Unchaining the Stanford Prison Experiment: Philip Zimbardo’s famous study falls under scrutiny

Nov. 13, 2018, 11:57 p.m.

On March 7, 2007, Philip Zimbardo used his last lecture at Stanford to declare that he’d left his most famous experiment behind.

Capping off a discussion of the 1971 findings that made him a public figure, movie character and textbook staple, the renowned psychology professor told the audience he was ready to start probing acts of heroism, rather than acts of abuse.

“I’m never going to study evil again,” he said.

The room was packed – not unusual for a course featuring Zimbardo, whose six-day Stanford Prison Experiment drew great attention as a dramatic demonstration of the power of roles and the way ordinary people can turn cruel under the wrong circumstances. Students who frequented the psychology department in Jordan Hall might have noticed a plaque marking the site of the study: Nearly 40 years prior, the building’s basement hosted a mock jail of college students in which – as Zimbardo tells it – student guards went so rogue with power and prisoners became so depressed that the professor had to call off his experiment. A colleague gushed later that week to Stanford News that Zimbardo’s research and teaching contributions were “probably unmatched by anyone – not only at Stanford, but throughout the world.”

Despite that switch to heroism he announced in his farewell lecture, Zimbardo remains inextricably linked to his most controversial work, conducted when he was in his 30s and newly tenured at Stanford. Now, though, Zimbardo battles accusations of questionable methodology and scientific fraud.

A journalist’s revisiting of the prison experiment has cast new doubt on its value: In an article quickly picked up around web, Ben Blum highlights participants’ claims that they were just acting and archival footage that he presents as evidence Zimbardo and his collaborators worked to elicit particular behavior. A French book by author Thibault Le Texier, published two months before Blum’s article, catalogues even more criticisms. While the summer’s discussion of the Stanford Prison Experiment focused on Blum’s arguments, an English-language summary of Le Texier’s findings – slated to publish in American Psychologist this month – could set off even greater scrutiny of the study as it reaches a U.S. audience.

The ensuing debate is rocking 85-year-old Zimbardo’s legacy in a way that decades of long-simmering but quiet critiques of the study didn’t, reshaping the experiment’s public image amid growing skepticism of influential psychology studies. Those who questioned the experiment for years are wondering why the reckoning took so long.

Others find value in the study despite its criticisms – and wonder if some of the blaring headlines sparked by Blum’s article, which asserts that “The most famous psychology study of all time was a sham” suffer from the same lack of nuance that characterized earlier coverage of the prison experiment.

Caught in the center, even Zimbardo seems torn between describing the experiment as an elaborate show and touting its scientific value. This comes across when he responds to the account of James Peterson M.S. ’91 Ph.D. ’74, a prisoner in the study who says he was let go early for no apparent reason.

Peterson, then a Ph.D. in engineering, recalls doing “a really lousy job as a guard” – nerdy and socially awkward, he drew weird looks during a count-off of the prisoners’ numbers by whimsically ordering the other students to yell out their ID numbers in “nines complement,” a computer science term.

Peterson has a hunch that his silly performance got him kicked out of the experiment. After his shift finished, he claims that someone on the research team – he doesn’t remember who – called him over to say he didn’t have to return. It turned out he wasn’t needed anymore, Peterson said.

Faced with this story, Zimbardo said he doesn’t remember Peterson but didn’t attempt to contradict Peterson’s account. Instead, he explained that “it might have been that Peterson just didn’t want to get into the role. That is, you know, just didn’t want to force the prisoners to do push-ups and jumping jacks and all the other things.”

“The only reason we would let a guard go,” he said, “is if he was not playing his role.” Zimbardo doesn’t seem to see an issue with removing someone from the experiment for failing to display the role-conforming behavior the researchers were observing for.

“The point is, it’s a drama,” he says. “You have to play the role in order for the whole thing to work.”

In 1971, Jordan Hall hosted a mock jail of college students in which — as Zimbardo tells it — student guards went rogue with power and prisoners became depressed (Courtesy of Stanford Libraries).

‘Nobody read it’

Siamak Movahedi, a professor at the University of Massachusetts Boston who specializes in social psychology, was one of the Stanford Prison Experiment’s earliest doubters. In 1975, just a few years after the study made headlines, Movahedi and his colleague Ali Banuazizi published the first major methodological critique of the experiment in American Psychologist.

The two scholars argued that the Stanford Prison Experiment did not show students genuinely consumed by their roles as prisoner and guard. Rather, they said, it showed participants engaging in a sort of theater – acting out stereotypical guard and prisoner behavior in response to what psychologists call “demand characteristics,” or cues on the goals of an experiment that participants pick up on. Movahedi and Banuazizi are skeptical of the idea that a bunch of white college students roleplaying for a week could reproduce the psychological workings of a real prison.

Their paper went largely unnoticed until just recently, when Movahedi started to notice surprising readership statistics from sites like academia.com – where, in August, the paper was downloaded at least 400 times.

“For 40 years, nobody read it,” Movahedi said.

The sudden interest raises a question for many of Zimbardo’s critics in the psychology community: What took so long? You don’t have to read Ben Blum’s article, they say, to realize that Zimbardo’s project was flawed in an experimental sense.

And yet, Movahedi’s issue is with Zimbardo’s approach, not his message about the power of the situation. Several decades ago, a San Francisco attorney called Movahedi looking for criticism of the prison experiment’s findings; Zimbardo was set to testify in a case about prison abuse, and the lawyer wanted Movahedi to speak against him. Movahedi promptly called Zimbardo and offered to write him a note of qualified support.

“I sent him a letter saying we simply have some disagreements with you on methodological issues; however, we completely share your conclusion and hypotheses that it’s the structure which leads to some of this oppressive behavior,” Movahedi recalled.

Movahedi understands why the prison study has stuck around. For one thing, it’s a hit with students. It’s a good teaching tool that gets their attention and pushes them to consider roles and social structure. Movahedi presents it in his classes every October, albeit with a discussion of its shortcomings.

He calls the prison study an “evocative object,” something useful for thinking but not for real data on a research question.

“It’s kind of a little play-acting that makes a point,” he said.

Although Zimbardo calls his study a “drama,” he views it as more than mere theater. He presents it as research from one of the top psychology departments in the country, as evidence for legal cases and debates over U.S. policy. He’s spoken before Congress. He’s called for prison reform. He testified for the defense in the Abu Ghraib guard trials, saying that situational forces just like those in the Stanford Prison Experiment led a good guy to abuse detainees.

Movahedi’s coauthor Banuazizi said he’s disappointed that Zimbardo chose to ignore the criticisms and continue pushing a “glorified” narrative of the experiment.

“In doing so, I believe, he did a disservice to his own reputation and, more importantly, to the field of social psychology,” Banuazizi said.

Philip Zimbardo played the role of both head researcher and prison warden in his infamous Stanford Prison Experiment (Courtesy of Stanford Libraries).

Zimbardo responds

Zimbardo has long acknowledged problems with his study, although he continues to defend vociferously against many of the issues raised by people like Banuazizi, Movahedi, Le Texier and Blum. “It wasn’t a formal experiment,” he told Stanford Magazine in 2011. “My colleagues probably never thought much of it.” He says he should never have played the prison warden in his own experiment and wrote early on about the way that he became overly invested in the drama as it unfolded. But he hasn’t budged on the experiment’s core validity.

The conclusions he describes from his experiment today are more qualified than what he expressed in earlier interviews. Faced with accusations of overhype, Zimbardo focuses in on the participants who took their parts to extremes: He points to late-night video that captures guards going far beyond tough talk, directing prisoners to pretend to be camels and simulate sex. He emphasizes now that students varied in their behavior and that the prison experiment showed what could happen to someone under extreme circumstances, rather than what will happen to anyone.

Back in 1971, Zimbardo told The New York Times a more sweeping story.

“It is clear that almost anyone put in a certain kind of situation can be made to behave toward other human beings in a demeaning and brutal fashion,” he said.

“In the beginning it was overstated, and probably even from me,” he said when asked about the surety of that quote. “I was too close to it.”

Critics say that Zimbardo is still in denial about the nature of his experiment, and Blum’s piece published on Medium this June presents a host of issues to answer for. One prisoner says that his much-publicized mental breakdown was actually a ploy to leave the experiment early and prepare for the GRE (he joined the study thinking he’d be able to spend the day reading). Others recall trying to quit the experiment, only to hear from Zimbardo that they couldn’t leave – a story supported by a recording, despite Zimbardo’s denials. As for Zimbardo and his fellow researchers’ claims that guards slipped organically into their roles, Blum points to audio of a researcher instructing a guard to treat prisoners more sternly. “I was given the responsibility of trying to elicit ‘tough guard’ behavior,” the researcher writes in his notes.

Zimbardo’s nearly 7,000-word response to his critics, posted on his website devoted to the Stanford Prison Experiment, dismisses the various charges against his study. He points out that he’s the one who put all his experimental materials in public archives — providing his critics with their ammunition.

“The key is, as I say in my response, nothing is hidden,” he said.

Researchers who guided guards were just trying to make sure reluctant students participated in basic tasks, Zimbardo says. A study by two British researchers – often cited as a failed attempt to replicate the Stanford Prison Experiment – differed from the prison study in key ways. Participants were filmed for broadcast on a BBC TV show, something Zimbardo argues would surely warp results. And the prisoner who now claims he faked his breakdown? His account can’t trusted, Zimbardo says, given that he told a story of a genuine mental crisis when interviewed for a documentary back in the 1990s: “The Stanford Prison Experiment was a very benign situation, but it still caused guards to become sadistic [and] prisoners to become hysterical,” he said at the time.

Archival materials paint a more complex picture of the prisoner’s exit. In raw video that was edited out of the documentary, the prisoner also states that he acted up in order to leave the experiment. Back in 1971, he told researchers that he “made up several schemes whereby [he] could get out. The easiest one … was just to act mad, or upset, so I chose that one.”

Even the prisoner said he was unsure how exactly to view his exit from the study. Act and real emotion were muddled for him, he explained.

“The big thing, I couldn’t decide whether the prison experience had really freaked me out, or whether I induced that freaked out thing,” he says in an tape labeled “Final Reactions to the Experiment.” “Even while I was being upset, I was manipulating and I was being upset.”

Zimbardo’s public response does not explicitly address all of French author Le Texier’s specific criticisms. Neither does much of the prison experiment’s recent discussion in the media; U.S. coverage of Le Texier’s work has been minimal.

“It looks like the truth is not interesting if it’s not written in English,” Le Texier wrote in an email to The Daily, adding that he sent Zimbardo an earlier version of his paper in April. He contends that Zimbardo focused on some of Blum’s points because they’re not always anchored in documents from the archives. Testimony from participants nearly 50 years later is not nearly as convincing as recordings and contemporaneous notes, Le Texier said.

The archives, for example, clarify that guards knew what outcomes the experimenters were hoping for, Le Texier writes in his paper. On orientation day, Zimbardo told his recruits that his grant was meant “to study the conditions which lead to mob behavior, violence, loss of identity, feeling of anonymity.” Le Texier also notes that some guards spoke or wrote to researchers of seeing themselves as experimental aids rather than subjects – people helping the scientists study prisoners’ reactions.

Zimbardo declined in an email to respond specifically to Le Texier’s points, referring The Daily to his lengthy public statement.

Another one of Zimbardo’s rebuttals to his detractors involves an opinion piece published in The Stanford Daily in April of 2005. In the op-ed, Carlo Prescott – an ex-convict who served as consultant on the prison experiment – slammed Zimbardo and Maverick Entertainment, the production company behind the final iteration of the Stanford Prison Experiment movie. Prescott takes credit for several of the discipline techniques used by guards in Zimbardo’s study, like covering prisoners’ heads with bags.

The problem, according to Zimbardo: Prescott never wrote the piece. Zimbardo instead pins the op-ed on Michael Lazarou, a producer who lost the rights to a movie about the prison experiment and who Zimbardo theorizes wanted to get back at him.

“It’s white boy’s language, it’s not the language of the ghetto,” Zimbardo says to explain why Prescott, who is African-American, couldn’t have written the critical article. Zimbardo’s online response puts the claim less bluntly: “The writer had a very distinctive legalistic style and vocabulary, not at all like Carlo’s,” he writes.

Zimbardo has rounded up other evidence, but the truth of the matter is unclear. Seeking a retraction of the op-ed this summer, following broader public criticism of the experiment, he offered The Daily corroboration from Brent Emery, the Stanford Prison Experiment movie’s producer. Emery provided emails from 2005 in which he says Prescott denied writing the piece. In an email this summer to The Daily’s editor-in-chief, Emery said that Prescott had also told him Lazarou drafted the op-ed for Prescott to sign. Meanwhile, in a recorded phone call posted to Zimbardo’s website this summer, Prescott affirms to the professor’s assistant that he was never involved in the article in any way. The Daily does not have access to its op-ed correspondence from 2005, and opinion editors from the time did not recall details of publishing the piece.

Several months after first raising the issue, in late September, Zimbardo presented The Daily with a typed retraction request that he said Prescott had signed. He told The Daily he drafted the letter. When asked in August about the retraction request that Zimbardo was eagerly pursuing on his behalf, Prescott said he did not want to speak and hung up on the paper’s editor-in-chief.

Contacted while The Daily was still weighing the retraction request, Prescott initially did not respond with comment for this story. Reached by phone on the morning of Oct. 19, after the retraction request was denied, Prescott refused to answer questions and said he did not want to be bothered again.

“I’m tired of being tortured by something that happened in the past,” he said.

“It didn’t pan out for me,” he said at one point, referring to the prison experiment. He repeated the sentiment later: “It didn’t work for me.”

Asked to discuss the retraction request, Prescott hung up.

Later that morning, Zimbardo sent The Daily’s reporter and editor-in-chief an email with the subject line, “DR ZIMBARDO URGES YOU TO CEASE AND DESIST FROM CALLING CARLO PRESCOTT.” Prescott, he said in capital letters, was not well and did not want to talk with student reporters about the Stanford Prison Experiment, “NOW OR EVER.”

“I SHALL BE TAKING THIS CASE TO MY LAWYER SOON,” Zimbardo closed his email.

Lazarou, for his part, denies any involvement with the op-ed and provided The Daily with an email chain from 2006. In the chain, he tells an accusatory Zimbardo that he spoke with Prescott, and that Prescott never denied authorship. In fact, he writes, Prescott recalled sending a similar letter to an LA Times reporter in response to a story on the prison experiment. (The LA Times writer declined to comment).

For Lazarou, the whole episode is an indicator of how much the summer’s events have frazzled Zimbardo.

“From his perspective, I think it’s self-preservation,” said Lazarou, who, with growing alarm, looped in his lawyers this fall after seeing Zimbardo’s accusations against him pop up in a Wikipedia article. “Unfortunately, you can’t make shit up about people.”

Over the phone, Lazarou — like Prescott — projects frustration. He said he’s baffled by ongoing discussions of the Stanford Prison Experiment, baffled that people are still asking him about movie rights he lost more than a decade ago. He’d already been contacted by Blum the freelancer, and now he was on the phone with another reporter, denying authorship of a 13-year-old, student newspaper op-ed that Zimbardo said was borne out of revenge.

“What’s going on?” he said. “Why is this continuing to – why is this still – what’s going on?”

A 2005 op-ed credited to Carlo Prescott, an ex-convict consultant on the Prison Experiment, claims that Prescott was behind certain guard behaviors like covering prisoners’ heads with bags. Zimbardo disputes the authorship of the op-ed (Courtesy of Stanford Libraries).

Changing understandings

Despite the heavy scrutiny, Zimbardo’s experiment seems unlikely to leave either the classroom or public discourse.

Chris Farina, who teaches AP Psychology at Palo Alto High School, has mixed feelings about the prison experiment, which he presents to students as a classic example of how a person’s situation can influence their behavior. After reading up thoroughly on both sides of the argument, he doesn’t think he’ll stop teaching the study – or showing his students “Quiet Rage,” a documentary that largely hews to Zimbardo’s side of the story. He’ll just spend more time discussing the experiment’s methodology, probing its weaknesses.

Farina doesn’t quite buy the summer’s headlines declaring the prison experiment a “sham.”

“They seem as overhyped as they’re claiming the Stanford Prison Experiment itself is,” he said. “Does it have some problems with it? Absolutely. But a total sham? I don’t know.”

Some researchers believe it’s time to kick Zimbardo’s prison experiment out of the psychological canon. Simine Vazire, a psychology professor at UC Davis and advocate of so-called “open science” – which emphasizes integrity and replicability in research – marvels that it took the examination of journalists to force a serious reevaluation.

“Psychology wants to be respected as a science,” she said. “And so I think it’s hard to criticize the things that have actually penetrated into the public.”

As cofounder of the Society for the Improvement of Psychological Science, Vazire has been at the front lines of what scientists dub the “replication crisis” – a realization among scientific communities, including the psychology community, that many famous findings are not reproducible. With attempts at replication felling more research, the open science agenda isn’t always popular. Vazire said she understands why influential scientists and gatekeepers in her field push back.

She wishes, though, that this pushback took place more frequently in the open.

“Instead what I see happening a lot is people in meeting rooms making decisions, and sometimes I’m in that room with them, and the arguments I hear are not really scientific arguments,” Vazire said. “They’re more about the politics or whose toes are going to get stepped on, and I think those arguments wouldn’t stand up if they were made publicly.”

Popular psychology textbook authors surveyed by The Daily said they are tweaking, rather than cutting, their coverage of the controversial study. The few scientists who keep the study out of their texts said they never included it to begin with. “The study is so obviously methodologically flawed as to be worthless from a scientific perspective,” said one author, Boston College psychology professor Peter Gray.

Several authors felt unable to leave the prison study out, given its cultural cachet. John Mitterer, whose “Introduction to Psychology” textbook already devotes half its discussion of the prison study to criticism, puts the dilemma this way: Should we leave Freud out because his theories have been debunked? What about Jung? “These are all things that are already part of the popular imagination,” he said.

Mary Hughes Stone, a professor at San Francisco State, also won’t stop teaching the prison experiment any time soon. While she believes the study provides valuable insight into human behavior, she said she asks students to think critically and never presents any finding as definitive.

But nuances are often lost in introductory courses, and a student video project on the prison experiment passed on by Stone displays little awareness of the complexities that all sorts of critics, from Banuazizi to Blum, have catalogued. The student sums things up neatly in voiceover as the screen fades to black: “[Zimbardo’s] experiment proved that any person can turn bad under certain pressures and roles.”

The Stanford psychology department has not issued a statement on the summer’s controversy over the Stanford Prison Experiment (RYAN COHEN/The Stanford Daily).

Silence at Stanford

Over the summer, as scholars weighed in on Twitter and in the media, one group of psychologists was particularly quiet about the Stanford Prison Experiment: Zimbardo’s colleagues at Stanford. Few have joined the conversation publicly, and the department has no official comment, following guidance from University Communications.

Brian Wandell, a former psychology chair, believes Stanford has “a special responsibility” for ensuring that the experiment it gave its name to is correctly understood. He demurred, though, when asked whether Stanford is doing a good job of this – “no judgments from me,” he says. It’s the same answer he gives when asked whether Zimbardo has been forthright about his study.

“I don’t want to judge people,” he responds. He likens the study to a work of art, something lacking qualities of a true experiment but still instructive. He saw Zimbardo’s response to the criticisms – emailed out to all the Stanford psychology faculty – but he says he’d need to go back and spend more time on it to weigh in.

“We know there’s no control group,” Wandell added later. “It’s an event. It’s a demonstration. And Phil in his own self-description always said about himself that [was] what he was good at – he was good at demonstrations.”

Wandell is far from Zimbardo’s area of expertise, social psychology. He spends his days thinking about magnetic resonance imaging and how pictures form on the back of the eye. And so, early in the summer when Blum’s article came out, Wandell turned to his colleagues in social psychology. What did those closest to Zimbardo’s work think?

Wandell says he never got much of an answer. One professor agreed to circle back with him later, when they got a chance to talk in person, but the conversation hasn’t happened yet. Another faculty member was reluctant to dig into the issue.

“He just felt it’s a sad end to Phil’s career,” Wandell said. “So we didn’t go over it.”

Lee Ross, one of only two Stanford professors in Zimbardo’s subfield who agreed to speak with The Daily, has been more vocal on behalf of his longtime colleague. He is one of the few remaining psychology faculty who were present in 1971 when Zimbardo ran his study. Amid all the controversy this summer, he emailed his thoughts out to the entire department, responding to a request from Zimbardo to help him fend off allegations of fraud.

In his note, Ross critiqued the experiment only gently, making a case for its illustrative value. “It showed what could happen and made us all think about exactly why it unfolded as it did,” he wrote. He stresses that the study was an “N=1” demonstration, just one of many possible outcomes influenced by the personalities that Zimbardo and his team happened to recruit.

Ross questions the study’s application to a standard U.S. prison, where employees’ roles are more circumscribed than those of Zimbardo’s guards. Ross believes his colleague’s work applies most fruitfully to situations like Abu Ghraib, where guards were able to use -–and abuse – greater discretion.

“[The study] captured the extent to which people put in positions of authority without clear rules tend to improvise and look to see what they can get away with, does anyone stop them,” Ross said.

When Blum’s article came out, Ross said, Gordon Bower – the other Stanford professor who briefly glimpsed the prison experiment firsthand – wrote to him. ‘Should we do something?’ They wondered. Should the department publish a defense? (Bower says he does not recall this conversation). Eventually, Ross said, they agreed that a coordinated Stanford statement would be inappropriate: “Some of us know the situation well and some don’t; we should be free as individuals to say whatever we want to.” Bower wrote a public testimonial to his friend’s character; Ross emphasizes that his colleague is a “serious scientist” with many important textbook and research credits. The department, though, stayed silent.


The showman

One word comes up repeatedly when people describe Zimbardo: “Showman.”

His fame is entwined with his ability to captivate public attention with his work, setting his sights on not only journals but also TED Talks, late night shows and Congressional hearings. For many admirers, this showmanship is a strength that helped Zimbardo fill classrooms and draw students to his field: Zimbardo taught his courses with the same theatrical flair that characterized his prison study, from the hypnosis demonstrations to the blaring music that opened each class and that Zimbardo selected to match his subject matter. A lecture on memory might begin with Barbra Streisand’s “The Way We Were,” a class on the prison experiment with Santana’s “Evil Ways.”

The academic world can be suspicious of those who cater readily to a general audience. One former Ph.D. said that in a way, Zimbardo was ahead of his time – a zealous communicator who sought out wide impact long before the likes of Malcolm Gladwell led more academics to embrace popular science.

But Susan Brennan Ph.D. ’90, now a psychology professor at Stony Brook University, suggests Zimbardo’s ambitions were not so out of step with those of the department. Yes, Zimbardo was a showman, “But we were being trained to be a certain kind of impactful scientist,” she said.

As a graduate student at Stanford in the late ‘80s, Brennan recalls being coached by other faculty in the art of presentation to a general audience. “They would say, ‘Well this is all well and good, but it’s just not very interesting, you need to be upfront about the interesting part,’” she said. “‘You don’t need to present all the details.’”

“That’s true in a good talk,” Brennan said, but in a research report it’s crucial to share the nitty-gritty elements that allow others to reproduce your work.

“I’ve since come to believe that it’s super, super important to be careful about the message you convey,” she said. She thinks her field’s mindset is shifting similarly amid hand-wringing over failed replications, although she’s bothered by certain trends, like popular journals’ publication of quick-read articles with “gee-whiz findings” but few details. “I don’t like it, in general, when the need to be a showman outweighs the need to be accurate and precise and to craft a message appropriately.”

Zimbardo’s CV is lengthy, his publications in the hundreds, his research spanning everything from shyness to how our concepts of time influence our thoughts and behavior. Much of his work, Brennan says, is respected and well-replicated.

However, having studied experimental design and the way that even an experimenter’s gender can alter the way subjects behave, she has little confidence in the prison study’s results after reading this summer about details that never made it into the standard story.

“If you tell an undergrad what you’re expecting, even if you signal it without telling them, most of them will try to give you what you want,” she said.

Brennan’s most vivid memory of Zimbardo, from back when she worked as his teaching assistant, involves butting heads with the professor when she felt that his efforts to entertain during a lecture became inappropriate. Older than most of her peers and emboldened by her pre-Ph.D. years working in tech, Brennan said, she emailed Zimbardo to suggest changing some images on presentation slides that she thought could come across as sexist.

She says she remembers one slide in particular, of a blonde woman posed provocatively on Stanford’s campus, that struck her as problematic – it was meant to jokingly illustrate why Zimbardo came west to the University. By Brennan’s account, Zimbardo replied to her email on editing the slides along the lines of, “not necessary.”

Zimbardo denies responding that way and said that, on the contrary, he used the slide as launchpad for discussion before cutting it. By his account, he mentioned the issue during his next class, asking for a show of hands to indicate who found the slide offensive and inquiring why no one else had challenged him to remove it. “I would have been impressed if he had [done that],” Brennan said – she says the discussion ended with Zimbardo’s email.

As a teacher, Zimbardo recounted, he regularly encouraged students to speak against him and spent 10 minutes of class time each week on an “open microphone” session in which class members could criticize anything he’d said.

“That’s something I did which was unique,” he said.

Zimbardo takes issue with the “showman” descriptor and its potentially critical implications. Holding a large lecture class’s attention and making students care about your material is hard, he said. There’s nothing wrong with being an entertainer.

Several former Ph.D.s felt the same way, praising Zimbardo’s compelling presence in the classroom. He was a beloved teacher to many: Emailing the professor after this year’s homecoming weekend, one alum recounted that, when asked to sum up their Stanford experience in a word, some people volunteered the name “Zimbardo.”

“His undergraduate introductory psychology classes were so popular that at one time there was some discussion about whether they could be held in the football stadium,” wrote Craig Anderson M.A. ’78 Ph.D. ’80, now a psychology professor at Iowa State University, in an email to The Daily. “Stanford University has benefited greatly from having him on the faculty.”

And Zimbardo is open about his desire to rivet audiences.

“I’m always thinking of, how can I frame it, how can I say it so my mother would say, ‘you know what, that’s interesting,’” he said in the Stanford News video marking his farewell lecture in 2007. “It’s important to get it right. But to me, it’s equally important to make it interesting. And in academia there’s not as much value on making things interesting.”

“There’s not the world of academia and the general public,” he added. “It’s people. People with different levels of education, people with different levels of interest, and I want to reach the world.”

Psychology, and in particular social psychology, offers research findings with broad appeal and applicability to everyday lives: It tell us that we can achieve our goals with a “growth mindset,” that children mimic violence they see on TV, or that we view rudeness as a sign of power. But Wandell, the former psychology chair, thinks the desire for great impact is a common denominator at Stanford. “We like to think of ourselves more than most universities do as a university that thinks hard on topics that matter,” he said.

“When we fail, we can fail pretty big,” Wandell added. “And when we succeed, we succeed big.”

Zimbardo and his fellow researchers turned Jordan Hall, Stanford’s psychology building, into a mock jail for their experiment (Courtesy of Stanford Libraries).

Disputed lessons

For the students who responded to an ad for study participants back in 1971, the longevity of talk around the Stanford Prison Experiment is bewildering.

Some participants in the study feel vindicated by Blum, Le Texier and others’ findings. Others are confused at why, half a century later, they’re still talking about something that seemed at first like just another odd summer job.

What memories they still have of the experiment offer something for all sides.

Jim Rowney, an incoming freshman at UC Berkeley at the time of the experiment, signed up to earn $15 a day without any notion that he would participate in something important. He was saving up for a stereo for his room and thought little of the experiment after it ended. He was incredulous when, nearly 30 years later, he got a call from ‘‘60 Minutes.’’

The incredulity grew when the ‘‘60 Minutes’’ reporter began speaking of violence and drawing parallels to Nazi Germany – Rowney remembered the prison experiment as “a crappy way to make 60 bucks.”

By his fifth day in Jordan Hall’s mock prison, Rowney was filthy. His whole stay at the Stanford Prison, he never showered, and the books he’d brought to entertain himself were confiscated. Finally, he wanted out. After asking to meet with someone in charge – he can’t remember whom – he began to cry.

Two other prisoners had left early by then, after succumbing to what Zimbardo and his fellow researchers described as breakdowns induced by the stress of their role.

Rowney doesn’t remember whether he thought the other prisoners’ breakdowns were “real” or not. Regardless, he’s skeptical that his or the other students’ meltdowns show something novel about social roles’ ability to transform healthy students.

“It was more the fact that your privileges and movements and everything else we take for granted was restricted,” he said. “It was very uncomfortable. The beds were uncomfortable. The pillows were uncomfortable. Everything was uncomfortable … It was not quite what [prisoners] expected.”
Who wouldn’t have been upset? he argues.

And yet, Rowney remembers moments when he really did fall into his prisoner role, trying to impress guards with his good behavior. The climax was his “parole hearing” on the fourth day of the experiment. He didn’t even know what would happen if the parole board ruled in his favor; he just found himself appealing with all his might.

“When they started asking questions I slipped right into the role of, ‘Hey, I’m trying to be a good prisoner, can I get out,’” he said.

Several guards in the Stanford Prison Experiment have been critical of the study and its findings. One claims he was just acting; Zimbardo says his behavior went “beyond” that (Courtesy of Stanford Libraries).

Dave Eshleman, notorious as the harshest of the guards, is unequivocal that his behavior – key to Zimbardo’s narrative – was a charade. As he told Blum and has long said in interviews, he loved acting and was studying the discipline at the time of the experiment. He says he wanted to give the researchers something interesting to work with; speaking to The Daily, he added that he figured they were spending a lot of money on the study and didn’t want it to go waste. He thinks he might have felt a desire to do “a good job for the boss.”

“Every single day I went in there with the goal of, you know, making it an uncomfortable environment for the prisoners so the researchers would get the results they wanted to get,” he said.

Eshleman doesn’t recall the sort of explicit cues that Blum and Le Texier cite archives for. All he remembers now is that no one stopped him as he pushed into meaner territory. Every day, he said, he would take his act a bit further – and no member of the research team stepped in to say, “tone it down.” “So we took that as approval and support,” Eshleman said.

Eshleman’s claim of acting is swept aside in the 60 Minutes piece. “You’re trying to tell me that wasn’t a natural thing?” the reporter, Lesley Stahl, asks him, her voice skeptical. Interviewing Zimbardo later, she asks him what he makes of Eshleman.

“My sense is that’s a level of sadism that goes above an acting role,” Zimbardo says. “The belligerence, the having them to do pushups, the sit-ups, cleaning toilet bowls, it goes beyond the constraints of the role.”

Zimbardo’s response today is similar, and he points in particular to Eshleman’s sexual degradation of the prisoners at the climax of the study, right before it was called off. Eshleman, who called this moment the guards’ “ultimate escalation” after “several days of dreaming up news tactics,” said he and his friends drew inspiration from films and fraternity hazing; again, he claims it was all to help the researchers. “With that mindset, you might imagine why few considered whether their actions were ethical,” he wrote in an email.

For Zimbardo, the prisoners’ humiliation is evidence that Eshleman’s role has warped his behavior.
Critics, on the other hand, wonder if Zimbardo’s got the interpretation wrong – if what he created was something akin to the equally notorious Milgram experiment, in which experimenters pushed participants to deliver electric shocks to anonymous others. Aggressive guards in the Stanford Prison Experiment went to troubling lengths to please the people in charge, they say.

Experimental archives show that participants viewed their behavior in the study in different ways. One guard responded to a 1973 follow-up survey on the prison experiment by dismissing his actions as “contrived,” while another wrote that the worst part of his experience was the “times when [he] really felt the guard role [he] was playing.”

These days, Eshleman is often asked to speak as a guest in classes. His latest visit was to West Valley College, where his friend is a professor. When the professor announced Eshleman’s visit to her students, they reacted with horror – they thought they were about to meet a psychopath.
“They said, ‘oh my god, he’s a monster,’” Eshleman says. He laughs. “She had to tell them, look I know the guy. He’s very mild, but he’s an actor.”

And yet, Eshleman admits, there’s a certain point at which, as Zimbardo argues, the question of acting or not acting is moot. Psychology professor Ross also contends that, while participants “played their roles as best they could,” it makes little difference to a prisoner — research subject or real — whether a guard embraces the role he is hired for or enacts expectations of it.

A Los Angeles Times article from 2004 quotes Doug Korpi, the prisoner who says he faked his breakdown: “When you see it in their eyes, it doesn’t matter if they say they were just acting,” said Korpi. “They were into it.”


In March, months before Le Texier’s book and Blum’s article were published, participants in the Stanford Prison Experiment got a curious email in their inbox.

Titled “Invitation to Participate in Survey about Stanford Prison Study,” the email – sent under Zimbardo’s name – asked the former guards and prisoners to spend 45 to 60 minutes answering detailed questions about themselves and the experiment, nearly 50 years later. Stanford Psychology Professor Geoffrey Cohen Ph.D. ’98 and his lab created the survey over several years, in consultation with Zimbardo; Cohen says he wanted to reach out to participants in classic studies to probe the lasting influence of certain experiences.

John Mark ’73 knew right away that he wasn’t going to respond. He said he didn’t want to give Zimbardo anything that he could edit, that the researcher could cut and paste to serve his needs.

“I don’t trust him,” Mark said. “I look at what he did with the experiment. And I think you can edit a lot of things to look completely differently. I don’t even give him the satisfaction of sending him back something telling him I think he’s full of shit … I don’t respond.”

He isn’t the only person to withhold. Cohen said he has yet to examine the study’s results but lamented that just six or seven of some 20 participants replied.

Mark thinks the story of the Stanford Prison Experiment will, in the end, be about the psychology of the researcher rather than the psychology of his subjects. “In the long run, it’s gonna say more about Zimbardo … than what he wrote about before he was questioned,” Mark said.

Mark signed up for the Stanford Prison Experiment believing he would be part of something noteworthy, after a close scare in which he was almost arrested in a foreign country left him particularly sensitive to the plight of prisoners. His sympathies for the underdog made him a dismal guard, called out by name in researchers’ notes for his reluctant performance.

Mark is the guard in the archival recording of a researcher urging a participant to be tougher; he has no memory of the exchange, but he recognizes his voice in the audio.

By the end of the experiment, Mark said, he felt used, angry about the conditions inflicted on participants and the way prisoners and guards were pitted against each other. The longer Mark mulls over those six days from 1971, he can’t help but feel that Stanford, a place he loves, let Zimbardo get away with questionable work. “I think Stanford was Zimbardo’s enabler,” he says. If Wandell believes Stanford has a special responsibility to make sure the Stanford Prison Experiment is properly understood, then Mark believes Stanford’s already been negligent.

Study participants who spoke with The Daily blame the media, too. They said journalists have been as eager as Zimbardo to tell a captivating story, editing irregularities in people’s accounts out of pieces or dogging them for the answers they expect to hear. Eshleman, the guard, recalls telling an interviewer at one point, “You’re asking all the wrong questions.” Rowney, similarly, remembers feeling like 60 Minutes went after Eshleman, drawing out the sinister in his responses.

“I mean, they really made him look bad,” Rowney said.

Even when participants are quoted, their views can be downplayed – as in one 2015 New York Post article that rounded up many critical voices.The reporter spoke to Eshleman as well as a highly skeptical scholar; in her research, she also came across Mark’s disavowals and the Stanford Daily op-ed attributed to Prescott.

All these people are heard out in the body of the piece. But the headline still reads, “Inside the twisted experiment that turned students into evil sadists.”


Amid the criticism this summer, Zimbardo has continued to make public appearances and promote his work. He’s pivoted from studying evil to studying heroism (Courtesy of Wikimedia Commons).

‘Food fights’

While some participants say the prison experiment has eroded their trust in Zimbardo and the media, Laura Freberg – a psychology professor at California Polytechnic State University and the president of the Western Psychological Association (WPA) – worries about how to acknowledge her field’s “food fights” without eroding students’ trust in psychology as a discipline. She believes these scientific disputes are healthy, a sign that things are working properly. Psychologists are “crabby bunch of people,” she says, and if you can find a room where everyone agrees, something is probably wrong.

But how do you do justice to a finding with many asterisks in the public sphere? Or in an introductory psych class?

“You are walking a tightrope,” she said. “You want people to think that we know what we’re doing. So if we present a conclusion in class, you want the students to have some faith … But at the same time you want to encourage critical thinking and skepticism.”

Freberg is up-front that she’s fond of Zimbardo, having interacted with him in the context of the WPA. Zimbardo’s wife, a respected psychologist at UC Berkeley, will take over as the organization’s head next year. Freberg admires Zimbardo’s career and, in particular, his recent work on cultivating people’s capacity for heroism, his pivot from evil to good.

A researcher with “a lot of respect for the classic studies” who once sparred with her textbook coauthor over whether to include the prison experiment, Freberg says she’s enjoyed watching Zimbardo and his critics parry, although she worries that he’s taken the jabs too personally and that detractors can pile on to the point of viciousness. She wonders if the contentiousness of discussion around the replication crisis might scare younger researchers, who see older professors taking highly personal hits for their work.

“You made a mistake in your interpretation or whatever, so that means you’re not a worthy psychologist anymore – that’s really destructive, and I don’t want that message going out there to younger scholars,” she said. “That’s very stifling, I think.”

In a show of unity, two researchers that have been at odds with Zimbardo for years – the professors behind the BBC prison study with contradictory findings – recently signed a joint statement with Zimbardo and his fellow researcher on the prison experiment, Craig Haney. The statement affirms scientific common ground and backs off personal criticisms, despite Le Texier and Blum’s suggestions that Zimbardo misled the public about key parts of his study.

“We regret instances in which our statements appeared to involve ad hominem criticisms or used intemperate language,” the four researchers state. “Although it is legitimate to debate the accuracy, comprehensiveness, and meaning of research reports, we have no definitive evidence that any signatory of this statement committed scientific fraud or deliberately misled others about their research findings.”

UC Davis’s Vazire, on the other hand, thinks it’s fair to criticize the scientist as well as the finding when it seems the scientist has been negligent. If a researcher is sloppy, she said, “We do have, I think, a lot of discomfort in calling that out.” She thinks critics can stay respectful without pulling punches.

“Some people think you shouldn’t even use their name, you should just refer to it as the Stanford Prison Experiment or whatever – the study without naming the researcher,” she said. “But nobody thinks that when we’re saying positive things about the study.”

“I think there’s this asymmetry that researchers want all the fame and glory and credit that comes with positive attention to their work,” she continued. “But if it’s criticism, even valid criticism, then all of a sudden it’s really important that we keep it completely impersonal.”

Within her specialty, neuroscience, Freberg has witnessed many once-accepted studies be undermined by new advances in MRI technology. The traditionally exorbitant cost of such tools meant that many early experiments built conclusions off of tiny samples of 10 or 15 people – a statistical headache. She’s watched some scientists take blows to their work gracefully: Take, for example, a professor at UCLA whose studies on social exclusion weren’t replicated. The professor had found that a dinner or party snub lights up the same brain circuit that’s activated by the physical pain of, say, whacking your shin.

“That’s a great story, I love that story,” Freberg says. She used to feature it in her textbook. But the research doesn’t hold up. The UCLA professor had to acknowledge the study’s faults, and move on.

Freberg has also watched scientists under fire dig in their heels. “It’s very difficult for people to accept the idea that maybe they don’t have as strong a case,” she says.

“Science,” she remarks later, “is a very human process.”

Zimbardo remains invested in his seminal study’s preservation in academia and popular culture, even as he expresses frustration with people’s fixation on one part of his long career. He said that those he consulted about his official response to prison experiment critics had to continually advise him to tone it down, to meet his doubters in the middle.

But the way Freberg talks, you’d think the Stanford Prison Experiment controversy was just a blip, something Zimbardo can set aside. He hasn’t shied away from public appearances following the furor over his early work. His alumni weekend lecture in October drew 300 audience members, and his Twitter account promotes recent and upcoming visits to everywhere from Abu Dhabi to Sigmund Freud University in Vienna. The former American Psychological Association head is a star at conventions and talks, sitting for hours to give autographs.

He’s slated to speak at the WPA’s annual conference in April.

“Come on down to Pasadena,” Freberg says. “We’re gonna have a good time, and you can get a selfie with Phil Zimbardo.”


Contact Hannah Knowles at hknowles ‘at’ stanford.edu.


This article has been updated with additional comments from Lee Ross. The piece has also been updated to attribute the idea that Michael Lazarou wrote an op-ed for Carlo Prescott to sign to a phone conversation with Prescott described by Brent Emery.

Hannah Knowles is senior staff writer from San Jose who served as Volume 253 Editor-in-Chief. Prior to that, she managed The Daily's news section.

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