On Aug. 17, 1971, the otherwise placid community of Palo Alto, Calif. — historically one of the wealthiest enclaves in America — was awoken by the blare of police sirens. The cops were conducting a sweep, arresting 10 young men in quick succession. All were charged with felonies, and all were made spectacles of: forced to brace themselves against police cars in the middle of the street, then handcuffed and driven away.

The Stanford Prison Experiment had begun.

Even today, the SPE remains one of the most famous studies in social psychology ever conducted, and it’s the subject of a new film, “The Stanford Prison Experiment,” starring Billy Crudup as Philip Zimbardo, the experiment’s mastermind.

Professor Philip ZimbardoPhoto: Corbis

Zimbardo was then a young psychology professor at Stanford University. Weeks prior, he’d placed an ad in newspapers looking for volunteers. “Male college students needed for psychological study of prison life,” it read. “Fifteen dollars per day for 1-2 weeks beginning Aug. 14.” (That would be about $90 today.)

The ad drew over 75 volunteers, who were all given psychological testing. Zimbardo was interested only in young men who were physically and emotionally stable, with a healthy respect for the rule of law. He was out to answer one of the basest questions about human nature: Are we inherently good or evil? Does everyone, no matter how rich, educated or privileged, harbor a boundless capacity for sadism? If so, can the uneven power structure of a given institution awaken a monster?

Zimbardo knew that this experiment could be a career-maker. For the first time, Americans were watching the horrors of war on the nightly news, dispatches from Vietnam timed to dinner. In March of that year, four members of the Manson family, including Charles Manson himself, had been sentenced to death. And the world was still reeling from the horrors of World War II, the images of concentration camps, the subsequent Nuremberg trials — which gave rise to that infamous Nazi defense: “just following orders.”

Prisoners and guards

The SPE would randomly divide its volunteers into two groups, who would be monitored on camera at all times. There were 10 prisoners and 11 guards. Zimbardo himself was the superintendant, and he got into character, wearing dark sunglasses and a dark suit and tie. He warned the guards not to physically assault the prisoners, but otherwise to use any tactics they wanted.

On that first day, the prisoners were brought to the “prison,” which was located in the basement of Stanford’s psychology department. There were no windows, no way of knowing whether it was day or night. The prisoners were strip-searched and made to stand naked for a time in the yard, which was really just a hallway.

They were forced to wear loose sacks (which Zimbardo called “dresses”) and no underwear, which made them move slowly and cautiously. Women’s nylon stockings were tugged over their hair, both to mimic shaved heads and to further emasculate them. They were told they were nameless and to respond only to their prison number. The warden — Zimbardo’s colleague — read out more rules.

“One: Prisoners must remain silent during rest periods, after lights are out, during meals and whenever they are outside the prison yard. Two: Prisoners must eat at mealtimes and only at mealtimes . . . Eight: Prisoners must address the guards as ‘Mr. Correctional Officer’ . . . Sixteen: Failure to obey any of the above rules may result in punishment.”

The guards, meanwhile, had been given uniforms, billy clubs and mirrored sunglasses. They worked eight-hour shifts and, unlike the volunteer prisoners, got to go home.

Their authority was absolute: If a prisoner wanted to speak, smoke, urinate or defecate, he’d have to ask permission, and if that permission was denied, the prisoner would have to use a bucket in their cell, which would be left in the windowless room all night. Anyone who disobeyed orders would find themselves in solitary, which, for the purposes of social realism, was called “the hole.”

Despite such harsh conditions, Day One was uneventful. But just 24 hours later, there was a full-on prisoner revolt: They took off their stockings and used their mattresses to barricade themselves from the three guards on duty; those guards called in off-duty volunteer guards, then unleashed fire extinguishers on the inmates.

The guards had come up with new punishments and humiliations, and made at least one prisoner clean a toilet bowl with his bare hands.

‘Prison of fear’

A screen grab of “The Stanford Prison Experiment.’Photo: IFC

On Day Three, inmate #8612 suffered a physical and emotional breakdown, and he was released. “We did so reluctantly because we believed he was trying to ‘con’ us,” Zimbardo wrote in a 1973 story for the New York Times Magazine. “It was unimaginable that a volunteer prisoner in a mock prison could legitimately be suffering and disturbed to that extent.”

The guards were back on their heels by Day Four: A rumor was circulating that the newly sprung inmate was planning another revolt, this time bringing in help from the outside. The entire prison was quickly moved to another floor of the psychology department, and another inmate suffered a breakdown. He too, was released, as would two more over the next two days.

“In a fifth case,” Zimbardo wrote, “a prisoner was released after developing a psychosomatic rash over his entire body (triggered by a rejection of his parole appeal by the mock parole board.)”

For Zimbardo, the experiment was a raging success: Events were unfolding just as he’d predicted. But Day Six brought a most unexpected event: the arrival of Zimbardo’s girlfriend, Christina Maslach, who’d just completed her doctorate at Stanford.

“I met one guard who seemed nice and sweet and charming,” she told Stanford Magazine in 2011. “And then I saw him in the yard later and I thought, ‘Oh my God, what happened here?’ . . . I was getting sick to my stomach, physically ill.”

She told Zimbardo that what he was doing was morally wrong, and he needed to stop. Zimbardo, perhaps realizing that he was too enmeshed in his own experiment, called it to a halt.
After just six days, the SPE was over.

In that 1973 Times piece, however, he maintained that the experiment shed new and valuable light on the darkest parts of human nature.

“To what extent do we allow ourselves to become imprisoned by docilely accepting the roles others assign us or, indeed, choose to remain prisoners because being passive and dependent frees us from the need to act and be responsible for our actions?” he wrote. “The prison of fear constructed in the delusions of the paranoid is no less confining or less real than the cell that every shy person erects to limit his own freedom in anxious anticipation of being ridiculed and rejected by his guards — often guards of his own making.”

Getting into character

More than 40 years later, the Stanford Prison Experiment is often cited as proof of man’s inhumanity to man. That it was conducted 10 years after the infamous Milgram experiment — in which volunteers were induced to administer electric shocks to other volunteers who couldn’t answer questions correctly, no matter how much agony they were causing — only added to its legitimacy.

A prisoner with guard John Loftus, during the experiment in 1971.Photo: Corbis

But how legitimate was it? Dave Eshelman, now 62, was one of Zimbardo’s guards — in fact, he was the guard that came to be known as “John Wayne,” the most authoritative and fearsome of them all. But he didn’t start out that way.

“That first day was very mellow,” Eshelman tells The Post. “It was so mellow that I made the decision to get something started. My thinking was, ‘Somebody’s paying a lot of money for this experiment and nothing’s happening. They must be trying to prove that prison’s a bad environment, so I’m gonna make it a bad environment.’ So I took on this tough-guy persona based on ‘Cool Hand Luke’ and the fraternity hazing I’d endured the previous year.”

Eshelman became the ringleader, and says most of the stuff he had the prisoners do was fairly harmless. “You line people up, shout at them, get them to get down and do 20 push-ups, have one prisoner turn to another and shout out ‘I LOVE YOU’ or something that would embarrass them,” he says.

Eshelman was taking acting classes, and he looked at his role as an improv opportunity.

“Keep in mind that everyone knew we were being photographed and filmed,” he says. “Sometimes we could hear Zimbardo and the other professors through the walls. At one point, Zimbardo came over and told me I was doing a great job.”

It was Eshelman who had that fateful conversation with Zimbardo’s girlfriend, and even today he’s perplexed by her reaction. “When she saw me become a guard, she saw me become a cruel and sadistic person,” he says. “But what I was doing when I was talking to her was getting into character.”

It wasn’t real

From left; Billy Crudup as Dr. Philip Zimbardo, Nelsan Ellis as Jesse Fletcter, and James Wolk as Mike Penny in “The Stanford Prison Experiment.”Photo: IFC

Eshelman’s not the only participant to have spoken of the experiment’s deep, inherent flaws.

“I think Zimbardo wanted to create a dramatic crescendo, and then end it as quickly as possible,” prison guard John Mark told Stanford Magazine. “He knew what he wanted and then tried to shape the experiment — by how it was constructed, and how it played out — to fit the conclusion that he had already worked out. He wanted to be able to say that college students, people from middle-class backgrounds — people will turn on each other just because they’re given a role and given power . . . I think that was a real stretch.”

And then there was Zimbardo’s prison expert, the SPE’s chief consultant Carlo Prescott, who in 2005 described himself in the Stanford Daily as “an African-American ex-con who served 17 years in San Quentin for attempted murder.” Zimbardo mined him for information.

Prescott wrote that all of the abuses perpetrated by the guards were his ideas, based on his time at San Quentin: “To allege that all these carefully tested, psychologically solid, upper-middle-class Caucasian ‘guards’ dreamed this up on their own is absurd.”

Even before those involved with the SPE spoke out, Zimbardo was criticized by the field’s most prominent thinkers. In 1973, famed German psychologist Erich Fromm tore the experiment apart. In his book “The Anatomy of Human Destructiveness,” Fromm wrote that the SPE was contaminated from the beginning: the “prisoners” were arrested by real officers; they were made to wear clothing unlike any true inmates; the volunteers were self-selecting, and all of one class and race (save one Asian participant); most guards did not abuse the prisoners, and in fact some displayed acts of kindness.

Most crucially, all were aware they were in a mock prison, and were unduly subjected to “overt demand characteristics” — knowing what was expected of them and playing to those very expectations.

A methodological analysis published in American Psychologist in February, 1975 came to the same conclusion: the study was flawed, from conception to execution. Moreover, SPE has never been published in a mainstream journal, and never been subjected to peer review.

Good theater

Professor Peter Gray, who taught psychology at Boston College for 30 years, is another prominent critic — in fact, he refused to include the Stanford Prison Experiment in his famous textbook “Psychology,” now in its sixth edition.

“I really see [the SPE] as play-acting,” Gray tells The Post. “Studying real prisons and prison guards — that’s much harder, right? It’s not as sexy. Everyone in the SPE was being asked to play a certain role. The ones who improvised were called sadists — but you could just say that they’re getting into the spirit of the thing.” He laughs. “It’s absurd,” he says. “It’s funny. It really is.”

That’s exactly what Eshelman — considered the worst of them all — has maintained all along. “It was good theater,” he says. “I’m not sure it was good science.”