How Monsters are Made

What makes ordinary people do evil things? It was a question that long fascinated the psychologist Philip Zimbardo, who died in October. Zimbardo was best known for the controversial Stanford prison experiment, in which he created a simulated prison in the basement of a university building and recruited volunteers to act as prisoners and guards. This week, we explore how Zimbardo came to create one of psychology's most notorious experiments – and inadvertently became the poster child for the human weaknesses he was trying to study.

Speaker names marked ? are inferred from speaking time and the show’s known hosts — they are not voice-verified.

• 0:00Shankar Vedantam?

  Hey there, Shankar here with a quick note before we start today's show. I'm bringing Hidden Brain to the stage in San Francisco and Seattle in February 2025. I'll share seven psychological insights from the last decade of hosting Hidden Brain. Each insight has made my life better, and I think it will do the same for you. Please join me for an evening of science and storytelling. More information and a link to tickets is at hiddenbrain.org/tour. That's hiddenbrain.org/tour. All attendees receive one year's complimentary membership to the meditation and sleep app, Calm. Hope to see you there. Again, go to hiddenbrain.org/tour.

• 0:46Shankar Vedantam?

  This is Hidden Brain. I'm Shankar Vedantam.

• 0:50Shankar Vedantam?

  The biblical king Solomon is said to have constructed a religious edifice nearly 3,000 years ago. Accounts of the Temple of Solomon, largely drawn from the Hebrew Bible, say that Solomon placed an object of incalculable value within a windowless room of the temple. It was the Ark of the Covenant, a wooden chest decorated with gold. Inside it were tablets given to Moses by God, inscribed with the Ten Commandments. Remnants or artifacts from the temple have never been found.

• 1:29Shankar Vedantam?

  About 300 years ago, the Temple of Solomon became a subject of intense interest to a gifted mathematician in England. Isaac Newton came to believe that biblical accounts of the temple contain messages and clues that could be mathematically decoded. He also felt the temple's architecture contained geometrical secrets and a blueprint of human history. Based on his calculations and deductions, he predicted a major event in the 21st century, one that some people took to mean the end of the world as we know it.

• 2:02Shankar Vedantam?

  Even as he dabbled in what would now be considered the occult, Isaac Newton also famously revolutionized our understanding of the physical world. He came up with laws of physics that are still taught in high schools today. His contributions to mathematics, especially the science of calculus, are used on a daily basis in fields as diverse as space travel and epidemiology. How did the scientist who helped us understand the law of gravity come to believe he had special powers to decode scripture? Why did one of the most influential mathematicians in history spend so many years trying to turn base metals into gold?

• 2:42Shankar Vedantam?

  It's easy to say Isaac Newton was being brilliant when he was inventing calculus and foolish when he dabbled in the occult. The truth was that Isaac Newton saw both of these as forms of exploration. It's just that we know that one turned out to be right and the other turned out to be wrong. Today, we're going to tell you the story of another explorer. He was a psychologist who wanted to answer big questions. But in trying to do so, he dreamed up one of the most notorious experiments of the 20th century and inadvertently became the poster child for the human weaknesses he was trying to study.

• 3:21Speaker 01

  What I try to do is create evil. It's really studying evil from the inside out.

• 3:26Shankar Vedantam?

  The risks of exploration and the lessons of hindsight. This week on Hidden Brain.

• 3:38Shankar Vedantam?

  Support for Hidden Brain comes from Progressive. The mighty dollar. Once upon a time, it had a whole menu named after it. Now, no more. But $1 a day lets you add Progressive Renters Insurance to your auto insurance. Learn more at progressive.com. Progressive Casualty Insurance Company, affiliates and other insurers. Average premium cost based on Progressive Home data from 2025. Product and prices may vary by state.

• 4:10Shankar Vedantam?

  Support for Hidden Brain comes from Dell. This Black Friday, give a gift that goes beyond the box: the Dell XPS 13 laptop. It's the thinnest, lightest XPS laptop yet, with a long battery life, beautiful design, and powerful performance with Intel Core processors. Find perks like Dell Rewards, fast free shipping, and flexible financing. Head to dell.com/deals. That's dell.com/deals.

• 4:44Speaker 02

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• 5:17Shankar Vedantam?

  In February 1933, shortly after Adolf Hitler was appointed Chancellor of Germany, a fire broke out in the Reichstag Building, home to the German parliament. The Nazis cited the fire as proof that communists were planning a violent takeover of the country. The solution they proposed was to suspend the Constitution, declare emergency rule, and bring an end to civil rights. It paved the way for Adolf Hitler to become the dictator of Germany. A month after the Reichstag fire, a baby boy was born in the South Bronx to a family of Italian origin.

• 5:52Speaker 01

  My parents were second-generation Sicilian. My family background was: my grandfather was a barber, my other grandfather was a shoemaker. So it was really, you know, tradespeople.

• 6:03Shankar Vedantam?

  This is Philip Zimbardo. In time, he was to become one of the most influential psychologists of the 20th century. And much of his life's work would attempt to understand how Adolf Hitler and the Nazis came to transform the minds of ordinary Germans.

• 6:21Shankar Vedantam?

  But in 1933, Philip's family was not thinking about Nazi Germany. It was the height of the Great Depression. In the United States, nearly a quarter of all workers were unemployed. Some people were living in shanty towns while others were on the move, desperate to find work. In addition to coming from a poor family, Philip was prone to deadly illnesses.

• 6:43Speaker 01

  When I was a child, I was very sickly. In fact, I almost died from pneumonia and whooping cough at a time when there was no penicillin or sulfa drugs for contagious diseases. So I was hospitalized for six months. And kids around me all died, and I survived somehow. Resilience or hardiness, I'm not sure what.

• 7:12Shankar Vedantam?

  Young Philip wasn't seen as resilient or hardy by the other kids in his neighborhood. They looked at this kid, who had escaped a brush with death, and saw a weakling, someone who could be pushed around.

• 7:24Speaker 01

  When I came out of the hospital because I was really sick, I used to get beaten up all the time, also because I looked Jewish. And then I realized that the world is made up of leaders and followers, and followers are going to get beaten up. So I really, as a six, seven, 10-year-old kid, started trying to understand what was it about some kids who got to be leaders? And I think I figured out a kind of recipe. They were bigger, they were the first ones to talk up. They usually had to joke, they usually had a big, stronger guy backing them up. And they always gave the group some interesting activities.

• 8:03Shankar Vedantam?

  Philip was not yet a psychologist, but already, he was coming up with psychological theories about the world. In what was to become a hallmark of his future career, he came up with bold intuitive leaps to explain the world he saw. And even as he engaged in the rites and rituals of childhood, there was always a part of his mind that played the observer, that watched himself engage in those rites and rituals. Philip noticed there were things you had to do to become accepted into a group.

• 8:33Speaker 01

  In order to get into the gang, and the gang was the kids on the block, the newest kid had to physically fight the most recent kid who was in the gang, until one of you got a bloody nose. And I hated violence. I could see it's the stupidness of these kind of rituals.

• 8:49Shankar Vedantam?

  Philip also noticed how hierarchy worked in groups.

• 8:53Speaker 01

  Some kids give orders, some kids follow orders. And I thought, you know, typically, the orders they follow are stupid. But once you get used to that, it becomes a habit.

• 9:03Shankar Vedantam?

  If some kids were going to give stupid orders and some kids were going to follow them, Philip realized he much preferred to be in the first group. He decided he would study the tricks and techniques leaders used to get to the top. He set to work developing those habits.

• 9:18Speaker 01

  But it was really structuring situations, being the one that came up with a new idea to say, hey, marble season should be always boring. Why don't we do stickball? So essentially, it's coming up with the idea of what to do that other kids would say, yeah, that's interesting, let's do it.

• 9:35Shankar Vedantam?

  It worked. Philip shared his image as a sickly kid. He became an athlete, excelling in track, softball, and baseball. He was voted the most popular kid in his high school class.

• 9:49Shankar Vedantam?

  But there was another realm where Philip realized he could not outshine the competition. That's because the competition, when it came to being the smartest kid in class, was no competition at all. A kid named Stanley had run off with those honors, and there was absolutely no catching him.

• 10:05Speaker 01

  He won all the medals at graduation, so obviously, nobody liked him because we were all envious of him. But he was super smart and super serious.

• 10:15Shankar Vedantam?

  That Stanley was Stanley Milgram, who just happened to be another famous psychologist of the 20th century. What were the odds that Stanley Milgram and Philip Zimbardo would be classmates at the same high school in the Bronx?

• 10:32Shankar Vedantam?

  World War II had just ended a few years earlier, and the conflict was still fresh in everyone's minds. Philip and Stanley were fascinated and horrified by the Nazi regime's ability to mobilize the German people. How had Adolf Hitler managed to get ordinary Germans to join in the mass extermination of millions of people?

• 10:52Shankar Vedantam?

  Stanley Milgram found it unsettling how easily the Nazis managed to associate large groups of people with being inherently different and inferior.

• 11:00Speaker 01

  He was worried that the Holocaust could happen again in America. And everybody said, Stanley, that was Nazi Germany. That was then, we're not that kind of people. And he would say, I'll bet they thought the same thing. And the bottom line, he says, how do you know how you would act unless you're in the situation? Because we all think we're good people.

• 11:17Shankar Vedantam?

  We all think we're good people. And yet, our circumstances can prompt us to do things we might never anticipate. Philip felt that good kids were not always good and bad kids were not always bad. It was the situation that made them what they were.

• 11:34Speaker 01

  If you're middle class, you don't do things for money because your parents give you the money. And if you're poor, nobody's going to give you things. So if you want to buy sneakers, then somebody comes on the corner and says, hey, carry this package down the other and give it to some guy named Charlie. Well, you knew it had to be something illegal because they're going to give you $10 to carrying a package down the street. But you also knew that if you got caught, there would be consequences. And I was tempted. I could use $10. I mean, you know, I used to work in a laundry truck, you know, delivering laundry in Harlem. I think we got $2 a day or something. So the temptation is always there.

• 12:12Shankar Vedantam?

  This, of course, is the central claim of the field of social psychology. Our behavior is not just about who we are as people. It's a product of who we are as individuals and the situations in which we find ourselves. Stanley Milgram went on to become a psychologist at Yale. Philip Zimbardo became a psychologist at Stanford. As they began their research careers, both men continued to circle the same questions they had asked one another as teenagers. Can you get good people to do terrible things? Are all humans pliable under the right conditions? Do we all have inner monsters just waiting for the right circumstances to be unleashed?

• 12:56Speaker 03

  Under what conditions would a person obey authority who commanded actions that went against conscience? These are exactly the questions that I wanted to investigate at Yale University.

• 13:07Shankar Vedantam?

  This is Stanley Milgram in a documentary he later produced about his work. In 1961, he began a series of experiments on obedience. The experiments were set up as a way for one volunteer to help improve the memory of another volunteer. A person in the role of a learner was given a list of items they had to remember. They would then recite the list to a volunteer who was asked to play the role of teacher. The person running the study told the teacher that every time the learner got an answer wrong, the teacher had to punish the learner by administering an electric shock.

• 13:42Speaker 01

  The brilliance of the experiment is that the teacher is sitting in front of a shock box with 30 switches. The first switch is only 15 volts. When you press a button, the learner who's in another room experiences some minimal level of shock. And then of the 30 switches, the increment is 15 volts, 15, 30, 45, etc. And the person doesn't respond until it gets up to nearly 100. But the problem is that you are now on a slippery slope down. So each increment is not noticeable from the previous. And so now, when you hit 100 and the guy starts to say, hey, that really hurts, you're only slightly different from where you were.

• 14:24Speaker 01

  And at some point, you realize you should have stopped sooner.

• 14:28Shankar Vedantam?

  We talked about this experiment at length in an episode of Hidden Brain titled, "The Influence You Have." No one was actually being shocked in the experiment. The learner was actually an actor working with Stanley Milgram. But the experiment unsettled people. That's because large numbers of volunteers who were playing the role of the teacher seemed perfectly willing to administer electric shocks that were ostensibly lethal enough to kill the learner. When the psychologists later debriefed some of the volunteers, they explained why they had followed orders. Why didn't you stop anyway? I did stop.

• 15:02Speaker 04

  But he kept going, keep going.

• 15:05Speaker 03

  But why would you just disregard what he said?

• 15:08Speaker 04

  He says it's got to go on, the experiment.

• 15:14Shankar Vedantam?

  Stanley Milgram's obedience studies made him famous well beyond the bounds of psychology classrooms and academic conferences. Across the country at Stanford, Philip Zimbardo was also developing the idea for a psychology experiment. It would be so audacious, so controversial, that it would generate even more shockwaves than the work of his former classmate.

• 15:36Speaker 05

  Prisoners must report all rule violations to the guards. Prisoners must report all rule violations to the guards.

• 15:43Shankar Vedantam?

  Coming up, how Philip Zimbardo came to create the infamous Stanford Prison Experiment. You're listening to Hidden Brain. I'm Shankar Vedantam.

• 15:53Speaker 05

  May result in punishment. May result in punishment. Result in? Punishment. Higher note. Again.

• 16:10Shankar Vedantam?

  Support for Hidden Brain comes from Progressive, the mighty dollar. Once upon a time, it had a whole menu named after it. Now, no more. But $1 a day lets you add Progressive Renters Insurance to your auto insurance. Learn more at progressive.com. Progressive Casualty Insurance Company, affiliates and other insurers. Average premium cost based on Progressive Home data from 2025. Product and prices may vary by state.

• 16:42Shankar Vedantam?

  Support for Hidden Brain comes from Quince. The best pieces in your closet are the ones you can count on, whether you're heading to work, going out, or keeping things casual. And this time of year, Quince makes finding something great for everyone else just as easy. Quince focuses on high-quality staples made with premium materials like 100% Mongolian cashmere, 14-karat gold, and Italian leather. All timeless, versatile pieces that feel special to unwrap and become everyday favorites long after the holidays. Give the gift of quality this holiday season. Download the Quince app for app-exclusive offers or go to quince.com. Get free shipping on your order and 365-day returns.

• 17:26Shankar Vedantam?

  Now available in Canada and the UK, too. And when Quince asks where you heard about them, let them know it was Hidden Brain. This is Hidden Brain. I'm Shankar Vedantam. It was the summer of 1971. The Vietnam War was grinding on, as were increasingly large protests against it. The New York Times had begun publishing excerpts from the Pentagon Papers. The cult leader Charles Manson was behind bars, recently convicted of first-degree murder and conspiracy to commit murder.

• 18:08Shankar Vedantam?

  It was a time of disruption and unrest, a time when Americans were feeling uneasy about their leaders and their nation's role in the world. Many young people in particular had the sense that the United States had gone astray and lost its moral compass. It was against this backdrop that Philip Zimbardo put an ad in newspapers in Palo Alto, California. He was looking for male college students to volunteer for a study. It was designed to understand how the roles we play shape how we behave.

• 18:45Speaker 01

  Who we are is really shaped not so much by somebody telling you what to do and not to do. It's really that we play roles. We're a student, we're a teacher, we're a worker. And those roles are always in some setting. And within those, you belong to some subgroups. Initially, you're with the new workers, you're with the freshmen and so forth. And I said, so that's where we really want to study how power operates.

• 19:09Shankar Vedantam?

  He started to think about various scenarios where people play highly specific roles and have varying degrees of power.

• 19:17Speaker 01

  I said, well, what kind of setting could we use to illustrate that? Now, you could have done a summer camp. In fact, since I did my experiment, many people have written to me, saying, oh, my god, I was in a summer camp where the counselors were brutal guards. But I thought prison, because prisons are all about power.

• 19:34Shankar Vedantam?

  Prison. What Phil had in mind was not to study how prisons operate in a state like California, but something much more audacious. He wanted to build his own prison. In the basement of Stanford University's Psychology Department, Phil and his colleagues created prison cells, complete with bars, each designed to hold three people. A corridor served as the prison yard. A closet was set aside for prisoners who were to be confined to solitary confinement. For two weeks, Phil announced, they would simulate a prison that would run 24 hours a day. Half the volunteers would play the role of prisoners, and half would play the role of prison guards. They sifted through about 75 applications they'd received

• 20:18Shankar Vedantam?

  from young men who were interested in the study. It wasn't difficult to pick volunteers, except for one problem. No one wanted to play the role of a prison guard.

• 20:27Speaker 01

  It's 1971. These are anti-war activists. These are civil rights activists. There's a hip, everybody's got hair down to here. Not only long hair, and nobody wanted to be a guard. Guards are pigs. I didn't go to college to become a prison guard.

• 20:44Shankar Vedantam?

  Phil says the research team ended up flipping a coin to determine who would be guards and who would be prisoners. The day before the experiment began, he gathered the volunteers who had been chosen as guards for an orientation. Phil had decided that he himself would play the role of prison superintendent. An undergraduate research assistant would be the warden. Phil told the guards that they weren't allowed to physically harm the prisoners, but they were given broad latitude to maintain order.

• 21:12Speaker 01

  We want them to own the prison, okay? And so what it means is, we go with them to buy uniforms in Army-Navy stores. They have military kind of uniform. We give them symbols of power, handcuffs, billy clubs, whistles. And then I imposed an interesting subtle piece from the movie Cool Hand Luke, namely, everybody, when they were in contact with the prisoners, had to wear silver reflecting sunglasses, which means that nobody can see your eyes.

• 21:45Shankar Vedantam?

  I want to stop here for a moment to note how unusual all of this was and how unthinkable it would be to run an experiment like this today. Phil did not have a host of administrators looking over his shoulder, making sure he didn't cross the line. From a scientific standpoint, he was simultaneously playing both researcher and participant. He was the prison superintendent and also the person who was supposed to be dispassionately studying how the prison operated. The theatricality of the experiment was no accident. Phil was an impresario, and he loved being the center of attention. One student who took an introductory psychology class at Stanford in the 1970s told me that Phil showed up on the first day wearing a long, black cape.

• 22:29Shankar Vedantam?

  The professor stood before the slack-jawed students, swept his cape 360 degrees around him like a magician, and intoned, "Welcome to psychology." Others remembered Phil would wear that cloak on his travels, including when he went through airports. With his piercing eyes and flamboyant style, I bet he looked every part the wizard. To make the drama really pop for his prison experiment, Phil even involved the Palo Alto Police Department. Again, zero chance this happens today.

• 23:04Speaker 01

  I recruited the Palo Alto Police Department, the real police department, to make simulated arrests, to go to each kid's place, ask for the name of the kid, and then give them their Miranda rights. You have a right to remain silent, right for lawyer. And then bring them down to where the squad car is with lights flashing, lean them against the car, handcuff them, give them their rights again. And again, neighbors and everybody's looking around.

• 23:34Shankar Vedantam?

  The police then took the students to the real police station to be fingerprinted and have their mug shots taken. They then put a blindfold on them and had them wait in a cell. If all of this wasn't bad enough, what happened next was truly shocking.

• 23:49Speaker 01

  Then my graduate students came, took the prisoners, put them in their car, took them down to our prison, and they stripped them naked. And when they take off the blindfold, the kid is standing naked and all the guards are around laughing, mocking him and say, "Welcome to the Stanford jail."

• 24:09Shankar Vedantam?

  The prisoners were given smocks and flip flops. They were each assigned numbers that were sewn onto their clothing.

• 24:15Speaker 01

  And they all had an iron chain and a lock on one ankle that was there all the time. And instead of cutting their hair, they wore women's nylon stocking caps. So it was really de-individuation, dehumanization.

• 24:31Shankar Vedantam?

  By the end of the first day, the experiment wasn't going as Phil thought it would. He briefly considered shutting it down, not because he had qualms about what he had put his volunteers through, but because the young men playing the role of guards refused to embrace their roles.

• 24:46Speaker 01

  The kids playing the role of guards just felt awkward. In fact, you can hear, we videotaped a lot of it. And they say, "Come on, you guys, stop laughing. This is serious business." But nobody could take it seriously.

• 24:55Speaker 05

  Everyone feels fine, so let's hear everyone say, "Mr. Correctional Officer, I feel fine." Mr. Correctional Officer, I feel fine. Mr. Correctional Officer, I feel fine.

• 25:06Shankar Vedantam?

  Phil decided to keep the experiment going. Early in the morning on day two, the prisoners revolted after being woken by guards blasting whistles and ordering them out of their cells for drugs.

• 25:17Speaker 05

  Come on, come on. Go. Go. Out. Come on, out.

• 25:22Speaker 01

  They ripped off their stocking caps, they ripped off their numbers, they barricaded themselves in their cell. And then they made a huge mistake. They started ridiculing the guards. Like, "You little punk, when I get up, I'm gonna kick your butt." And suddenly, the guards come to me and say, "What are we gonna do?" I said, "It's your prison. What do you want to do?" They said, "We need reinforcements." So it means there are three guards on the morning shift. They call in all the other guards. The guards meet, they have a meeting, say, "Okay, we gotta treat force with force." So they break down the doors, they drag the prisoners out, they strip them all naked.

• 25:56Speaker 01

  They put the ring leaders of rebellion in solitary confinement. Suddenly, they say, "These are dangerous prisoners."

• 26:04Shankar Vedantam?

  These are dangerous prisoners.

• 26:15Speaker 01

  That's the switch. They're no longer college students like you. And everybody knows they're college students. So now, they are dangerous prisoners. And what do you do with dangerous prisoners? You have to teach them that they have no power. They have minus power. Because the potential for rebellion is always there. And this is true of real guards in real prisons.

• 26:34Shankar Vedantam?

  How do you convey to prisoners that you hold all the power and they hold none?

• 26:39Speaker 01

  So, in every way and every day, you have to suppress their freedom, suppress their likelihood to rebel. And you had to demonstrate, mostly by doing arbitrary, stupid things, that you had power. So you tell a joke and they laugh, you punish them. They tell a joke and they don't laugh, you punish them. So you create a totally arbitrary environment where prisoners, college students, have no idea what to do.

• 27:04Shankar Vedantam?

  Years later, Phil will be called in to help understand the behavior of US guards at the Abu Ghraib prison in Iraq. Young American service members sadistically humiliated Iraqi prisoners and pretended they were going to electrocute them. They stripped prisoners naked, threatened them with snarling dogs, and laughed and took photos as prisoners screamed in terror.

• 27:30Shankar Vedantam?

  At the Stanford prison, some prisoners were denied bathroom breaks and were forced to use buckets as toilets.

• 27:36Speaker 01

  And then punishment is usually just push-ups, jumping jacks. But then it escalates. And it always escalates, as we saw in Abu Ghraib, toward the sexual. So the guards say, "You're Frankenstein, you're Mrs. Frankenstein. Walk like Frankenstein." And hug them, say, "I love you."

• 27:55Speaker 01

  And then little things like this, or, you know, your female camels, your male camels, bend over now, you know, hump them. So it's a play on words. And they're simulating sodomy in an experiment with college students. Now, some of this I didn't see because the experiment's going on 24 hours a day. And most of the things that, the worst things happen at night.

• 28:15Shankar Vedantam?

  The guards separated their captives into good prisoners and bad prisoners, those who were compliant and those who rebelled.

• 28:23Speaker 05

  Prisoners must report all rule violations to the guards. Prisoners must report all rule violations to the guards. Again. Prisoners must report all rule violations to the guards. Anybody who obey any of the above rules may result in punishment. Anybody who obey any of the above rules may result in punishment.

• 28:48Shankar Vedantam?

  As the days passed, a few prisoners requested to be released from the experiment and were allowed to leave. On the third day of the experiment, those who remained were allowed short visits from parents and friends. Two days later, in the evening, another visitor came to the jail, a graduate student named Christina Maslach. She was also Phil's girlfriend. What she saw appalled her.

• 29:12Speaker 01

  She sees something which, from her point of view, is unimaginable, that should happen anywhere. Unimaginable should happen in an experiment, namely, guards are cursing and screaming, pushing prisoners. Prisoners have bags over their head, they're shuffling their legs, legs are chained, it's like a chain gang. It's like, you know, like you see in pictures of the South, in, you know, in Louisiana prisons. And I'm looking at this, and literally, I have, I have eight o'clock breakfast, you know, 10 o'clock parole board hearing, 12 o'clock, and it's 10 o'clock, and it simply says, "Toilet run."

• 29:45Shankar Vedantam?

  What Christina saw as a dehumanizing abuse of power, Phil, in his role as prison superintendent, saw as a toilet run. In other words, it was simply time to check off an item on his bureaucratic to-do list.

• 29:58Speaker 01

  I look up and I put a checkmark. So what I'm seeing is nothing more than an administrative checkmark. So I am now in the mentality of a prison superintendent, which is the mentality of an administrator. And she's looking at this as a person with feelings. She had been a student, she's about to be a professor, and she sees this as horrific.

• 30:23Shankar Vedantam?

  Christina started to cry and fled outside with Phil at her heels.

• 30:37Speaker 01

  And now we're standing outside in the fresh air. It's now 11 o'clock at night, or 10:30 at night, in front of the psychology building. And she's saying, "How could you see what I see and not get upset?" And I'm saying, "What do you see?" It's the dynamics of human nature. It's the power of the situation. I'm giving all the psychological jargon, and she's giving me the humanity of the situation. "Boys are suffering. They're not prisoners." That's what she's saying. "They're not prisoners, they're boys, and you're responsible. How could you allow this to happen?"

• 31:12Shankar Vedantam?

  They stood there in the California night, and a gulf grew between them.

• 31:18Speaker 01

  She says, "I don't understand. I know you from other situations. You're a caring, loving professor. You love students, students love you. How could you see this? There's this chasm between us. I'm over here, and we're looking at the same thing, and we see two totally different worlds." And then she says, "I'm not sure I want to continue my relationship with you if this is the real you. I thought you were someone else when I started dating you, and I don't know who this is." So that's the ultimate power of situational transform. She's looking at me, and she knew me for a number of years as a professor there, and she's looking at me and saying, "I don't know who you are." And really, what she's saying, do you know who you are? And the answer is no. That this is, what I had become is abhorrent. I mean, I fight authoritarianism.

• 32:01Speaker 01

  I fight, you know, I'm as liberal as most people get. I'm anti-authoritarian, anti-control, anti-structure, all these things. And that's what I became. I mean, I became my worst inner enemy. And at that point, I just stopped. I mean, I think it's when she said, I'm not sure I want to continue my relationship. It was like a double slap in the face. I said, oh, my God, what's happened to me? It was really like, she should have just shook me and said, wake up. Yeah, the dream is over. The game is over.

• 32:33Shankar Vedantam?

  In a theatrical irony even he could not have devised, Phil had demonstrated in his own behavior what he hoped his experiment would demonstrate to others. He had become so caught up in the roles he was playing, the swashbuckling scientist, the prison superintendent, the high wizard of psychology, that he had lost track of his own values. Six days after it started, the Stanford Prison Experiment was over. But before the volunteers could leave, Phil interviewed them.

• 33:03Speaker 01

  Then we had all the prisoners come together to debrief. We spent hours, then all the guards separately, and then the prisoners and guards. Because I used that as moral reeducation, because I could say, we all did bad things, including me. What do we learn from this? We learn about the power of the situation. We learn to be aware of how easy each of us can get seduced into a role.

• 33:25Shankar Vedantam?

  He followed up again weeks later with the volunteers and asked the prisoners if they thought they would have behaved like the guards if the roles had been reversed.

• 33:32Speaker 01

  They said, I don't know. I probably would have played by the rules, but I would not have been as creative. That the worst guards were the ones who clearly went beyond the rules. That is, it was clear what you had to do to be a guard. And it was going beyond the boundary of your role. That in every role is a moral latitude. And clearly, some guards went beyond it. You know, you could say, do 10 push-ups, do 10 more. But then to tell somebody to sit on your back when you're doing push-ups. That's going beyond the thing. You know, to tell somebody to kiss the other guy as the bride of Frankenstein. That's being creatively evil. So again, most of the prisoners said, I'm either, I'm not sure what I would do.

• 34:13Speaker 01

  But I would be, I would be a guard who played by the rules and not create, not develop new rules.

• 34:27Shankar Vedantam?

  Phil's study sparked intense public interest and criticism, both of which have continued to this day. For starters, there was the inhumane treatment of the volunteers playing the role of prisoners, the decision to strip them naked, the physical punishments and verbal abuse, the restricted access to toilet facilities. Both the Stanford Prison Experiment and Stanley Milgram's obedience studies prompted universities to create more rigorous review processes before greenlighting experiments. I think it's impossible any review board at any major university today would greenlight a study like the Stanford Prison Experiment. In addition to the ethical concerns, scholars have also criticized the experiment as bad

• 35:12Shankar Vedantam?

  science or not really science at all. Some have argued that the guards were essentially primed to be abusive. As Phil noted earlier, the guards were given to understand the prison was theirs and that they should do what was needed to maintain order. They were arguably being nudged to amp up their behavior to please the researchers. Remember how Phil almost shut the experiment down the first day because nothing much was happening? The guards may well have picked up on that, a possibility confirmed recently by volunteer Dave Eschelman, who played a guard known for being particularly aggressive to the prisoners. He was interviewed for a documentary film titled "The Stanford Prison Experiment: Unlocking the Truth."

• 35:54Shankar Vedantam?

  Dave says he thought the experiment was designed to show that prisons were terrible. He believed his role was to provide proof.

• 36:01Speaker 06

  Proof that prisons are an evil environment. Given the times and given the fact we were students and very anti-establishment, we would have done anything to prove that this prison system was an evil institution. We were happy to play that role.

• 36:19Shankar Vedantam?

  For his part, Phil Zimbardo continued to defend the Stanford Prison Experiment for the rest of his very long career. He felt the question he was trying to answer was a vital one, and the best way to do so was to see how people responded to a situation in the real world in real time, rather than creating an abstract scenario in which they imagined how they might respond.

• 36:40Speaker 01

  All of that research, in a way, really is trying to answer the question from childhood, what makes good people do bad things? And my focus has always been on trying to understand how situations shape us, mold us, and corrupt us. So, starting with an evil orientation, what I try to do is create evil. It's really studying evil from the inside out. You know, theologians, poets, dramatists, sociologists, you know, criminologists have studied evil, but they've studied evil in place. So what I try to do that's unique is create it. You see the process of transformation. You see people who start off on day one, normal, healthy, you put them in role, and then you see the divergence.

• 37:23Speaker 01

  The role, the role becomes the person. And you play a character, and then it becomes your identity.

• 37:32Shankar Vedantam?

  Over the years, Phil went on to work on other topics. For a time, he was president of the American Psychological Association. Around 2010, I remember attending a talk he gave at a psychology conference. The line of young scholars who waited to shake his hand afterwards stretched the length of a very long ballroom.

• 37:55Shankar Vedantam?

  Phil Zimbardo died in October 2024. He was 91 years old. When we come back, the larger lessons of the Stanford Prison Experiment. You're listening to Hidden Brain. I'm Shankar Vedantam.

• 38:20Shankar Vedantam?

  This is Hidden Brain. I'm Shankar Vedantam. In 2004, after the horrific abuses at Iraq's Abu Ghraib prison came to light, American leaders like President George W. Bush, Vice President Dick Cheney, Defense Secretary Donald Rumsfeld, and the Chairman of the Joint Chiefs of Staff, Richard Myers, said that the servicemen and women who had perpetrated the abuses were just bad apples. The lawyer for one of the servicemen got in touch with Phil Zimbardo.

• 38:47Speaker 01

  I became an expert witness for one of the guards, Chip Frederick, because I knew that these were good apples that somebody put in a bad barrel. That's the metaphor I started using. In fact, I think I know I gave an interview at NPR. And I was the first to say, I want to believe our American soldiers are good. They're not bad apples, as Cheney and Rumsfeld and Bush and General Myers say. I believe they were good apples when they got there, and somebody put them in a very bad barrel. And that barrel looks exactly like the prison study. So I got to know, really, everything there is to know about Abu Ghraib.

• 39:20Shankar Vedantam?

  The more Phil read about the abuses in the prison, the greater the parallels he saw with the Stanford Prison Experiment. It told him, notwithstanding all his errors and misjudgments, the study had been on to something really important.

• 39:33Speaker 01

  The only abuses happened in that prison on the night shift. None happened on the day shift. And it turns out, Abu Ghraib was part of the unit, was the center of interrogation. So you have military intelligence with its set of interrogators interrogating. Now, they're not getting any information. For the military, it's called actionable intelligence, because what happened was, when the insurgency broke out, the military was caught blind. They had no idea this was going to happen. So they started arresting all men and boys around explosions. So they had no information. But now, they're interrogating them, and they're getting nothing. So military intelligence goes to the head of military police and says, "We need your guys to help us." They got to prepare the prisons for interrogation, break them, take the gloves off, all this

• 40:18Speaker 01

  euphemism. And so, when we interrogate them, they're going to spill the beans.

• 40:23Shankar Vedantam?

  Much like in the Stanford Prison Experiment, the young guards in Abu Ghraib received the message that their prisoners needed to be humiliated and brought to heel. At Stanford, those messages implicitly came from Phil himself. In Iraq, they came from senior officers and in the name of national security and patriotism.

• 40:41Speaker 01

  And then, in three months, no senior officer ever goes down to a dungeon to see what's happening. So this gives them complete liberty to reproduce the Stanford prison study in spades, namely to do whatever you want. The guards were not part of the interrogation team. They were simply humiliating, tormenting the prisoners to break their will. So this is the clearest situational variable. They give guards total power with no oversight, recipe for abuse. And in fact, what they said was, every time an explosion goes off and one of your buddies dies, his blood is on your hands, explicitly. So it's not like these guys were getting off on a torture.

• 41:24Speaker 01

  Essentially, you are part of our national security realm. And if you remember, in the war, it was, everybody is for us or against us. So really, if you don't do this, you're suspect.

• 41:38Shankar Vedantam?

  Once the sides were clearly drawn and marked, once the stakes of doing their jobs were laid out, Phil says the situation came to shape the behavior of Chip Frederick and the other young guards.

• 41:49Speaker 01

  So the guards got sucked in. But then, as we said earlier, it's now the night shift. So the biggest contributor to evil is boredom. And so you're bored, you got 12 hours to kill, and places filled with stress and danger. And the only playthings are prisoners. And most of the prisoners are already naked. And it's never been the case we have female guards with naked prisoners. Again, for Muslims, you never show yourself naked in front of a woman. And so the sexual agenda is there. I mean, it's just boiling over. And it only goes down. It gets worse and worse and worse. So the images, the dozen images that were shown on television, are almost the least objectionable. The others are even worse.

• 42:38Shankar Vedantam?

  When I interviewed Phil in April 2013, he told me he continued to be fascinated by the idea that ordinary people could turn into monsters. He had published a book called The Lucifer Effect: Understanding How Good People Turn Evil. Sitting across from me at a studio at NPR, Phil cited the words of the historian and philosopher Hannah Arendt about the Nazi leader Adolf Eichmann.

• 43:03Speaker 01

  Hannah Arendt, in trying to understand Eichmann, this brutal killer, coined the term "the banality of evil", meaning, "this guy looks like your Uncle Charlie." I mean, her phrase is, "he was terrifyingly normal."

• 43:16Shankar Vedantam?

  Phil told me he had started to ask himself a new question. If circumstances and situations could turn people bad, couldn't different circumstances and situations turn people good?

• 43:28Speaker 01

  And I said, "Well, isn't that true? If we flip it, isn't there the banality of heroes? That most heroes are ordinary people, everyday people. They do little things each day that we never know about unless they live in a major media city and somebody has to make a videotape." Then I started thinking of heroic things that I knew people did. And then I said, "Gee, now, we should celebrate heroism more than we do." Well, the problem is with a lot of the stuff on heroes, it really made them seem extra special. These are male warriors, Agamemnon, Achilles, Samurai. And there's almost no research on heroism.

• 44:09Shankar Vedantam?

  Phil started working in high schools, helping students understand the steps that lead people to betray their values and how they could stand up to injustice.

• 44:18Speaker 01

  We started developing classroom modules, which first started off by saying, "Be aware of the power of the dark side." So we teach you about the prison study, the messages of the Milgram study. We show videos of a woman lying on a subway station in Liverpool Station in London. In five minutes, the little clock is going, 35 people pass right by, and nobody stops. The question is, "What's wrong? Are these bad people?" And so the kids say, "We would help." Well, what's the difference between you sitting here and people there? And they come up with situational differences. And then we teach them these lessons: the bison effect, prejudice, discrimination.

• 44:56Speaker 01

  We get the college kids to teach high school kids, high school kids to teach middle school kids. It offsets all the evil I've done. It's been really enriching.

• 45:14Shankar Vedantam?

  In 1492, Christopher Columbus set sail from Spain in search of the great continent of Asia. He figured he needed to go west. Some of his misjudgment was based on erroneous maps and miscalculations about the size of the Earth, and some of it was simple overconfidence. Convinced he was on the right track, Christopher Columbus sailed across the Atlantic Ocean. When he landed in the Bahamas, he believed he had found Asia. He labeled the people of the region Indians. He kept going, believing he would soon stumble on China and Japan.

• 45:50Shankar Vedantam?

  In the centuries that followed his voyage, hundreds of cartographers and historians corrected his numerous mistakes. They mapped the Americas, documenting the lives of the indigenous people who had lived there for centuries and the many harms that European visitors had done to these native groups. Where the Italian explorer was all swashbuckling derring-do, they were careful and prized accuracy. In every era, there are people like Christopher Columbus. They are the heroes and villains of our history books, the bulls in our china shops. They leap before they look. They take a grand or outlandish idea and run with it. They go out on limbs in pursuit of their ambitions.

• 46:34Shankar Vedantam?

  Sometimes, they change the world for the better. Sometimes, they're a disaster, a cautionary tale for the rest of us. Cartographers, by contrast, are careful, detail-oriented. They're the ones who pressure-test the claims of the explorers, the ones who develop the detailed maps of the new worlds the explorers have haphazardly sketched for us. Cartographers often roll their eyes at the antics of explorers.

• 47:06Shankar Vedantam?

  Phil Zimbardo was an explorer. He wanted to answer a big question and make a splash while doing it. The pull of big provocative ideas was irresistible to him, and his work continues to provoke conversations about the nature of good and evil. But in his zeal to explore these big ideas, he was also reckless. He overlooked details and cut corners in the way he constructed his most famous experiment. He wrote roughshod over the safety and concerns of the young volunteers who were ostensibly in his care. And yet, it is also true that he generated enormous public interest in psychology.

• 47:48Shankar Vedantam?

  In the late 1990s, when the internet was still in its infancy, I remember running a Google search for Stanford. I wanted to look up the university directory for an expert I needed to interview. But the first result that popped up on my screen was not for the university. It was a link to the Stanford prison experiment. Phil helped us colleagues see that questions of morality were not merely philosophical questions, but scientific questions. The field of moral psychology is an extraordinarily robust area of study today. Phil also helped the general public recognize the value of psychology in answering some of the most pressing questions of our time.

• 48:29Shankar Vedantam?

  When we see genocides and mass murder around the world today, when we see human beings dehumanize one another, many of us no longer look for religious or theological explanations. We too ask ourselves the question that a boy once asked himself at a high school in the Bronx. What is it that prompts good people to do evil things? Hidden Brain is produced by Hidden Brain Media. Our audio production team includes Annie Murphy-Paul, Kristin Wong, Laura Quarrel, Ryan Katz, Autumn Barnes, Andrew Chadwick, and Nick Woodbury. Tara Boyle is our executive producer. I'm Hidden Brain's executive editor.

• 49:15Shankar Vedantam?

  If you love our show, please help to support it. Join our podcast subscription, Hidden Brain Plus, for ideas and interviews you won't hear anywhere else. Go to either apple.co/hiddenbrain or support.hiddenbrain.org. You'll be providing us with vital support to bring you many more episodes of Hidden Brain in the future. I'm Shankar Vedantam. See you soon.

• 49:45Speaker 05

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• 50:11Speaker 02

  Shop gifts no love at Walmart.