The body doesn’t lie. At worst, even with the most accomplished, natural-born liar, the body is neutral. Yes, it would be nice if we all broke out in a sweat or blushed red when we told lies, but that doesn’t happen often. Most people who have these extreme bodily reactions recognize their hopeless situation and swear off lying altogether. Other, subtler clues to deception can be detected under the right circumstances. When a person is stressed by the sudden fear or excitement of telling a lie, his autonomic nervous system kicks in. It pushes adrenalin into the blood stream, and this increases the heart rate and blood pressure, quickens breathing, and induces sweating. You can think of it as a primitive part of the brain getting the body ready to fight—or to make a run for it. These are also the body’s reactions that the polygraph (the “lie detector”) is set to measure. There are other effects of stress that don’t get much mention: the mouth is dry, the stomach contracts, the nipples erect, the penis shrinks and the testicles are drawn up (nature has provided a special muscle for this purpose). Unfortunately, we rarely have occasion to question our loved ones when they’re stark naked and hooked up to a blood-pressure cuff. Few of these measures are practicable for the amateur interrogator. It’s possible, if you listen carefully, especially if someone’s prone to asthma, that you may hear a change in breathing. You may hear the snap of the tongue in a dry mouth.  In my experience, the effects of emotional stress are best observed in the muscles. Adrenalin released under stress has a direct effect on muscles: When they’re anxious, people tremble. Occasionally I interview subjects with a tremor in their hands that is so marked that I can see it when they’re sitting in front of me; but this is in cases of extreme fear—someone who’s lying, for example, about a major crime he’s committed. Under more ordinary circumstances, the trembling of anxiety isn’t easily visible to the naked eye.
The polygraph, essentially, is an electronic device for amplifying small bodily changes. For example, it picks up minute changes in the electrical conductivity of the skin that are caused by changes in sweating, feeds the electrical signal through an amplifier, and then prints the result out on scrolling paper. You don’t have a polygraph at home, but you can find ways to amplify the small tremor in the hands of the nervous subject so that they can be made visible.  We do this by applying leverage. The closer the subject keeps his hands to his body, the easier it is to steady them, and the more he’s able to disguise a shake. (Is this the reason he has his hands in his pockets?) We want to increase the leverage at the end of the subject’s hand by getting him to perform an action where a small movement out of alignment will become obvious.
First we want him reaching out his hand to the arm’s fullest extent, such as passing a cup of coffee. Or a martini glass. We want to extend it even further and have him hold something heavy to increase the leverage: Better yet, make that a coffee mug. Then we want whatever he’s holding at the end of his hand to make small movements obvious: the coffee mug should be full to the brim so that the slightest lurch will show a spill. Reaching with a full spoon of sugar embodies the same principle. Since you’re not going to be able to have him stand with a coffee mug at the end of this outstretched arm for longer than a moment, you have to time this movement to your crucial questioning (next month, the Liar Tip-Off will feature the art of the ambush question). Make him stretch out both hands, if you can. This takes a certain amount of manipulation. So, set him up with a brimming martini glass in each hand, and fire away with the questions!
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