Saturday, February 04, 2006

More Lies... Damn Lies...

Well, there's a lengthy new article on neuro-lie detection in the New York Times Magazine, which quotes the aforementioned Dr. Langleben (among others):

Looking for the Lie
By ROBIN MARANTZ HENIG

Liars always look to the left, several friends say; liars always cover their mouths, says a man sitting next to me on a plane. Beliefs about how lying looks are plentiful and often contradictory: depending on whom you choose to believe, liars can be detected because they fidget a lot, hold very still, cross their legs, cross their arms, look up, look down, make eye contact or fail to make eye contact. Freud thought anyone could spot deception by paying close enough attention, since the liar, he wrote, "chatters with his finger-tips; betrayal oozes out of him at every pore." Nietzsche wrote that "the mouth may lie, but the face it makes nonetheless tells the truth."


Still quite the timely topic, so The Neurocritic feels obligated to weigh in here. This quote jumped out after a cursory glance:

Langleben performed his card experiment again in 2003, with a few refinements, including giving his subjects the choice of two cards to lie about and whether to lie at all. This second study found activation in some of the same regions as the first, establishing a pattern of deception-related activity in particular parts of the cortex: one in the front, two on the sides and two in the back. The finding in the back, the parietal cortex, intrigued Langleben.

"At first I thought the parietal finding was a fluke," he said. The parietal cortex is usually activated during arousal of various kinds. It is also involved in the manifestation of thoughts as physical changes, like goose bumps that erupt when you're afraid, or sweating that increases when you lie. The connection to sweating interested Langleben, since sweating is also one of the polygraph's hallmark measurements. He looked at existing studies of this response, and in all of them he found activity that could be traced back to the parietal lobe. Until Langleben's observation of its connection to brain changes, the sweat response (which the polygraph measures with sensors on the palm or fingertips) had been thought to be a purely "downstream" change, a secondary effect caused not by the lie itself but by the consequences of lying: guilt, anxiety, fear or the excess positive emotion one researcher calls "duping delight." But Langleben's findings indicated that it might have a corollary "upstream," in the central nervous system. This meant that at least one polygraph measurement might have a signature right at the source of the lie, the brain itself.

Yeah, right, like the parietal cortex is the "seat of arousal." This is one of the most annoying problems about neuroimaging... researchers will say, after all the results are analyzed, "well of course we thought the parietal lobe would be associated with sweating and other autonomic measures!" when, in fact, that is not what they expected at all. But maybe he means association areas in the anterior parietal cortex?

On the other hand, increased activity in the anterior cingulate cortex (ACC) has been associated with arousal and autonomic activation, according to the work of Tomas Paus, Hugo Critchley, and others. It would be logical that the ACC would respond when a person is lying, and one need not postulate that it's for cognitive reasons (e.g., choosing between conflicting responses, as mentioned below):

Brain mappers are just beginning to figure out how different parts of the brain function. The function of one region found to be activated in the five-of-clubs experiment, the anterior cingulate cortex, is still the subject of some debate; it is thought, among other things, to help a person choose between two conflicting responses, which makes it a logical place to look for a signature of deception. This region is also activated during the Stroop task, in which a series of words are written in different colors and the subject must respond with what color the ink is, disregarding the word itself. This is harder than it sounds, at least when the written word is a color word that is different from the ink it is written in. If the word "red" is written in blue, for instance, a lot of people say "red" instead of "blue." Telling a spontaneous lie is similar to the Stroop task in that it involves holding two things in mind simultaneously — in this case, the truth and the lie — and making a choice about which one to apply.

In fact, here's a study that observed a correlation between mean arterial pressure during the Stroop task and greater BOLD activation in the ACC, among other regions (insula, thalamus, periaqueductal gray):

Gianaros PJ, Derbyshire SW, May JC, Siegle GJ, Gamalo MA, Jennings JR.
Anterior cingulate activity correlates with blood pressure during stress.
Psychophysiology. 2005 Nov;42(6):627-35.

Gianaros et al. concluded that their results "support the hypothesis that the anterior cingulate cortex regulates blood pressure reactions to behavioral stressors in humans."

SO is fMRI an improvement over the polygraph, you ask? Stay tuned...

Subscribe to Post Comments [Atom]

0 Comments:

Post a Comment

Links to this post:

Create a Link

<< Home

eXTReMe Tracker