A line of prisoners shuffled along the corridor, ankles shackled together and brown paper bags over their heads.
Marshalling them along were khaki-clad guards, barking obscenities at them from behind silver aviator sunglasses.
The detainees' shoulders were slumped and heads bowed. The guards had subjected them regularly to humiliating and degrading sexual abuse.
But despite all of the similarities, this was not Abu Ghraib. This was a basement in Stanford University in 1971.
In what has become known as the Stanford Prison Experiment, a handful of bright and optimistic university students were transformed in just six days into a gang of sadistic prison guards who were determined to "break" their fellow classmates.
Fearing an escalation of abuse, the study was called off early by the man who had orchestrated it, psychologist Philip Zimbardo.
The findings of the experiment shocked the world. It proved that under certain circumstances, ordinary decent people could be led to commit the same atrocities that were committed in Nazi Germany.
So when, in 2004, Zimbardo saw bags placed over the heads of Iraqis in Abu Ghraib prison and them being subject to humiliating and abhorrent torture, he immediately saw the parallels.
"Many of the pictures that were shown were similar if not more extreme than what the guards did to the prisoners in my experiment," he said.
The torture was indeed more extreme. In reported cases, detainees were urinated upon, smeared with excrement and forced to pose for pictures. In some examples, detainees were sodomised with batons.
At the time the abuses were blamed by the US military on a handful of individuals but Zimbardo believes the soldiers were placed under very special circumstances – circumstances that can make even the most decent people commit the most heinous crimes.
He became convinced that the soldiers in Abu Ghraib were not entirely responsible for their own actions and later decided to represent one of the men, Staff Sergeant Ivan "Chip" Frederick in his court martial.
Zimbardo said: "When Bush and the military blamed the abuse on a few bad apples I immediately became suspicious. I argued that the apples were good. It was the barrel in which they were placed that was bad.
"I had populated my prison with only good apples and put them in a environment which was designed to bring out the worst in them.
"I got access to all the notes and documents from Abu Ghraib and I can say unequivocally that it was the situation that caused the soldiers to act in the way they did."
To prove his point, Zimbardo went back to his original experiment and transcribed the dialogue between guards and prisoners for his new book, The Lucifer Effect.
"In my experiment guards were not allowed to use force so all of the abuse was mental and emotional," he said. "The evil was in the words that were used."
Seventy-five people answered the original advert Zimbardo placed in a college newspaper, where a dozen people had the opportunity to be paid $15 a day to take part in a psychological experiment lasting two weeks.
The 75 were then subjected to psychological tests to ensure that they were mentally stable and the healthiest were picked out.
The lower basement of Stanford University was transformed into a prison and individuals were selected at random to play either prisoners or guards.
Prisoners were stripped naked to be deloused by guards who began what Zimbardo calls the "degradation process" by mocking their genitalia. However the mood early on was of a college summer camp, until on day two the prisoners staged a rebellion.
Many of the students came from a background of activism against the Vietnam War and disliked authority. Zimbardo said that the rebellion was inspired by that background as well as a habit of verbally abusing the guards.
The ringleader of the rebellion, Doug Korpi, or prisoner 8612 as he was known to guards, was singled out in particular and was placed in solitary confinement (the hole).
When he sought an early exit Zimbardo, acting in his position as prison superintendent, offered him better treatment in return for playing snitch on his fellow prisoners. He returned to tell his fellow inmates that there was no way out.
However he got his wish the following day after appearing to suffer a breakdown.
In order to "up the ante" the guards became increasingly sadistic and started to wake the prisoners in the middle of the night to perform menial tasks, such as cleaning the toilet with their hands.
The next prisoner to crack was 819. As he talked to Zimbardo about wanting to leave he could hear prisoners behind him chanting "Prisoner 819 did a bad thing". He began to weep and told Zimbardo that he wanted to go back to prove to his fellow inmates that he wasn't a bad prisoner.
"Listen carefully to me, you're not 819," Zimbardo told him.
"You are Stewart and my name is Dr Zimbardo. I am a psychologist not a prison superintendent, and this is not a real prison."
He said that the effect was like watching a "fog clearing from his eyes".
He was astonished that after three days the student's thoughts had warped so much that he actually believed that he was a prisoner.
His exit left a gap in the prison and he was replaced by Clay Ramsay—prisoner 416. When he arrived he was immediately targeted by the guards and prisoners warned him that there was no leaving. "I knew by the first evening that I had done something foolish to volunteer for this study," he was quoted as saying.
By this time, one of the guards, 18-year-old Dave Eshleman had already gained the nickname "John Wayne" because of his aggressive tactics.
He wakes prisoners up in the middle of the night and shouts abuse in their faces. He forces them to play leapfrog only in their smocks, their genitals exposed.
"He was creative in his evil," Zimbardo said. "He would think up ingenious ways of degrading prisoners."
It was when Zimbardo's then girlfriend and future wife Christina Maslach came to visit him that things changed. She said that watching the shackled prisoners be paraded along the corridor dehumanised with bags on their heads "sickened her". An argument ensued and she said that she began to question Zimbardo's character and the basis of the relationship.
The next morning Zimbardo ends the experiment.
He said that he was "ashamed" for allowing the experiment to continue as long as it did. "I allowed those terrible things to go on. I should've stopped it. I got sucked into my role as prison supervisor and allowed this to go on."
He said that there were too many parallels between his experiment and Abu Ghraib to go unnoticed. In both cases prisoners were dehumanised, stripped naked like animals and had their faces obscured by bags.
Similarly in Abu Ghraib guards removed all identifying features from their uniforms and in Stanford, guards wore sunglasses that obstructed their eyes.
In both cases prisoners were sexually degraded. In Abu Ghraib they put simulated fellatio; in Zimbardo's experiment they simulated sodomy.
In both cases the abuse only took place with no supervision. In Stanford the worst abuses were committed on the night shift, in Abu Ghraib they took place in an isolated area of the prison where no senior officers ever went.
Zimbardo said that the CIA were to blame by putting pressure on the soldiers to break the prisoners as a way of softening them up for interrogation and then purposefully leaving them unsupervised.
Speaking about how the abuse escalated to such a point in his experiment, he said: "Each day serves as a platform for what happens the next day. The guards wanted to have more and more power. It got worse and worse over time and the guards began to abuse the prisoners even more.
He added: "Boredom is a major motivation for evil. The guards used them as their playthings."
Dr Zimbardo's new book, The Lucifer Effect was published last Thursday and is available on Amazon.com.
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