Pretend to be their friends.

A study published this year by Australia, Indonesia, and Norway who had handled 30 international terrorism suspects, including potential members of the Sri Lankan extremist group Tamil Tigers and the Norwegian-based Islamist group Ansar al Ismal. Delahunty asked the interrogators what strategies they used to gain information and what the outcomes of each interrogation session were.

The winning technique, as BPS Research Digest notes, was immediately clear:

Disclosure was 14 times more likely to occur early in an interrogation when a rapport-building approach was used. Confessions were four times more likely when interrogators struck a neutral and respectful stance. Rates of detainee disclosure were also higher when they were interrogated in comfortable physical settings.

This isn't just theoretical, either. One former U.S. Army interrogator told PRI this week that he was able to break through to an Iraqi insurgent over a shared love of watching the TV show 24 on bootleg DVDs.

"He acknowledged that he was a big fan of Jack Bauer," he told PRI. "We made a connection there that ultimately resulted in him recanting a bunch of information that he had said in the past and actually giving us the accurate information because we had made that connection."

Delahunty notes in the study that even though rapport-building strategies, which included things like humor and expressing concern, were recognized as more effective, interrogators were still more likely to use hardball accusatory strategies when dealing with "high-value" detainees, perhaps because the nature of their crimes were considered too horrendous for buddy-buddy interviewing.

In another study highlighted by BPS, regular people were found to be more supportive of torture if they were told the suspect was a terrorist—but not because they thought the suspect had more information. Their support for torture, in other words, was rooted on a desire for payback, not intelligence.

Torture can either be viewed as a punishment or as a way to gain life-saving intelligence. International conventions prohibit the former. Psychology studies suggest it's ineffective at the latter. Which brings us, once again, back to the question: Why do it?

* This post originally stated the wrong date for Napoleon's letter. We regret the error.