Though waterboarding proved to be the most controversial interrogation technique used on prisoners held by the CIA, the most effective turned out to be sleep deprivation. In the wake of President Obama's new prohibition on harsh interrogation methods, sleep deprivation—a method preferred by many in the CIA—is forbidden, and many are lobbying hard for its reinstatement. According to the Los Angeles Times, CIA interrogators forced over 25 detainees to remain awake, sometimes for 11 days, and found the punishment to "enable" all other methods without harming the prisoner. The detainees would often be shackled standing up in such a way that when they began to doze off their chains would startle them awake. However, many critics are pointing out that the CIA's enthusiasm for sleep deprivation only highlights their twisted logic. "Just because the pain of sleep deprivation 'can't be measured in terms of physical injury or appearance . . . does not mean that the mental anguish is not as bad," one sleep expert said. A task force is currently considering whether the technique could be employed in the future.