I'm lying.

That sentence is a variation of what's known as the "liar paradox," a philosophical conundrum: If the sentence is true, then the assertion is false (because I'm not lying); if the sentence is false, then the assertion is true. Therefore, the sentence is both true and false at the same time.

Technology is used to help find the truth (think business intelligence), sometimes literally. Researchers at Cornell University are developing software they say will be able to tell when a person is lying in e-mail or IM (see "Lie-Detection Software Could Scan E-Mail, Text Messages"). For the past three years, Jeff Hancock, a professor at Cornell, has been studying indicators in electronic communications about when a person is lying. Some giveaways: passive voice, lengthy missives, and the use of personal pronouns other than I.

Journalists search for the truth, mostly. They do it through the process of elimination: That's a lie, that's a lie--so that must be the truth. Technology used to determine the truth often takes the same form, as with the Cornell software. Or the polygraph machine, popularly known as the lie detector. A new book called The Lie Detectors: The History Of An American Obsession (Free Press, 2007) chronicles the invention, refinement, and acceptance--in police work and the popular imagination--of the "cardio-pneumo-psychograph," a simple, but intimidating, blood-pressure and respiration measuring machine.

It's a rollicking tale of pragmatism, self-aggrandizement, and, well, stretching the truth. Lie-detector data was ruled early on too unreliable to serve as evidence in a courtroom, but the lie detector is still widely used in the United States as an interrogation device.

It's interesting to note that the inventor of the lie detector, John Larson, ended up referring to it as "a Frankenstein's monster" because of its potential for misuse, a deliberately apt metaphor for technology run amok. I've never taken a lie-detector test. Frankly, I'm afraid of it.

The test administrator sits off to my right side, just on the edge of my peripheral vision, monitoring the machine. Electrodes are attached to my chest and the blood pressure cuff is wrapped around my arm.

TESTER: Are you comfortable?

ME: Yes. Wait--that's a lie. Does that count against me?

TESTER: Is your name John Soat?

ME: I think so. I'm pretty sure. Yes, it is.

TESTER: Is technology a good thing?

ME: Is it just the two of us talking here?

TESTER: I'm asking the questions.

ME: I write for a technology magazine. I'm not allowed to say technology isn't a good thing.

TESTER: Please answer yes or a no.

ME: Yes, technology is a good thing. Mostly.

TESTER: Will technology eliminate privacy?

ME: I don't know. Am I allowed to say that? It depends on your definition of privacy, I guess.

TESTER: That's enough. We're not going to learn anything here.

Distinguishing a lie from the truth isn't easy. It's often a subjective exercise, one that can be manipulated easily. And lies can serve a purpose. Anyway, I'm not sure I always want to know when someone isn't telling me the truth. Then again, I might be lying--to myself.

Don't lie to me--I know you have an industry tip, so send it to [email protected], or call me at 516-562-5326.

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