interaction with the environment.

Learn More: Piaget's Stages of Cognitive Development

Behaviorism is a theory of learning that states all behaviors are learned through interaction with the environment through a process called conditioning. Thus, behavior is simply a response to environmental stimuli.

Learn More: Behaviorist Approach in Psychology

Sigmund Freud (1856 to 1939) was the founding father of psychoanalysis, a method for treating mental illness and a theory that explains human behavior. His theories are clinically derived, based on what his patients told him during therapy.

Learn More: Sigmund Freud's Influence on Psychology

An approach is a perspective that involves certain assumptions about human behavior: the way people function, which aspects of them are worthy of study, and what research methods are appropriate for undertaking this study. The five major psychological perspectives are biological, psychodynamic, behaviorist, cognitive, and humanistic.

Learn More: Major Perspectives in Modern Psychology

Neuroscience is the branch of science concerned with studying the nervous system. It is a multidisciplinary field integrating numerous perspectives from biology, psychology, and medicine. It consists of several sub-fields ranging from the study of neurochemicals to the study of behavior and thought.

Learn More: What is Neuroscience?

Frequent Asked Questions

Is psychodynamic same as psychoanalytic?

The words psychodynamic and psychoanalytic are often confused. Remember that Freud’s theories were psychoanalytic, whereas the term ‘psychodynamic’ refers to both his theories and those of his followers, such as Carl Jung, Anna Freud, and Erik Erikson.

Learn More: Psychodynamic Approach

What is developmental psychology?

Developmental psychology is a scientific approach which aims to explain how thinking, feeling, and behavior change throughout a person’s life. A significant proportion of theories within this discipline focus upon development during childhood, as this is the period during an individual’s lifespan when the most change occurs.

Learn More: Developmental Psychology

What is Freud’s psychosexual theory?

Sigmund Freud proposed that personality development in childhood takes place during five psychosexual stages, which are the oral, anal, phallic, latency, and genital stages.

During each stage, sexual energy (libido) is expressed in different ways and through different body parts.

Learn More: Freud’s Psychosexual Stages of Development

What Is object permanence in Piaget’s theory?

Object permanence means knowing that an object still exists, even if it is hidden. It requires the ability to form a mental representation (i.e. a schema) of the object.

The attainment of object permanence generally signals the transition from the sensorimotor stage to the  preoperational stage of development .

Learn More: What Is Object Permanence According To Piaget?

What is the difference between a psychology and sociology?

Psychology studies the mind of an individual to understand human behavior and social and emotional reactions, whereas sociology looks beyond individuals and examines societal institutions and groups of people.

Learn More: Similarities and Differences Between Sociology and Psychology

Explore Famous Experiments

Fagen et al. (elephant learning)

Perry et al. 2015 (Personal Space)

Reviewed by Saul McLeod, PhD

Solomon Asch Conformity Line Experiment Study

Bandura's Bobo Doll Experiment on Social Learning

Van Ijzendoorn & Kroonenberg: Cultural Variations in Attachment

John Money Gender Experiment: Reimer Twins

Dement and Kleitman (1957)

Henry Gustav Molaison: The Curious Case of Patient H.M. 

Held and Hein (1963) Kitten carosel

Hawthorne Effect: Definition, How It Works, and How to Avoid It

Harry Harlow Theory & Rhesus Monkey Experiments in Psychology

Hofling Hospital Experiment (1966)

Hodges and Tizard (1989): Attachment Research Study

What Happened to Kitty Genovese

Konrad Lorenz: Theory of Imprinting in Psychology

Little Hans - Freudian Case Study

Little Albert Experiment (Watson & Rayner)

Little Peter, Cover-Jones (1924)

Mary Ainsworth: Strange Situation Experiment & Attachment Theory

Stanford Marshmallow Test Experiment

Loftus and Palmer (1974): Car Crash Experiment

Stanley Milgram Shock Experiment

Pavlov’s Dogs Experiment and Pavlovian Conditioning Response

Phineas Gage: His Accident and Impact on Psychology

Piliavin (1969) Subway samaritan Study

Serial Position Effect (Glanzer & Cunitz, 1966)

Rosenhan (1973) Experiment - 'On being sane in insane places'

Robbers Cave Experiment | Realistic Conflict Theory

10 Psychological Experiments That Could Never Happen Today

Nowadays, the American Psychological Association has a Code of Conduct in place when it comes to ethics in psychological experiments. Experimenters must adhere to various rules pertaining to everything from confidentiality to consent to overall beneficence. Review boards are in place to enforce these ethics. But the standards were not always so strict, which is how some of the most famous studies in psychology came about. 

1. The Little Albert Experiment

At Johns Hopkins University in 1920, John B. Watson conducted a study of classical conditioning, a phenomenon that pairs a conditioned stimulus with an unconditioned stimulus until they produce the same result. This type of conditioning can create a response in a person or animal towards an object or sound that was previously neutral. Classical conditioning is commonly associated with Ivan Pavlov, who rang a bell every time he fed his dog until the mere sound of the bell caused his dog to salivate.

Watson tested classical conditioning on a 9-month-old baby he called Albert B. The young boy started the experiment loving animals, particularly a white rat. Watson started pairing the presence of the rat with the loud sound of a hammer hitting metal. Albert began to develop a fear of the white rat as well as most animals and furry objects. The experiment is considered particularly unethical today because Albert was never desensitized to the phobias that Watson produced in him. (The child died of an unrelated illness at age 6, so doctors were unable to determine if his phobias would have lasted into adulthood.)

2. Asch Conformity Experiments

Solomon Asch tested conformity at Swarthmore College in 1951 by putting a participant in a group of people whose task was to match line lengths. Each individual was expected to announce which of three lines was the closest in length to a reference line. But the participant was placed in a group of actors, who were all told to give the correct answer twice then switch to each saying the same incorrect answer. Asch wanted to see whether the participant would conform and start to give the wrong answer as well, knowing that he would otherwise be a single outlier.

Thirty-seven of the 50 participants agreed with the incorrect group despite physical evidence to the contrary. Asch used deception in his experiment without getting informed consent from his participants, so his study could not be replicated today.

3. The Bystander Effect

Some psychological experiments that were designed to test the bystander effect are considered unethical by today’s standards. In 1968, John Darley and Bibb Latané developed an interest in crime witnesses who did not take action. They were particularly intrigued by the murder of Kitty Genovese , a young woman whose murder was witnessed by many, but still not prevented.

The pair conducted a study at Columbia University in which they would give a participant a survey and leave him alone in a room to fill out the paper. Harmless smoke would start to seep into the room after a short amount of time. The study showed that the solo participant was much faster to report the smoke than participants who had the exact same experience, but were in a group.

The studies became progressively unethical by putting participants at risk of psychological harm. Darley and Latané played a recording of an actor pretending to have a seizure in the headphones of a person, who believed he or she was listening to an actual medical emergency that was taking place down the hall. Again, participants were much quicker to react when they thought they were the sole person who could hear the seizure.

4. The Milgram Experiment

Yale psychologist Stanley Milgram hoped to further understand how so many people came to participate in the cruel acts of the Holocaust. He theorized that people are generally inclined to obey authority figures, posing the question , “Could it be that Eichmann and his million accomplices in the Holocaust were just following orders? Could we call them all accomplices?” In 1961, he began to conduct experiments of obedience.

Participants were under the impression that they were part of a study of memory . Each trial had a pair divided into “teacher” and “learner,” but one person was an actor, so only one was a true participant. The drawing was rigged so that the participant always took the role of “teacher.” The two were moved into separate rooms and the “teacher” was given instructions. He or she pressed a button to shock the “learner” each time an incorrect answer was provided. These shocks would increase in voltage each time. Eventually, the actor would start to complain followed by more and more desperate screaming. Milgram learned that the majority of participants followed orders to continue delivering shocks despite the clear discomfort of the “learner.”

Had the shocks existed and been at the voltage they were labeled, the majority would have actually killed the “learner” in the next room. Having this fact revealed to the participant after the study concluded would be a clear example of psychological harm.

5. Harlow’s Monkey Experiments

In the 1950s, Harry Harlow of the University of Wisconsin tested infant dependency using rhesus monkeys in his experiments rather than human babies. The monkey was removed from its actual mother which was replaced with two “mothers,” one made of cloth and one made of wire. The cloth “mother” served no purpose other than its comforting feel whereas the wire “mother” fed the monkey through a bottle. The monkey spent the majority of his day next to the cloth “mother” and only around one hour a day next to the wire “mother,” despite the association between the wire model and food.

Harlow also used intimidation to prove that the monkey found the cloth “mother” to be superior. He would scare the infants and watch as the monkey ran towards the cloth model. Harlow also conducted experiments which isolated monkeys from other monkeys in order to show that those who did not learn to be part of the group at a young age were unable to assimilate and mate when they got older. Harlow’s experiments ceased in 1985 due to APA rules against the mistreatment of animals as well as humans . However, Department of Psychiatry Chair Ned H. Kalin, M.D. of the University of Wisconsin School of Medicine and Public Health has recently begun similar experiments that involve isolating infant monkeys and exposing them to frightening stimuli. He hopes to discover data on human anxiety, but is meeting with resistance from animal welfare organizations and the general public.

6. Learned Helplessness

The ethics of Martin Seligman’s experiments on learned helplessness would also be called into question today due to his mistreatment of animals. In 1965, Seligman and his team used dogs as subjects to test how one might perceive control. The group would place a dog on one side of a box that was divided in half by a low barrier. Then they would administer a shock, which was avoidable if the dog jumped over the barrier to the other half. Dogs quickly learned how to prevent themselves from being shocked.

Seligman’s group then harnessed a group of dogs and randomly administered shocks, which were completely unavoidable. The next day, these dogs were placed in the box with the barrier. Despite new circumstances that would have allowed them to escape the painful shocks, these dogs did not even try to jump over the barrier; they only cried and did not jump at all, demonstrating learned helplessness.

7. Robbers Cave Experiment

Muzafer Sherif conducted the Robbers Cave Experiment in the summer of 1954, testing group dynamics in the face of conflict. A group of preteen boys were brought to a summer camp, but they did not know that the counselors were actually psychological researchers. The boys were split into two groups, which were kept very separate. The groups only came into contact with each other when they were competing in sporting events or other activities.

The experimenters orchestrated increased tension between the two groups, particularly by keeping competitions close in points. Then, Sherif created problems, such as a water shortage, that would require both teams to unite and work together in order to achieve a goal. After a few of these, the groups became completely undivided and amicable.

Though the experiment seems simple and perhaps harmless, it would still be considered unethical today because Sherif used deception as the boys did not know they were participating in a psychological experiment. Sherif also did not have informed consent from participants.

8. The Monster Study

At the University of Iowa in 1939, Wendell Johnson and his team hoped to discover the cause of stuttering by attempting to turn orphans into stutterers. There were 22 young subjects, 12 of whom were non-stutterers. Half of the group experienced positive teaching whereas the other group dealt with negative reinforcement. The teachers continually told the latter group that they had stutters. No one in either group became stutterers at the end of the experiment, but those who received negative treatment did develop many of the self-esteem problems that stutterers often show. Perhaps Johnson’s interest in this phenomenon had to do with his own stutter as a child , but this study would never pass with a contemporary review board.

Johnson’s reputation as an unethical psychologist has not caused the University of Iowa to remove his name from its Speech and Hearing Clinic .

9. Blue Eyed versus Brown Eyed Students

Jane Elliott was not a psychologist, but she developed one of the most famously controversial exercises in 1968 by dividing students into a blue-eyed group and a brown-eyed group. Elliott was an elementary school teacher in Iowa, who was trying to give her students hands-on experience with discrimination the day after Martin Luther King Jr. was shot, but this exercise still has significance to psychology today. The famous exercise even transformed Elliott’s career into one centered around diversity training.

After dividing the class into groups, Elliott would cite phony scientific research claiming that one group was superior to the other. Throughout the day, the group would be treated as such. Elliott learned that it only took a day for the “superior” group to turn crueler and the “inferior” group to become more insecure. The blue eyed and brown eyed groups then switched so that all students endured the same prejudices.

Elliott’s exercise (which she repeated in 1969 and 1970) received plenty of public backlash, which is probably why it would not be replicated in a psychological experiment or classroom today. The main ethical concerns would be with deception and consent, though some of the original participants still regard the experiment as life-changing .

10. The Stanford Prison Experiment

In 1971, Philip Zimbardo of Stanford University conducted his famous prison experiment, which aimed to examine group behavior and the importance of roles. Zimbardo and his team picked a group of 24 male college students who were considered “healthy,” both physically and psychologically. The men had signed up to participate in a “ psychological study of prison life ,” which would pay them $15 per day. Half were randomly assigned to be prisoners and the other half were assigned to be prison guards. The experiment played out in the basement of the Stanford psychology department where Zimbardo’s team had created a makeshift prison. The experimenters went to great lengths to create a realistic experience for the prisoners, including fake arrests at the participants’ homes.

The prisoners were given a fairly standard introduction to prison life, which included being deloused and assigned an embarrassing uniform. The guards were given vague instructions that they should never be violent with the prisoners, but needed to stay in control. The first day passed without incident, but the prisoners rebelled on the second day by barricading themselves in their cells and ignoring the guards. This behavior shocked the guards and presumably led to the psychological abuse that followed. The guards started separating “good” and “bad” prisoners, and doled out punishments including push ups, solitary confinement, and public humiliation to rebellious prisoners.

Zimbardo explained , “In only a few days, our guards became sadistic and our prisoners became depressed and showed signs of extreme stress.” Two prisoners dropped out of the experiment; one eventually became a psychologist and a consultant for prisons . The experiment was originally supposed to last for two weeks, but it ended early when Zimbardo’s future wife, psychologist Christina Maslach, visited the experiment on the fifth day and told him , “I think it’s terrible what you’re doing to those boys.”

Despite the unethical experiment, Zimbardo is still a working psychologist today. He was even honored by the American Psychological Association with a Gold Medal Award for Life Achievement in the Science of Psychology in 2012 .

Explore Psychology

Psychology Articles, Study Guides, and Resources

8 Classic Psychological Experiments

Psychological experiments can tell us a lot about the human mind and behavior. Some of the best-known experiments have given us insights into topics such as conformity, obedience, attachment, and learning. There are many famous (and sometimes infamous) psychological experiments that have helped shape our understanding of the human mind and behavior. Such experiments offered…

In this article

Psychological experiments can tell us a lot about the human mind and behavior. Some of the best-known experiments have given us insights into topics such as conformity, obedience, attachment, and learning.

There are many famous (and sometimes infamous) psychological experiments that have helped shape our understanding of the human mind and behavior. Such experiments offered insights into how people respond to social pressure and how they develop associations that lead to fear. 

While many of these psychological experiments are well known even outside of psychology, it is important to recognize that many of them could not be performed today.

In many instances, these experiments would never receive institutional review board approval due to ethical concerns and the potential harm to participants.

In this article, learn more about some of the most famous psychological experiments and discover why some of them are considered so controversial.

Pavlov’s Dog Experiments, 1897

While not set up as a psychological experiment, Ivan Pavlov’s research on the digestive systems of dogs had a tremendous impact on the field of psychology. During his research, he noticed that dogs would begin to salivate whenever they saw the lab assistant who provided them with food.

By pairing a previously neutral stimulus (a sound) with a naturally occurring stimulus that automatically produces a response (food), Pavlov discovered that he could condition the dogs to salivate when they heard the sound.

The discovery of the classical conditioning process played a pivotal role in the formation of the behavioral school of psychology and has continued to influence our understanding of how learning can occur through associations.

Little Albert Experiment, 1920

Anyone who has ever taken an introductory course in psychology is probably familiar with the Little Albert experiment. In the famous experiment conducted in the 1920s by behaviorists John B. Watson and Rosalie Rayner, an infant was exposed to a white rat to which he initially exhibited no fear. The researchers then presented the rat accompanied by a loud clanging noise. 

After repeated pairings, the child began to cry when the rat alone was presented. This fear was even generalized to objects that resembled the rat such as fluffy white toys.

Watson’s research played an important role in the development of the school of thought known as behaviorism . It also provided evidence of the power of classical conditioning , which involves learning by association. 

The findings also had implications for our understanding of how fears can form, including phobias and irrational fears that sometimes develop early in life or after a single frightening experience.

Asch Conformity Experiment, 1951

The Asch conformity experiments were a series of psychological experiments conducted by psychologist Solomon Asch during the 1950s. The purpose of the experiments was to determine how much a person’s opinions were influenced by the opinions of the rest of the group.

In the study, participants were told that they were taking a “vision test” along with several others. In reality, the other individuals in the room were actors who were following the experimenters’ instructions.

When shown several line segments, the participants were supposed to select the one that matched a sample line segment in length.

In some cases, those who were in on the study would pick the obvious match. In other cases, however, the study confederates would unanimously pick the wrong line segment. 

The results of Asch’s experiments found that people tended to conform when other people unanimously picked the wrong answer.

Across the 12 trials he conducted, Asch found that around 33% of the naive participants conformed to the group and picked the wrong answer. In a control group, for comparison, less than 1% of the participants ever chose the wrong answer. 

The experiments revealed how group pressure can cause people to change their own behavior in order to fit in with the rest of the group.

Robbers Cave Experiment, 1954

In the Robbers Cave psychological experiment , researcher Muzafer Sherif and his colleagues used a summer camp setting to look at how factors such as competition and prejudice influenced conflict between groups. 

In the experiment, boys attending a summer camp were randomly assigned to two groups. The groups were then placed in situations where they had to compete with one another. Such competition led to conflicts, competition, and hostility between the two groups.

Later, the experiments attempted to reconcile the groups and eliminate the tensions that the previous competitive tasks had created. Bonding activities had little impact, but the researchers found that situations that required members of the two groups to work together in order to overcome a problem were effective at reducing tensions.

The study had implications for how different social groups create their own norms and hierarchies and then use those rules to exclude outsiders.

Harlow’s Rhesus Monkey Experiments, 1958

Psychologist Harry Harlow conducted a series of experiments during the 1950s and 1960s that demonstrated how important love and affection were in the course of child development. In his experiments, he placed infant monkeys in an environment where they had access to two different surrogate “mothers.”

One was a wire mother who held a bottle and provided food, while the other was a soft surrogate mother who was covered in a terry cloth fabric. 

While the cloth mother did not provide nourishment, the experiments demonstrated that the baby monkeys preferred the soft mother over the wire mother. When they were frightened and needed comfort, they would turn to the cloth mother for security.

Milgram Obedience Experiment, 1963

The Milgram experiment was one of the most famous and controversial psychological experiments ever performed. The experiments involved an experimenter ordering participants to deliver electrical shocks to other people.

While the people who were supposedly receiving the shocks were actors who pretended to be in pain, the participants fully believed that they were delivering painful, and even dangerous shocks. 

Milgram’s findings suggested that up to 65% of the participants were willing to deliver potentially fatal shocks to another person simply because an authority figure ordered them to do so. 

Based on these findings, Milgram proposed that people were willing to follow orders from an authority figure if they think that person will take responsibility for the results and is qualified to give orders. 

Bobo Doll Experiment, 1961-1963

In this experiment, Albert Bandura investigated the effects of observational learning by having young children witness acts of aggression and then observing them to see if they copied the behavior.

Children in the study observed adults act aggressively toward a Bobo doll, a large inflatable doll resembling a bowling pin. When hit or kicked, the doll tips sideways and then returns to an upright position.

Bandura found that children who watched an adult act aggressively were more likely to imitate those behaviors later when they were allowed to play in a room with the Bobo doll.

The study played an important role in our understanding of social learning theory and how kids learn by watching others. 

Stanford Prison Experiment, 1971

In this infamous social psychology experiment, Philip Zimbardo set up a mock prison in the basement of the Stanford University psychology department and randomly assigned a group of 24 college students to either be guards or prisoners. 

The study was originally supposed to last for two weeks but had to be stopped after six days because participants reportedly became so immersed in their roles that they began to experience upsetting psychological effects. The results were believed to demonstrate the power that social roles and expectations can exert over a person’s behavior. 

The experiment is widely described in psychology textbooks and even became the subject of a feature film in 2015. 

More recent analysis has suggested that the experiment had serious design flaws, among other problems. In addition to the already problematic ethics of the study, analysis of the study’s records suggests that the experimenters may have played a role in encouraging the abusive behavior displayed by the participants.

Impact of Psychological Experiments

The psychology experiments of the past have had an impact on our understanding of the human mind and behavior. While many of the experiments described here have problems in terms of their design and their ethics, they remain some of the most famous examples of research within the field of psychology.

Learning more about these classic experiments can help you better understand research that informed the development of psychology. It can also provide inspiration for your own psychology experiment ideas and provide information to explore in your psychology papers .

Bandura A, Ross D, Ross SA. Transmission of aggression through imitation of aggressive models . Journal of Abnormal and Social Psychology. 1961;63:575-82. doi:10.1037/h0045925

Gantt WH . Ivan Pavlov . Encyclopaedia Brittanica . Updated February 23, 2020.

Gonzalez-franco M, Slater M, Birney ME, Swapp D, Haslam SA, Reicher SD. Participant concerns for the Learner in a Virtual Reality replication of the Milgram obedience study. PLoS ONE. 2018;13(12):e0209704. doi:10.1371/journal.pone.0209704

Jeon, HL. The environmental factor within the Solomon Asch Line Test . International Journal of Social Science and Humanity. 2014;4(4):264-268. doi:10.7763/IJSSH.2014.V4.360 

Le Texier T. Debunking the Stanford Prison Experiment . American Psychologist . 2019;74(7):823-839. doi:10.1037/amp0000401

Sherif M, Harvey OJ, White BJ, Hood WR, Sherif CW. Intergroup conflict and cooperation: The Robbers Cave experiment (Vol. 10) . Norman, OK: University Book Exchange; 1961.

Zimbardo P, Haney C, Banks WC, Jaffe D. The Stanford Prison Experiment: A simulation study of the psychology of imprisonment. Stanford University, Stanford Digital Repository, Stanford; 1971.

Editor-in-Chief

Kendra Cherry, MS.Ed., is a writer, editor, psychosocial therapist, and founder of Explore Psychology, an online psychology resource. She is a Senior Writer for Verywell Mind and is the author of the Everything Psychology Book (Adams Media).

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