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Study: torture produces unreliable information

Sept. 21, 2009
Courtesy Cell Press
and World Science staff

Harsh in­ter­roga­t­ion tech­niques used by U.S. agents un­der Pres­ident George W. Bush probably failed to ex­tract much truth­ful in­forma­t­ion from ter­ror­ist sus­pects, a new study con­cludes.

The tor­ture, as many ex­perts have called these meth­ods, probably caused un­in­tend­ed dam­age to sus­pects’ mem­o­ry and brain func­tions, com­pro­mis­ing the re­li­a­bil­ity of their state­ments, the re­search sug­gests.

The claims are based on a re­view of past re­search pub­lished Sept. 21 in the re­search jour­nal Trends in Cog­ni­tive Sci­ence.

Memos re­leased by the U.S. Jus­tice De­part­ment last April sug­gest pro­longed shock, stress, anx­i­e­ty, dis­o­ri­enta­t­ion and lack of con­trol work bet­ter than stand­ard in­ter­roga­t­ion tech­niques to make sub­jects re­veal truth­ful in­forma­t­ion.

But “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 mem­o­ry,” said the au­thor of the new re­view, neu­ro­sci­ent­ist Shane O’­Mara of Trin­ity Col­lege in Dub­lin. These as­sump­tions are “un­sup­ported by sci­en­tif­ic ev­i­dence,” he added.

“To briefly sum­ma­rize a vast, com­plex lit­er­a­ture, pro­longed and ex­treme stress in­hibits the bi­o­log­i­cal pro­cesses be­lieved to sup­port mem­o­ry in the brain,” said O’­Mara. “For ex­am­ple, stud­ies of ex­treme stress with Spe­cial Forc­es Sol­diers have found that re­call of previously-learned in­forma­t­ion was im­paired af­ter stress.” 

Wa­ter­board­ing, a form of sim­u­lat­ed drown­ing, in par­tic­u­lar is an ex­treme stres­sor and can elic­it wide­spread stress-induced changes in the brain, O’­Mara con­tin­ued.

Psy­cho­log­i­cal stud­ies sug­gest that se­verely stressed cap­tives are con­di­tioned to as­so­ci­ate speak­ing with pe­ri­ods of safe­ty, O’­Mara said. For the cap­tor, get­ting the cap­tive talk­ing al­so of­fers some re­lief from the un­sa­vory task of ad­min­is­ter­ing the stress. Thus it is hard or im­pos­si­ble to de­ter­mine dur­ing the in­ter­roga­t­ion wheth­er the cap­tive is re­vealing truth­ful in­forma­t­ion or just talk­ing to es­cape tor­ture.

Re­search has al­so shown that ex­treme stress harms the brain’s front­al lobe and is as­so­ci­ated with pro­duc­tion of false mem­o­ries, O’­Mara added. Stud­ies have found that the hip­po­cam­pus and prefront­al cor­tex, brain re­gions in­te­gral to mem­o­ry, are af­fect­ed by hor­mones ac­ti­vat­ed by stress and sleep de­priva­t­ion, O’­Mara said. These hor­mones have been shown to have harm­ful ef­fects on mem­o­ry, he added.

“Given our cur­rent cog­ni­tive neurobi­o­log­i­cal knowl­edge, it is un­likely that co­er­cive in­ter­roga­t­ions in­volv­ing ex­treme stress will fa­cil­i­tate re­lease of truth­ful in­forma­t­ion,” O’Mara wrote. “On the con­tra­ry, these tech­niques cause se­vere, re­peat­ed and pro­longed stress, which com­pro­mises brain tis­sue sup­porting both mem­o­ry and de­cision­mak­ing.”


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Harsh interrogation techniques used by U.S. agents under President George W. Bush probably failed to extract truthful information from terrorist suspects, scientists say. The torture, as many experts have called these methods, probably caused unintended damage to suspects’ memory and brain functions, compromising the reliability of their statements, the researchers say. The claims are based on a review of past research published Sept. 21 in the research journal Trends in Cognitive Science. Memos released by the U.S. Justice Department last April suggest prolonged shock, stress, anxiety, disorientation and lack of control work better than standard interrogation techniques to making subjects reveal truthful information. But “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 memory,” said the author of the new review, neuroscientist Shane O’Mara of Trinity College in Dublin. These assumptions are “unsupported by scientific evidence,” he added. “To briefly summarize a vast, complex literature, prolonged and extreme stress inhibits the biological processes believed to support memory in the brain,” said O’Mara. “For example, studies of extreme stress with Special Forces Soldiers have found that recall of previously-learned information was impaired after stress occurred.” Waterboarding, a form of simulated drowning, in particular is an extreme stressor and has the potential to elicit widespread stress-induced changes in the brain, O’Mara continued. Psychological studies suggest that severely stressed captives are conditioned to associate speaking with periods of safety, O’Mara said. For the captor, getting the captive talking also offers some relief from the unsavory task of administering the stress. Thus it is hard or impossible to determine during the interrogation whether the captive is revealing truthful information or just talking to escape torture. Research has also shown that extreme stress harms the brain’s frontal lobe and is associated with production of false memories, O’Mara added. Studies have found that the hippocampus and prefrontal cortex, brain regions integral to memory, are affected by hormones activated by stress and sleep deprivation, O’Mara said. These hormones have been shown to have harmful effects on memory, he added. “Given our current cognitive neurobiological knowledge, it is unlikely that coercive interrogations involving extreme stress will facilitate release of truthful information,” O’Mara wrote. “On the contrary, these techniques cause severe, repeated and prolonged stress, which compromises brain tissue supporting both memory and decisionmaking.”