DAVID POGUE: Jennifer Vendemia and her team at the University of South Carolina are trying to identify deception at its very source.

All of a sudden, I'm a melon.

And today, the brain going under her microscope is mine.

JENNIFER VENDEMIA: So, what we're going to do is we're going to get a picture of what David's brain looks like when he lies and when he tells the truth.

DAVID POGUE: That picture will come from this net of 128 electrodes.

JENNIFER VENDEMIA: This is the torture part.

DAVID POGUE: Each one picks up tiny electrical impulses coming from my brain cells.

Brain cells communicate with one another by firing off tiny chemical and electrical signals in rhythmic pulses. When enough brain cells fire at once, the electrodes can pick up their pulses in the form of brain waves.

Is this an eBay hair salon purchase here?

To get the best readout, Vendemia must carefully map the electrodes by taking a picture of my head, as I sit inside this weird contraption.

It's like, "Captain, I sense a disturbance in the tri delta vector."

JENNIFER VENDEMIA: Go ahead and hold very still for me.

DAVID POGUE: Finally, I'm ready to do some lying.

Sitting as still as possible, I read statements on a computer screen. Then I have to press a button, declaring the statement either true or false.

JENNIFER VENDEMIA: During the study, you're going to see sentences presented in the color red and sentences presented in the color blue. When the sentence is red, I want you to lie, and when it's blue, I want you to tell the truth.

DAVID POGUE: As I ponder each question and figure out how I'm going to respond, Vendemia scours my brain waves in this color-coded, circular map.

JENNIFER VENDEMIA: You would think that, when we're looking for deception, we're trying to find one moment of deception, one moment in the brain where the lie happens. But really, we build the lie over time.

DAVID POGUE: In the split second my brain is deciding whether or not to lie, Vendemia hunts for a particular kind of brain wave, called the P300, that shows up as red blotches on her graph.

JENNIFER VENDEMIA: The P300 is the result of any decision-making process. When a task is really easy, every process that results in the P300, kind of, comes to closure all at once.

DAVID POGUE: The P300 brain wave fires when I make a clear and confident decision.

JENNIFER VENDEMIA: This is about 200 milliseconds before he responds to us. This picture on the right—the truth telling picture—all these red areas indicate that the process is done. In about 200 more milliseconds, he's going to tell us the truth.

DAVID POGUE: Whenever I decide to tell the truth, red blotches burst out across my brain map, even before I push the button to give my answer. But whenever I decide to lie, my brain seems to struggle a bit more. The different areas involved in the decision take a fraction of a second longer, and the red P300 often doesn't show up at all.

JENNIFER VENDEMIA: On the left, he still has more processing to do before he is going to be ready to lie. It takes longer to lie, because more processes are involved in deception.

It's just harder to tell a lie than to tell the truth.

DAVID POGUE: Vendemia sees the same distinctive patterns with her other subjects. She says she can tell when a brain is coming to a quick and easy decision to tell the truth…

JENNIFER VENDEMIA: On the right is truth.

DAVID POGUE: …and when it's working a little harder to lie.

JENNIFER VENDEMIA: On the left is lying.

DAVID POGUE: You got to the point where you could look at the data and, without seeing what the question was, know whether I was lying or not?

JENNIFER VENDEMIA: Yes.

DAVID POGUE: You got to that point?

JENNIFER VENDEMIA: Yes. Absolutely. In fact, we got to that point with about 85.3 percent accuracy for you.

DAVID POGUE: That's freaky.

This research is still very preliminary, and it hasn't been tested on psychopaths and others who may be able to fool traditional lie detection tests. Still, if lie detection is going to move forward, there's a good chance it will be in this direction, probing the mind in more profound ways and threatening the idea that our thoughts are exclusively our own.