Interrogators have centuries of experience extracting information from the unwilling. Medieval inquisitors hanged heretics from ceilings. Salem magistrates used fire to elicit witchcraft confessions. And CIA officers waterboarded terrorism suspects in clandestine prisons.

Yet it has not settled a debate as old as interrogation itself: Does torture work?

Secret Justice Department memos released last week, revealing the CIA's harshest interrogation methods, do little to resolve the question. The memos credit waterboarding, face slapping, sleep deprivation and other techniques for producing the country's best intelligence following the Sept. 11, 2001, terrorist attacks. They also note that nonviolent tactics more often were successful than violence.

President Barack Obama, who ordered the memos released, said Tuesday they showed the United States "losing our moral bearings." He did not, however, say whether he believed the tactics worked.

In 2006, a group of scientists and retired intelligence officers set out to settle the matter. They sought to find the most effective interrogation tactics and advise the U.S. government on their use. Their conclusions, laid out in a 372-page report for the director of national intelligence, argued against harsh interrogation.

"The scientific community has never established that coercive interrogation methods are an effective means of obtaining reliable intelligence information," former military interrogation instructor and retired Air Force Col. Steven M. Kleinman wrote in the Intelligence Science Board report. "In essence, there seems to be an unsubstantiated assumption that 'compliance' carries the same connotation as 'meaningful cooperation.'"

In short: Slam someone up against the wall, keep him awake for days, lock him naked in a cell and slap his face enough, and he will probably say something. That doesn't necessarily make it true.

Former Vice President Dick Cheney has long maintained that the CIA's harshest interrogation tactics, which the U.S. now considers torture, prevented terrorist attacks and saved lives on President George W. Bush's watch after Sept. 11. He called on the Obama administration to release documents showing that success.

The documents, which are referenced in the Justice Department memos, say the interrogation program "has been a key reason why al-Qaida has failed to launch a spectacular attack in the West since 11 September 2001."

National Intelligence Director Dennis Blair, Obama's top intelligence adviser, told intelligence personnel in an April 16 letter _ the same day the Justice Department memos were released _ that "high-value information came from interrogation in which those methods were used and provided a deeper understanding of the al-Qaida organization that was attacking the country."

In a statement issued Tuesday night, Blair backed away from what appeared to be an endorsement of the techniques' effectiveness.

"The information gained from these techniques was valuable in some instances, but there is no way of knowing whether the same information could have been obtained through other means," he said. "The bottom line is these techniques have hurt our image around the world, the damage they have done to our interests far outweighed whatever benefit they gave us and they are not essential to our national security."

Intelligence from Khalid Sheikh Mohammed and Abu Zubaydah, two detainees who were waterboarded, led to the discovery of a terrorist cell, the capture of other suspected terrorists and an understanding of the terrorist network, the documents say.

Darius Rejali, a Reed College political scientist who studies torture, is dubious of such claims. The British claimed that tough interrogation of Irish Republican Army suspects thwarted dozens of terrorist attacks, Rejali said, but evidence later proved the intelligence was often useless.

"When the data comes it's usually just incredibly embarrassing," Rejali said.

Elsewhere in the Justice Department documents, there are suggestions that the toughest tactics weren't always the most successful. Of the 94 terrorist suspects in the CIA program, only 28 were subjected to "enhanced" methods, the documents said. That means two out of three detainees gave up valuable intelligence in simple interviews.

When the CIA decided to use waterboarding _ a tactic that simulates drowning _ officials ended up using it far more than intended. Abu Zubaydah was waterboarded at least 82 times in August 2002, the documents said. Khalid Sheikh Mohammed, the admitted mastermind of the 9/11 attacks, was waterboarded 183 times in March 2003.

"You keep thinking, 'Maybe one more time, and one more time," Rejali said, explaining how interrogators ramp up their methods even as their effectiveness wanes.

If such tactics are unreliable, why would CIA officers, Justice Department lawyers and the White House all sign off on seven days of sleep deprivation, locking detainees in wooden boxes, forced nudity and simulated drowning?

The answer, Rejali said, is the same one that explains so much in Washington: bureaucracy.

"The correct answer for a bureaucrat is always to torture, even if you know it doesn't work," Rejali said. "Nobody wants to be the guy who could have done something and then didn't do it."

The stress CIA officers were facing is clear from the Justice Department memos. Khalid Sheikh Mohammed taunted his interrogators when asked about planned attacks: "Soon, you will know."

Tensions were high, the country was in the midst of one war and on the brink of another. "And we suspended the whole idea of quality control," said Jack Cloonan, a former member of the FBI's Osama bin Laden unit. When interrogators asked for permission to ramp up their interrogations, Washington signed off.

The lawyers sidestepped some thorny questions, such as the consequences of using tactics the U.S. has condemned in Egypt, Iran and Syria. They repeatedly approved the interrogation policies.

"They're suits, They're sitting at desks in Washington trying to find a way to allow things to happen, to provide a legal basis," Cloonan said. "It has nothing to do with the effectiveness of these techniques."

Releasing the memos and changing U.S. interrogation policy was relatively easy for the Obama administration. The real test will come after a terrorist attack, a threat against the United States or the capture of bin Laden, when the CIA comes to the White House and asks the president what it is allowed to do.

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Associated Press writer Pamela Hess contributed to this report.