The study in question by Kundermann, which was published in 2004 in the journal Psychosomatic Medicine, found that people who were deprived of sleep for one night had an increased sensitivity to certain types of pain. Two Justice Department memos, dated May 10, 2005, cited this study as justification to conclude that severe sleep deprivation of up to 180 consecutive hours might cause some increased pain but not "severe physical pain" when used in conjunction with facial slaps, stress positions, water dousing and walling, in which a detainee is slammed against a flexible wall.
"Because sleep deprivation appears to cause at most only relatively moderate decreases in pain tolerance, the use of these techniques in combination with extended sleep deprivation would not be expected to cause severe physical pain," wrote Steven Bradbury, a principal deputy assistant attorney general in the Office of Legal Counsel, who authored the memos.
Kundermann, who found out about the CIA's use of his work from a TIME reporter, said his research did not justify the Justice Department's conclusion. "We were working with healthy volunteers and didn't deprive them of sleep for more than one day without allowing them to recover," he said. "Even under these circumstances, certain changes can occur, such as hallucinations, depending on the individual's condition."