Why, exactly, did the United States end up torturing detainees during George W. Bush’s administration’s war on terror, when there was no scientific proof that coercive interrogations would yield valuable intelligence, and ample proof that it would harm our national security interests, elicit false information and spread unnecessary ill will throughout the Muslim world, possibly for generations to come?

It’s a head scratcher, to say the least, but a blockbuster report issued last week suggests one answer: greed. Specifically, the greed of psychologists who hoped to receive, and in some cases did receive, financial benefits in exchange for providing the Pentagon with intellectual and moral cover for its torture of detainees.

The American Psychological Association, roughly the equivalent of the American Medical Association for psychologists, played a crucial, long-hidden role in the story of American torture. James Elmer Mitchell, who created the C.I.A.’s torture program with Bruce Jessen, was a member of the A.P.A. Psychologists sold the C.I.A. and the Pentagon on a menu of aggressive interrogation techniques presented as scientifically proven to be effective; in reality, they were based on Communist methods designed not to find the truth but to produce false confessions that could be used for propaganda purposes.

When information about psychologists assisting in coercive interrogations began to trickle out in 2004, the A.P.A. did not condemn the psychologists involved. Instead, the A.P.A. defended them, thereby applying a sheen of respectability to coercive interrogations. The new, 542-page report—named after David Hoffman, the former prosecutor who oversaw the investigation—found that the A.P.A. task force that made some of these critical ethical decisions was influenced by behind-the-scenes collusion with the Defense Department.

Indeed, this was a uniquely American scandal—one with careerism and profiteering at its heart, and real science out the window. But a close reading of the 542-page report raises another troubling possibility: were it not for the immediate and future profits to be made by psychologists looking for any angle for self-advancement, the torture of detainees may have never happened at all.

As well, had the defense department, ever sensitive about public opinion, faced unanimous opposition from all the medical and mental health professional societies, it may well have been forced to reconsider its interrogation methods early on.

This began, for the most part, in 2005, when the executive board of A.P.A. convened the Presidential Task Force on Psychological Ethics and National Security to determine whether the A.P.A. ethics code adequately addressed a relatively new phenomenon in the war on terror: psychologists who were in the room during coercive interrogations, and helping to extract intelligence. The PENS task force deliberations led to a change in the organization’s ethics code, which clarified that psychologists could be present, so long as they saw their role as to help keep the interrogations safe, legal, ethical and effective.

It was a loophole big enough to drive a waterboard through.

In 2006, a number of the psychologists who sat on the task force, and disagreed with its conclusions, came to see me, alleging that the process had been manipulated, the task force itself had been packed with military psychologists and its conclusion essentially pre-ordained. The task force records they gave me held no overt evidence of collusion. However, my investigation ultimately led me to find that it was two psychologists on contract to the C.I.A., Mitchell and Jessen, who had actually designed the C.I.A.’s coercive interrogation regimen, by reversing the tactics used in a military training course, Survival, Evasion, Resistance, Escape (SERE), that is used to train troops how to resist interrogations.