In a recent television interview, President Trump stated that in order to “keep our country safe”, he intends to “fight fire with fire”, and if that includes using waterboarding and other forms of torture then so be it. Trump revealed that he had taken advice at the highest level of US intelligence, apparently asking them: “Does torture work?” with them apparently replying: “Yes.”

His Defence Secretary, retired four-star General James Mattis, and Mike Pompeo who is expected to be appointed as director of the CIA, are both proponents of torture, and both have publicly supported and defended the use of it.

Despite being prohibited worldwide, the use of torture appears to be increasing. Public debate about the use of torture currently centres on “waterboarding” – and why wouldn’t it when that’s what Trump specifically namedropped in his latest speech? The practice is one of the oldest forms of torture, where the torturer induces a sensation of drowning.

This can be achieved in a number of ways. One of the commonest ways in which this is done is by forcibly immobilising the victim, tilting the head, then placing a cloth or plastic wrap over the victim’s face and pouring water over the cloth and into the breathing passages. This might sound mild, but the effects are dramatic. The inhalation of water causes a gag reflex and the victim experiences what amounts to drowning as their body assumes that death is imminent. Waterboarding is designed to overcome the will of the individual by causing physical and psychological suffering.

Paul Ryan announces in press conference that torture is 'not' legal

The most cited argument for using waterboarding is that it is an effective method for forcing people to provide information which they would otherwise withhold. However, most psychological scientists would, in all likelihood, disagree with President Trump’s strident statement that “it works”. From a scientific perspective ,we just do not know whether waterboarding is effective.

There exist numerous anecdotal accounts of instances where important intelligence has been leveraged following the use of torture, and recently a classified CIA report has cited eight real cases of torture as evidence that the technique thwarted plots and led to the capture of terrorists. However, the latter was branded inaccurate and speculative by the US Senate Select Committee on Intelligence, and hearsay is unreliable and unverifiable.

There is no peer-reviewed empirical research on the effectiveness of torture, which leads one to question the assertion that torture works. For obvious reasons, torture does not lend itself to scientific evaluation: observing waterboarding being carried out, and testing whether it works in the laboratory or the real world, is impossible because scientists cannot effectively replicate the context or cognition of terrorists.

But psychologists and medical experts would agree that waterboarding has serious physiological and psychological responses, about which the published scientific literature is clear. In situations of extreme stress and pain (physical and psychological) human cognitive processes begin to break down, sometimes irrevocably – extreme stress and pain bring about false memories, reduce the ability to remember information, and seriously affect decision-making and memory performance.

Therefore, even if interrogators are 100 per cent sure that a detainee knows the information being sought (which is unlikely), coercive methods may in fact interfere with the quality and quantity of any information that might be forthcoming.

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Indeed, worldwide criminal justice research on false confessions provides irrefutable evidence that less coercive techniques than waterboarding have, and continue to, bring about verifiably false confessions. Khalid Sheikh Mohammed was reportedly waterboarded in excess of 180 times, which should raise questions as to whether this form of torture is effective.

If President Trump were to ask me whether torture works, as a psychological scientist, I would have to say: “I don't know.” However, I would have to point to the available science suggesting that it’s not be the best way of persuading information-holders to yield.