The CIA water-boarded al-Qaida masterminds Khalid Sheikh Mohammed and Abu Zubaydah a combined 266 times. Doesn't water-boarding lose its effectiveness once the prisoner knows he isn't going to drown?
Not really. Coercive interrogation does not require the perception of imminent death. Many historical torture techniques, such as prolonged standing and high-cuffing, are simply painful. Prolonged oxygen deprivation and the ingestion of huge amounts of water will, indeed, cause the victim pain, although his body may adapt such that it takes a little more water or a little more time to produce a constant level of discomfort. Then there's the body's natural response to the stress, which is very unpleasant on its own terms. Even a prisoner who is convinced his life is not in danger would be susceptible to this effect. At best, a highly trained victim would be able to moderate his body's response slightly.
Water-boarding affects the digestive and respiratory systems. As the victim ingests more and more water, his intestines swell, which produces a burning sensation. This effect lessens somewhat with repeated exposure, as the digestive organs stretch; interrogators can avoid this by using more water.
The respiratory system is not as resilient to the torture. Oxygen deprivation—the direct effect of water-boarding—causes a panoply of physical effects, like bleeding from the nose and ears and under the skin. Hypoxia also triggers a secondary stress response: Even if you're not consciously fearing for your life, your body will react as though you were and release norepinephrine and cortisol. These stress hormones can produce unpleasant side effects like intense asthma and a racing heart. A calm and confident victim may have a less-acute stress response. On the other hand, an experienced victim might just as well have the opposite reaction—he may be so traumatized by the mere sight of the water-board that his stress response is heightened.
The CIA was attempting to take advantage of this heightened stress response by repeatedly water-boarding high-value prisoners. The CIA did not use the technique as a threatened punishment for uncooperativeness. Rather, they were attempting to reduce the prisoners to a state of "learned helplessness," a condition described by psychologist M.E.P. Seligman in the 1960s. Seligman determined that a dog that has been subjected to repeated electric shocks will eventually stop trying to escape them. The CIA believed that prisoners in this psychological state would be more compliant and honest. Department of Defense memoranda repeatedly refer to establishing an attitude of helplessness in the prisoner.
Got a question about today's news? Ask the Explainer.