President Donald Trump has repeatedly said that waterboarding “works.” But scientists say otherwise. Research has shown that the stress and pain caused by techniques like waterboarding can hinder a person from recalling information.

The president, who made similar claims on the campaign trail, said in a Jan. 25 interview with ABC News’ David Muir when asked about waterboarding, “Absolutely I feel it works.” He said that “I have spoken to others in intelligence. And they are big believers in, as an example, waterboarding. … Because they say it does work. It does work.”

A day later, in a Jan. 26 interview with Fox News’ Sean Hannity, Trump called waterboarding “just short of torture,” and said, “I will tell you, though, it works. And I just spoke to people who told me it worked, and that’s what they do.” Trump and Hannity also agreed that neither of them had “even a doubt that it works.”

Trump, Jan. 26, Fox News: And I watch these people in television, “Oh, Donald Trump is in favor of torture.” Look, we have people that knocked down the World Trade Center, we have people that go into a club and they blow everyone up. … They go into a club and they machine gun everybody down. And then, they, we’re not allowed to waterboard? It’s so — it seems so foolish and so naive. But this is what we have to put up with. But here’s the story — Fox News’ Sean Hannity: I would ask [ABC News’] David Muir, if they kidnapped your kid and you have one of the kidnappers, what would you do to get the location of your child? Trump: Or would you want him to talk in 48 hours from now by being nice to him, OK?

And yet again on Jan. 27, Trump said, “I happen to feel that it does work,” referring to “torture or waterboarding or however you want to define it — enhanced interrogation I guess would be a word.”

Despite Trump’s belief in waterboarding, he said in all three instances that he would follow the advice of his defense secretary, James Mattis. Trump also told ABC News that he “will rely on” the advice of Mattis and Mike Pompeo, recently confirmed to lead the CIA, and others. He added, “If they don’t wanna do, that’s fine. If they do wanna do, then I will work for that end.”

After Trump’s recent remarks, Defense Department spokesman Navy Capt. Jeff Davis told reporters: “Secretary Mattis said in his confirmation process that he will abide by and is committed to upholding international law, the Law of Armed Conflict, Geneva Conventions and U.S. law, and that has not changed.”

The United Nations Convention Against Torture defines “torture” as “any act by which severe pain or suffering, whether physical or mental, is intentionally inflicted on a person for such purposes as obtaining from him or a third person information or a confession.” The Detainee Treatment Act of 2005 prohibits “cruel, inhuman, or degrading treatment or punishment of persons under custody or control of the United States government,” and required detainees in Iraq to be afforded all the protections of the Geneva Conventions and the U.N. Convention Against Torture.

In 2015, then-President Obama also signed a defense bill that included language codifying a 2009 executive order, which prohibits U.S. interrogators from using techniques not authorized and listed in the United States Army Field Manual on interrogation practices.

During his nomination hearing on Jan. 12, Pompeo said he would “absolutely not” revive the agency’s use of the practice of “enhanced interrogation,” which included waterboarding and other inhumane treatment. Yet just a few days later, he said he was open to changing that policy if “experts” believed the current law impeded “gathering vital intelligence.”

This isn’t the first time Trump has claimed torture techniques “work.” On the campaign trail in July, he said “enhanced interrogation … works.”

“Enhanced interrogation” includes techniques such as slapping a person in the face, sleep deprivation, cramped confinement and waterboarding — the last of which involves reducing airflow with water to trigger the feeling of drowning.

In February, Trump also claimed “torture works,” adding that waterboarding is a “minor form” of torture and that “we should go much stronger than waterboarding.”

Research in neuroscience and psychology goes counter to Trump’s claim.

As we explained during the presidential campaign, Shane O’Mara, a brain researcher at Trinity College Dublin in Ireland, published a review of the scientific studies on this topic in Trends in Cognitive Sciences in 2009. O’Mara wrote that “[s]olid scientific evidence” suggests enhanced interrogation is “unlikely to do anything other than the opposite of that intended.”

Researchers have found that the neural mechanisms and areas of the brain, like the frontal lobe, that are vital to memory formation and recall are disrupted — even damaged permanently — after periods of extreme and prolonged stress and pain, explains O’Mara. Stress causes the release of hormones like cortisol, which impair the function of these brain regions, and in turn, cause people to have trouble recalling both short- and long-term memories.

It may also be troublesome to determine “whether the information that a suspect reveals is true,” argues O’Mara. The information “presented by the captor to elicit responses during interrogation might inadvertently become part of the suspect’s memory,” he says.

O’Mara’s argument relies on the science behind confabulation, or the production of false memories. Confabulation is a common symptom of people who have frontal lobe disorders, the area of the brain that’s vital to memory formation and recall.

Amy F. T. Arnsten, an expert at Yale in both neuroscience and psychology, reviewed both human and animal studies that looked at the effect of stress on the prefrontal cortex, a part of the frontal lobe. She writes in a 2009 paper published in Nature Reviews Neuroscience: “Even quite mild acute uncontrollable stress can cause a rapid and dramatic loss of prefrontal cognitive abilities, and more prolonged stress exposure” can permanently change the structure of the region for the worse.

In addition, the Senate Select Committee on Intelligence released a report in 2014 that concluded, “The CIA’s use of its enhanced interrogation techniques was not an effective means of acquiring intelligence or gaining cooperation from detainees.” The report, which was approved in 2012 by a 9-6 committee vote when the Democrats were in control of the Senate, added, “The CIA’s justification for the use of its enhanced interrogation techniques rested on inaccurate claims of their effectiveness.”

Editor’s Note: SciCheck is made possible by a grant from the Stanton Foundation.