Philip G. Zimbardo, a towering figure in social psychology who explored how good people turn evil in the infamous Stanford Prison Experiment, which devolved into chaos after college students acting as guards started abusing other students acting as prisoners, died on Oct. 14 at his home in San Francisco. He was 91.
The death was announced by Stanford University, where Dr. Zimbardo was a professor of psychology for 35 years.
Called the “emperor of the edge” by Psychology Today magazine, Dr. Zimbardo was a clever, flamboyant and always nattily dressed academician whose provocative research interests (power, evil, heroism) made him a popular figure on the Stanford campus.
In 1971, seeking a novel way to study how situations can transform behavior, Dr. Zimbardo set up a prison in the basement of Stanford’s psychology building.
He turned rooms into cells. He made a tiny closet into “the hole” — solitary confinement. And he placed an advertisement in a local newspaper: “Male college students needed for psychological study of prison life. $15 per day for 1-2 weeks.”
Dr. Zimbardo viewed his experiment as a bookend to one that had been performed in the early 1960s by the social psychologist Stanley Milgram, who had been his high school classmate and friend in the Bronx. (Asked once what the odds were that they would have gone to high school together, Dr. Zimbardo replied, “Pretty slim, I’d say.”)
In Dr. Milgram’s experiment, participants were divided into two groups, teachers and learners, in separate rooms. When learners answered a question incorrectly, an authority figure — the experimenter — instructed the teachers to administer what they thought were electric shocks. The teachers continued shocking students (or so they thought) even as they heard fake screams in the other room.
“Whereas Milgram’s research was all about the power of individual authority over an individual person, the Stanford Prison Experiment was all about the ability for a system to repeatedly create situations that strongly influence behavior,” Dr. Zimbardo said in a 2009 interview published in Teaching of Psychology, an academic journal.
For his study, he asked local police officers to arrest the students who had been hired (for $15 a day) to be prisoners. He outfitted the students hired to be guards with crisp uniforms and made them wear sunglasses to appear more inscrutable, an idea he got from the 1967 prison movie “Cool Hand Luke.”
As prisoners arrived, they were stripped, searched and deloused, a process overseen by Dr. Zimbardo, who played the role of prison superintendent. Initially there were a few giggles among the participants, but as the guards began enforcing rules, the mock prison began to feel very real.
Though critics have accused Dr. Zimbardo of coaching the guards to act sadistic, he told the guards only to “create feelings of boredom, frustration, fear and a ‘sense of powerlessness,’” according to a defense of the study on his website. They were, he said, given no “formal or detailed instructions about how to be an effective guard.”
Within a day, the guards had become abusive and were engaging in psychological torture: making the prisoners defecate in buckets, waking them up repeatedly through the night, forcing them to simulate sodomy. Several prisoners suffered emotional breakdowns. But Dr. Zimbardo kept the study going.
On the sixth day, he told Christina Maslach, a graduate student whom he would marry that year, that he was impressed by how much interesting behavior the study had revealed in just under a week.
Interviewed for the documentary “Quiet Rage: The Stanford Prison Experiment” (2004), Dr. Zimbardo said she replied, “I think what you are doing to those boys is horrible.”
“She was right,” he added. “I had to end the experiment, because that’s what it was — an experiment, not a prison. These were real boys who were suffering, and that fact had escaped me.”
Interviewed for the same documentary, one of the mock guards said, “What made the experience most depressing for me was the fact we were continually called upon to act in a way that just was contrary to what I really feel inside.”
Another mock guard said, “I had really thought that I wasn’t capable of this kind of behavior,” but that during the experiment “I didn’t feel any regret.”
The Stanford Prison Experiment has been a staple of psychology textbooks for decades, in large part because of the ethical questions it raised about studies on human subjects. It was also the subject of a 2015 movie, starring Billy Crudup as Dr. Zimbardo. (Dr. Milgram’s electric-shock study was similarly infamous.)
Discussions about the experiment resurfaced in 2004 after U.S. soldiers were accused of torturing and humiliating prisoners at Abu Ghraib prison in Iraq. Photos of the abuse were published by news organizations, including The New York Times.
Dr. Zimbardo was an expert witness in the defense of Staff Sgt. Ivan Frederick II, who pleaded guilty in military court to eight counts of abusing prisoners. The professor viewed the soldier as a victim of circumstance, arguing that psychiatric evaluations had not shown him to have any sadistic tendencies.
“The prosecutor and judge refused to consider any idea that situational forces could influence individual behavior,” Dr. Zimbardo wrote in “The Lucifer Effect: Understanding How Good People Turn Evil” (2007). “Theirs was the standard individualism conception that is shared by most people in our culture. It is the idea that the fault was entirely ‘dispositional,’ the consequence of Sergeant Chip Frederick’s freely chosen rational decision to engage in evil.”
Philip George Zimbardo was born on March 23, 1933, in the Bronx to George and Margaret (Basicia) Zimbardo. His father was a barber but was frequently unemployed. The family subsisted on government aid programs.
“I realized the only way out of poverty was through education,” he said in an interview for the Stanford Faculty Oral History Project. “I realized that very, very young. I loved school. School was orderly, it was clean, neat; there was no chaos. Poverty was left behind.”
It was at James Monroe High School that he became friends with Stanley Milgram.
During his junior year, Phil moved with his family to California. He went from being a popular student to being picked on at his new school, North Hollywood High.
But after moving back to the Bronx for his senior year, he became popular again. (Stanley wrote quips next to the student portraits in the yearbook, and for Phil he wrote: “Phil Zimbardo’s our vice president, tall and thin. With his blue eyes, all the girls he’ll win.”)
Phil marveled to Stanley about his flip-flopping social status — a prophetic conversation about social psychology, as it turned out.
“Did I change from being a nebbish to being so popular, or did the situation change?” Phil asked Stanley, according to the Stanford oral history.
They concluded that it was the situation, not his personality.
Reflecting on his career decades later, Dr. Zimbardo said, “It started with sitting around trying to figure out why I was shunned at North Hollywood High School.”
Dr. Zimbardo graduated from Brooklyn College in 1954 with degrees in psychology, sociology and anthropology. He received a doctorate in psychology from Yale University in 1959 and taught at Columbia and New York University before joining Stanford in 1968.
He is survived by his wife; their daughters, Zara and Tanya; a son, Adam, from his first marriage, to Rose Abelnour; and four grandchildren.
In addition to his study of evil, Dr. Zimbardo published widely on a variety of subjects, including shyness, the perception of time and heroism.
“The prison study will be my legacy,” he said in a 2012 interview with History of Psychology, an academic journal. “It’s going to be what is on my gravestone.”
A few weeks after ending the experiment, Dr. Zimbardo said, he discussed it in a talk to the annual conference of the American Psychological Association.
Dr. Milgram was in the audience, and he hugged his old friend afterward.
“Oh, thanks,” Dr. Milgram told him, as Dr. Zimbardo recalled. “Now you’re going to take all the ethical attacks off my shoulders, because what you did was worse than what I did in my studies.”
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