The extreme stress of torture harms the memory
Torture techniques used on suspected terrorists by the Bush administration may have failed to get to the truth, researchers say.
Professor Shane O'Mara of Trinity College, Dublin, said the interrogation techniques had a detrimental effect on brain functions related to memory.
He listed 10 methods of what he called torture used by the US, including stress positions and waterboarding.
His review is published in the journal, Trends in Cognitive Science.
'Lack of control'
Professor O'Mara said US Department of Justice memos released in April showed that the Americans believed that prolonged periods of shock, anxiety, disorientation and lack of control were more effective than standard interrogation in extracting the truth.
He said: "This is based on the assumption that subjects will be motivated to reveal truthful information to end interrogation, and that extreme stress, shock and anxiety do not impact on memory.
Techniques used by US
Walling - captive is placed with heels touching the wall and is pulled away and pushed back into it with force
Wall standing - captive stands four to five feet from wall with fingertips supporting all the body weight to induce muscle fatigue
Cramped confinement - captive place in small box in darkness for up to two hours, in a larger box for up to 18 hours
Sleep deprivation - captive is deprived of sleep for up to 11 days
Stress positions - captive sits on floor with legs straight out in front and arms raised above head or is made to kneel on the floor while leaning back at a 45 degree angle
Waterboarding - captive is bound head down on an inclined bench with a cloth over the eyes. Water is applied to the cloth for 20 to 40 seconds at a time inducing fast breathing and perception of drowning
"However this model of the impact of extreme stress on memory and the brain is utterly unsupported by scientific evidence."
He said studies of extreme stress with special forces soldiers had found that their recall of previously learned information was impaired afterwards.
"Waterboarding in particular is an extreme stressor and has the potential to elicit widespread stress-induced changes in the brain."
Professor O'Mara said contemporary neuroscientific models of human memory showed that the hippocampus and prefrontal cortices of the brain were very important.
The stress hormone, cortisol, binds to receptors in the hippocampus and prefrontal cortex increasing neuronal excitability which compromises the normal functioning of the brain if it is sustained.
And other stress hormones called catecholamines could lead to an increase in blood pressure and heart rate which could cause long-term damage to the brain and body if they were maintained at a high level for a long time.
Professor O'Mara said a common argument in favour of torture was that it would reliably elicit truthful information from the captive's long-term memory.
But psychological studies had suggested that during extreme stress and anxiety, the captive would be conditioned to associate speaking with periods of safety.
And because torture was stressful for the torturers the fact that the captive was speaking also provided a safety signal to the captor.
"Making the captive talk may become the end - not the truth of what the captive is revealing.
"These techniques cause severe, repeated and prolonged stress, which compromises brain tissue supporting memory and executive function.
"The fact that the detrimental effects of these techniques on the brain are not visible to the naked eye makes them no less real."
Dr David Harper, a clinical psychologist from the University of East London, said the study appeared to be consistent with previous research on memory and trauma and with evidence of previous torture survivors and those in the intelligence community critical of psychological torture techniques.
"Believers in coercive interrogation tend to believe that people will 'tell the truth' as a result but much evidence suggests that people will, in fact, tell those conducting the torture what they think will make the torture stop.
"This has been noted as a danger by commentators from the Spanish Inquisition, through the Moscow Show Trials of the 1930s to the present day."
Dr Stuart Turner of the Centre for the Study of Emotion and Law said: "There is now very strong evidence that torture and harsh interrogation techniques may disrupt normal memory processes.
"With this in mind, it is also unreasonable to expect torture survivors to be able to give consistent and complete accounts of their experiences.
"This is highly relevant, for example, to the process of decision making for asylum seekers, arriving in the UK seeking refuge and for whom credibility is often a central issue.
"It appears that O'Mara's review paper supports the contention that to expect consistent memories in asylum applicants is unreasonable and therefore that inconsistencies should certainly not automatically be interpreted as evidence of fabrication."