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The Secrets Behind Psychology’s Most Famous Experiment

What you didn't know about the Milgram experiments.

If you were asked to name the most famous psychology investigation ever to be conducted, the chances are good that you’d come up with the “obedience to authority” experiment as your answer. From this study, you learned that ordinary people are capable of inflicting pain on their fellow humans if someone gives them orders to do so. Yet, in this fascinating new book, Behind the Shock Machine, we learn that the study, if not the conclusion, is highly flawed.

Even if you never took introductory psychology or even high school psychology, you must certainly have heard at some point in your life about this well-known investigation. A Yale psychologist brought ordinary citizens into his lab and instructed them to act as teachers, administering what they believed to be painful electric shocks when the “learner” failed at a simple memory task. In reality, of course, the situation was all a setup. The electric shock machine was a fake, the learner was hired by the experimenter to pretend to make the punishment-deserving mistakes, and the person acting as the experimenter was an actor hired by the psychologist. The psychologist, Stanley Milgram, was motivated by his reading of actions of Nazi concentration camp guards to find out if the tendency to obey authority (“I was only following orders”) was a general human trait or some specific feature of the German psyche.

Psychology students have, for the past 40 years or so, memorized the statistic that 65% of all participants in the Milgram experiments not only administered what they thought was an electric shock but went “all the way,” letting loose the maximum and potentially lethal dose in the face of the learner’s repeated mistakes. They’ve also learned that, as a result of much public outcry following the study’s publication, the American Psychological Association has enacted a set of stringent ethical guidelines that require research participants to be informed of a study’s purposes ahead of time, to be allowed to withdraw without penalty during the experiment if they don’t want to continue, and to receive a complete debriefing after the study ends explaining exactly what was done, and why.

Even though the Milgram study seemed to provide compelling evidence for the human tendency to exert cruel punishment while under orders, there were occasional reports questioning the validity of its findings. Many of these concerns were addressed by a replication study conducted by Santa Clara University psychologist Jerry Burger.

This study, the subject of a 2007 ABC 20-20 documentary, and published in 2009 in the prestigious journal American Psychologist, supported the finding that the majority of participants were willing to punish the learner by administering what they thought was a painful electric shock. However, the Burger replication differed from Milgram’s study in the important way that the maximum level of shock that “teachers” could administer was 150 volts, or 1/3 the amount used as the cutoff in the original studies.

For many in the psychological community, the Burger replication seemed to put to rest questions about whether the Milgram findings described something fundamental to the human psyche. We were safe again to teach our students and write our own scientific papers, confident that the general tendency to conform is something real in our social attitudes and behavior. The publication by Australian author and journalist Gina Perry of Behind the Shock Machine (2012) shatters that conclusion.

This 395-page book with its 21 pages of references documents in extensive detail the author’s journey to understand the purpose, findings, and interpretations of all 24 conditions of what we now know as “the” Milgram experiment. Perry spent months tracking down former participants, Milgram students, and relatives of the men who served as the experimenter and learners. In addition, she pored through volumes of archives, papers, and notes that up until now have received very little public (if not professional) attention. Perry provides enough of her personal observations to give the reader a sense of who she is and how the experience of writing the book affected her. However, her focus remains unswervingly on the science behind the study and the man behind the science. It’s a complex mixture of compelling drama, unexpected revelations, and just plain old good storytelling.

I’ve been reading this book over the past few months, thanks to Ms. Perry’s kindly sending me a copy for my review. At the time, the book was not available in the U.S., but luckily it now is. While reading it, I wondered how I could ever do it justice. I’ve decided to focus on these four themes:

1. Findings Not Generally Known

As I stated earlier, nearly everyone who teaches and/or learns about the Milgram experiments comes away with the figure “65%.” This was the percentage of teachers who, in one of the study’s conditions, administered the maximum amount of shock possible. It’s fairly well known, though, that many participants refused to go to that level, particularly in the conditions when the study participants felt less pressured to conform. For example, if the learner and the teacher were in the same room, fewer teachers moved up the shock scale to its maximum voltage. What is less well broadcasted is the fact that many participants sensed that the learner wasn’t really receiving any shock. The psychological term for this is “participant expectations.”

All human participants go into psychology experiments with a certain amount of skepticism about what the experimenter is up to, so as a result, their behavior doesn’t reflect what they would actually do in the real world. Many of Milgram’s participants believed it to be impossible that the prestigious Yale University experimenter would allow real harm to be inflicted on an experimental subject. Although Milgram claimed that 75% of his participants thought they were administering painful shocks, Perry’s re-analysis of the data showed that “It’s more truthful to say that only half of the people who undertook the experiment fully believed it was real, and of those, two-thirds disobeyed the experimenter” (p. 163). Furthermore, she argues that many of those who did administer the maximum amount of shock did so because they were confident the shock wasn’t real or that the experiment was an elaborate ruse.

Perry spoke to one of Milgram’s former research assistants whose own unpublished analysis led him to conclude that “in 18 of 23 conditions, those who wrote that they fully believed the learner was receiving painful shocks gave lower levels of shock than those who said they thought the learner was faking it” (p. 164).

2. Ethical Issues

Soon after completing his experiments, Milgram was investigated by the American Psychological Association for ethical violations in the treatment of his participants, primarily due to the lack of proper attention given to the phase of the experiment called “debriefing.” At the time, Milgram argued that he had “de-hoaxed” his participants, meaning that he had told them that the experiment had all been a “hoax.” However, as Perry reveals, Milgram didn’t completely reveal the purpose of the study to his participants nor did he comfort their ethical qualms about having supposedly inflicted pain on a fellow human. Not only that, but the authority figure in the room, the actor hired to portray the experimenter, didn’t offer his participants an opportunity to opt-out of the study. This is now a mandatory requirement of all human research.

If participants want to discontinue their involvement in the study, they must be allowed to do so without any penalty or question. Yet, for Milgram, participants were told that they had no choice but to continue. The transcripts that Perry examined showed numerous dialogues in which the experimenter pushed the participant well beyond the point that the participant was ready to walk out, even without receiving compensation. As stated by one participant: “The experiment is not going to require me to go on. You take the money back.” The experimenter told this participant that “You have no other choice but to continue” (p. 196).

The most chilling revelation of the book to me was what happened in “Condition 24.” This was the one that most people don’t know about when the teacher and learner were either related to each other, neighbors, or friends. Of all the conditions, this one produced the least amount of obedience. However, those who went even partway left with grave doubts about themselves and their personal ethics. Milgram stopped short of devising a condition in which wives and husbands would be asked to shock each other. However, he kept Condition 24 a secret. Perry’s theory was that “Milgram might have kept it secret because he realized that what he’d asked subjects to do in condition 24 would be difficult to defend.” In addition, the data contradicted the results he hoped to demonstrate in the study as a whole: “When people believed someone was being hurt—and it was someone close to them—they refused to continue” (p. 202). To include their data would have lowered the estimated 65% obedience even further than was already apparent in many of the study’s variations, further challenging the study's validity.

3. Lack of Theory

As disturbing as Milgram’s experiments were in terms of ethics, you might believe that they could be justified on the basis of the underlying theory; namely, the value of showing that people would obey an authority figure, particularly if that authority figure wielded “authority” in the lab. However, according to Perry, Milgram embarked on the study without making specific predictions ahead of time.

In the chapter “In Search of a Theory,” Perry tells us that Milgram submitted his results to scientific journals only to be met by the criticism that he had “no clear theory… and therefore the psychological processes leading up to the obedient act remain a mystery” (p. 244). If he was going to get the study published, he needed to come up with a theory. According to Perry, Milgram found his inspiration in such sources as the instructions he read while on an airplane in which passengers are told how to respond to an emergency, the words of Adolf Eichmann while he was on trial for his actions during the Holocaust, and a book that he had seen in a bookstore called “How to Train Your Dog to Obey.” Although the article eventually was accepted for publication, Milgram continued to experience problems receiving funding due to the theory deficit: “Without a theory, and without an explanation of why people behaved as they did, the research seemed to shed little light on obedience to authority” (p. 247).

4. Milgram the Man

Perry’s overall portrayal of Milgram suggests that this was an individual driven by the pettiest of petty concerns that often plague academics. He became enraged when his colleagues and his participants didn’t understand or appreciate what he was trying to do. The product of a tradition in social psychology that set up elaborate unnatural scenarios in which to observe human behavior, Milgram sought to out-do his mentors and colleagues and make a permanent name for himself by concocting an experiment that would go further than all the others that preceded it. He is described as vengeful and elitist, critical of his female and working-class participants.

When Milgram's work was challenged in print by psychologist Diana Baumrind, he eventually disregarded her comments as a “tempest in a teapot,” despite the fact that the objections she raised were seminal in leading to a revised code of ethics by the American Psychological Association. Similarly, he became infuriated by a playwright who, some years after the study was published, painted a less than complimentary portrait of him. Despite all this, Milgram seemed fixated on gaining as much publicity as possible from this research, keeping press reports from his articles at bay until he was able to publish his book.

Social psychology experiments are often based on a premise of deception, including sometimes elaborate schemes to see how participants react to unusual conditions, including the pressure to conform. Philip Zimbardo, the man behind the Stanford Prison experiment, created a scenario perhaps even more extreme and disturbing than Milgram’s, pitting college students against each other as fake prisoners and guards. Unlike Milgram, however, Zimbardo realized it was time to call the whole thing off, and his experiment was discontinued when the behavior of his participants got out of hand.

It was also surprising to me to learn that Milgram was denied tenure at Harvard University because we so often associate him with his work at Yale. In fact, he spent the final years of his career at the City University of New York. According to one of his former students, Fordham University psychologist Harold Takooshian, while at CUNY, Milgram engaged in teaching methods that pushed the envelope in ways similar to his research. For example, Takooshian reports that at the end of the semester, Milgram asked the students in his graduate seminar to grade each other’s performance, and then to turn in their grades. Much to their chagrin, Milgram then read out the grades that the students each gave each other. Imagine how this experience affected the students as individuals, not to mention as a cohort of classmates. Takooshian also reports that Milgram would occasionally burst out into song or spontaneously invent other types of in-class experiments that left the students in a state of bewilderment about their professor: “The only predictable thing about Milgram was his unpredictability” (p. 278).

Perry began her journey to understand the Milgram experiments because, like many psychology students, she was fascinated with the findings and what they implied about human nature. By the end, she realized how important it was to “question the stories we’ve been told” (p. 12).

While reading the book, I felt that I was taking my own journey of psychological discovery. Each page contained a new revelation that led me to question what I thought I knew not only about Milgram, but the field of social psychology in general. You don’t have to be a psych history buff to enjoy this book, but even if you casually follow psych news, you’ll almost certainly question the stories you’ve been told as well.

Perry’s in-depth analysis makes us think about we are so fascinated with this study, so many years after its completion. Television documentaries, works of fiction, and reality shows based on the premise of the Milgram experiments continue to draw millions of viewers. However, once we start to separate the fiction from the reality perhaps, like Perry, we will be able to trade our “admiration of Milgram for a better view of people” (p. 388).

Copyright Susan Krauss Whitbourne, Ph.D. 201


Burger, J. M. (2009). Replicating Milgram: Would people still obey today? American Psychologist, 64, 1-11.

Perry, G. (2012). Behind the shock machine. Melbourne, Australia: Scribe.

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