By Ryan Dilley
Photographs appearing to show a British soldier abusing an Iraqi man may still prove false, but coalition troops have certainly mistreated captives on other occasions. Should we be surprised?
"Their boredom had driven them to ever more pornographic and degrading abuse of the prisoners," said a horrified psychologist, Philip Zimbardo.
This exclamation of disgust was not directed at the US soldiers who took snapshots of Iraqi prisoners squirming naked at Abu Ghraib jail in Baghdad. Nor was it directed at British servicemen allegedly photographed first urinating on and then beating a captive in a lorry in southern Iraq.
Professor Zimbardo was instead disturbed by the spiralling sadism of group of ordinary male students he had recruited to play prison guards in a two-week scientific study he had devised.
So cruelly did some of the young men begin to treat the inmates - also students picked at random from a pool of sane volunteers - that Zimbardo closed his "prison" after just six days.
The Stanford Prison Experiment - conducted in 1971 - is seen as a breakthrough in understanding how ordinary, decent people can sometimes behave with extraordinary malice.
"It's a touchstone," says Professor David Wilson, a criminologist, who once governed some of the UK's most challenging prisons.
"If you give a person power over someone who is powerless, someone who has been demonised or made to seem less human, then that absolute power corrupts absolutely."
Professor Wilson says that in devising a humane regime for a unit housing particularly violent offenders at Woodhill Prison, he took care to remind his warders that the hostile inmates were still deserving of dignified treatment.
"I had to be really be up-front about what was acceptable and unacceptable behaviour in a situation in which professionalism could have easily been forgotten."
He says that the disturbing photos of hooded Iraqi prisoners in Abu Ghraib prison - pictures whose authenticity is not in doubt - suggest that some American jailers had crossed this line and were dehumanising their charges.
"By hooding the prisoners, by hiding their faces, they were denying them individuality. This makes abusive treatment more likely. Just as very violent offenders often mask the faces of their victims before carrying out attacks."
ABUSE AT ABU GHRAID
Detainees were threatened with a loaded pistol
Cold water was poured on naked prisoners
Inmates were beaten with a broom handle and chair
Male detainees were threatened with rape
Male detainees were forced to wear women's underwear
Source: Pentagon report
Those linked to the photographs were reservists (even a man who is a prison officer in civilian life), not hardened fighters. So is there the potential for such barbarity present in us all?
"Not every person would act like that," says historian Christopher Browning, who researched the activities of a group of unremarkable World War II German reservists - who went on to massacre many thousands of Jewish villagers with little or no coercion from their officers.
The men were not Nazi zealots fired by anti-Semitic hatred, nor were they career soldiers hoping to impress their superiors with their aggression, and yet they committed horrific and bloody war crimes.
"Not all the reservists went along with the killings. But the majority of ordinary people can be induced to go along with a group."
The situation in Iraq bears no resemblance to the war crimes of World War II, but Mr Browning says that ordinary people can all too easily adopt the brutal "guard culture" seen in the Stanford experiment.
"You have to work very hard with a lot of training and supervision to stop this culture spinning out of control."
Mr Browning notes that the US troops were not made callous by battlefield trauma. "This wasn't battlefield frenzy, where discipline breaks downs in the heat of war. These weren't combatants, taking sniper fire in Fallujah."
He argues that it is more subtle signals from very senior figures which can have the most profound effect on the behaviour of soldiers on the ground, setting the scene for abuse without explicitly ordering it.
"In the War on Terror, the US has set limits on the Geneva Convention to minimise the protections it offers, think of Guantanamo. These things filter down from the very top."
Mr Browning says that by casting military captives not as prisoners of war, but as continuing threats and sources of information "it was predictable that these abuses would occur".
Donning a military or any other uniform can increase the risks of just such a sliding of personal morals, says Dr Andrew Silke, lecturer in police studies at the University of Leicester's Scarman Centre.
"Psychology has long known that groups are very dangerous. People can do things in a group they'd never do as an individual. They can do an awful lot of damage because the constraints they feel are diminished."
But psychologist Dr Patrick Tissington - himself a former British Army officer - says that the military can use loyalty to a group to encourage decent, rather than brutal behaviour.
He says that "without supervision, the Stanford guards quickly turned into nasty pieces of work", but where members feel a great loyalty to a group and a concern for the standing of that organisation they will want to behave impeccably.
Dr Tissington says that soldiers will frame their own behaviour so as not to bring shame on their comrades, their predecessors, nor the recruits to come. The British regimental system has long been praised for binding soldiers very tightly to small units with long histories and traditions.
Such a burden of expectation may be vital. The Stanford experiment came to some grim conclusions: "About a third of the guards were hostile, arbitrary, and inventive in their forms of prisoner humiliation. These guards appeared to thoroughly enjoy the power they wielded, yet none of our preliminary personality tests were able to predict this behaviour."