Thursday, May 14, 2009

Detecting Liars

Back in my former career, it was often said that it must have really sucked to be one of my kids when it came to trying to tell a lie. I spent 15 years as a fraud investigator, and had attended both basic and advance interview and interrogation schools, so I could spot an untruth walking down 5th Avenue.

Bruce Schneier, writing in his Schneier on Security blog, weighs in on comments made by psychologist Kevin Colwell, from Southern Connecticut State University, who has advised parents, police departments, Pentagon flunkies, and scores of others on lie detecting based on the amount of detail presented by the person in question.

In several studies, Dr. Colwell and Dr. Hiscock-Anisman have reported one consistent difference: People telling the truth tend to add 20 to 30 percent more external detail than do those who are lying. "This is how memory works, by association," Dr. Hiscock-Anisman said. "If you're telling the truth, this mental reinstatement of contexts triggers more and more external details."

There's a measure of truth (!) to this approach, but it's just one piece to an enormously complex puzzle. Does the speaker use significant detail in non-threatening conversations but resorts to a lack of detail when pressed on the topic in question? What about their non-verbal communication mechanisms, mannerisms, posture, and so on?

Here's an example - having been trained as an interrogator, if someone asks me if I know what time it is, my answer is either "yes" or "no", and that's it. 98% of the population will respond with, "Yes, it's 5:15" because that's the customary response. In an interview / interrogation scenario, I want to give up as little information as possible, while the interrogator wants me to spill my guts, metaphorically (and if you're Dick Cheney, literally) speaking.

Does this mean I'm being dishonest in my responses? Not at all. When did it become my job to answer the interrogator in the manner that he or she wants? My responsibility is to me, and anything that puts that at risk is a no-go.

If you think I've committed a crime, charge me. If you don't have enough to charge me, don't expect me to give you the evidence you need. Talk to the hand, buddy.

Schneier on Security: Detecting Liars by Content

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