While we wait for Dick Cheney, the Pentagon, or the CIA to release evidence that "enhanced interrogation techniques" produced useful, truthful intelligence that could not be obtained without torture, neuroscientists are weighing in on how likely torture is to elicit such information—and they are not impressed.

It's become the conventional wisdom that the tortured will say anything to make the torture stop, and that "anything" need not be truthful as long as it is what the torturers want to hear. But years worth of studies in neuroscience, as well as new research, suggest that there are, in addition, fundamental aspects of neurochemistry that increase the chance that information obtained under torture will not be truthful.

The backstory. The inspector general of the CIA last month released a 2004 report on the interrogation of Al Qaeda suspects. As my colleague Mark Hosenballreported, it and other internal documents (which Cheney called on the CIA to release, believing they would back his claim) do not show that torture worked. In fact, The New York Times reported, the documents "do not refer to any specific interrogation methods and do not assess their effectiveness."

Scientists do not pretend to know, in any individual case, whether torture might extract useful information. But as neurobiologist Shane O'Mara of the Trinity College Institute of Neuroscience in Dublin explains in a paper in the journal Trends in Cognitive Sciencecalled "Torturing the Brain," "the use of such techniques appears motivated by a folk psychology that is demonstrably incorrect. Solid scientific evidence on how repeated and extreme stress and pain affect memory and executive functions (such as planning or forming intentions) suggests these techniques are unlikely to do anything other than the opposite of that intended by coercive or 'enhanced' interrogation."

The CIA documents released last month implicitly set forth a specific scientific rationale for enhanced interrogation: someone possesses information in his long-term memory, withholds it under normal questioning, and releases it as a result of prolonged periods of coercive interrogation. That rationale seems to be "seem based on the idea that repeatedly inducing shock, stress, anxiety, disorientation and lack of control is more effective than standard interrogatory techniques," says O'Mara, who was one of nine scientists appointed to the Panel of Experts of Ireland's Chief Scientific Adviser earlier this year.

So let's break this down anatomically. Fact One: To recall information stored in the brain, you must activate a number of areas, especially the prefrontal cortex (site of intentionality) and hippocampus (the door to long-term memory storage). Fact Two: Stress such as that caused by torture releases the hormone cortisol, which can impair cognitive function, including that of the prefrontal cortex and hippocampus. Studies in which soldiers were subjected to stress in the form of food and sleep deprivation have found that it impaired their ability to recall personal memories and information, as this 2006 study reported. "Studies of extreme stress with Special Forces Soldiers have found that recall of previously-learned information was impaired after stress occurred," notes O'Mara. "Water-boarding in particular is an extreme stressor and has the potential to elicit widespread stress-induced changes in the brain."

Stress also releases catecholamines such as noradrenaline, which can enlarge the amygdale (structures involved in the processing of fear), also impairing memory and the ability to distinguish a true memory from a false or implanted one. Brain imaging of torture victims, as in this study, suggest why: torture triggers abnormal patterns of activation in the frontal and temporal lobes, impairing memory. Rather than a question triggering a (relatively) simple pattern of brain activation that leads to the stored memory of information that can answer the question, the question stimulates memories almost chaotically, without regard to their truthfulness.

These neurochemical effects set the stage for two serious pitfalls of interrogation under torture, argues O'Mara. The first is that "information presented by the captor to elicit responses during interrogation may inadvertently become part of the suspect's memory, especially since suspects are under extreme stress and are required to tell and retell the same events which may have happened over a period of years." As a result, information produced by the suspect may parrot or embellish suggestions from the interrogators rather than revealing something both truthful and unknown to the interrogators. Second, cortisol-induced damage to the prefrontal cortex can cause confabulation, or false memories. Because a person being tortured loses the ability to distinguish between true and false memories, as a 2008 study showed, further pain and stress does not cause him to tell the truth, but to retreat further into a fog where he cannot tell true from false.

The other barrier to eliciting truthful information through torture is that the captive quickly learns that, as O'Mara puts it, "while I'm talking, I'm not being water-boarded." In other words, speaking = relief from pain. That conditions the suspect to speak at all costs, not distinguishing between what is true and what is made up. "To briefly summarize a vast, complex literature: prolonged and extreme stress inhibits the biological processes believed to support memory in the brain," says O'Mara. "Coercive interrogations involving extreme stress are unlikely, given our current cognitive neurobiological knowledge, to facilitate the release of veridical information from long-term memory."

In what is probably a futile effort to avert a flood of pro-torture comments and e-mails, let me point out that whenever science learns something about the brain, it is always possible that the generalization fails to apply to some particular brains. Maybe the brains of Abu Zubaydah, who was waterboarded 83 times, and of 9/11 mastermind Khalid Sheikh Mohammed, who was waterboarded 183 times, are different, and their torture elicited truthful information. Neuroscientists would very much like to see the evidence of that.

© 2009