Is Foolproof Lie Detection in the Cards?

Researchers seeking more reliable lie detection methods are experimenting with brain scan technologies.

Illustration by Jameson Simpson

Illustration by Jameson Simpson

Researchers seeking more reliable lie detection methods are experimenting with brain scan technologies such as functional magnetic resonance imaging (fMRI). First they must create a scenario in which study subjects will lie predictably. Then they observe blood flow within subjects' brains as they alternately fib and tell the truth. The result: Scientists are starting to identify the specific areas in the brain where lies are formed.

1. What You're Told

You're shown three envelopes and told each contains a different card and $20. You choose one, open it, and are told if you can hide your card from the machine, you'll keep the $20.

2. The Machine

In the fMRI scanner, a series of cards flash on a screen, each accompanied by a question. You're instructed to tell the truth whenever possible but not to reveal your card.

3. The Test

Over a period of 22 minutes in the fMRI machine, you are presented with 88 cards, each with an associated question. Here are some examples:

2 of hearts
"Do you have this card?" You answer no. The purpose of this card is to show the researchers the parts of your brain that are activated when you're telling the truth.

5 of clubs
"Do you have this card?" You answer no. The purpose of this card is to show the
researchers the different parts of your brain that are activated when you're lying.

4 of diamonds
"Do you have this card? You answer no. The purpose of this card-plus 10 other cards that will be shown to you for the same reason-is to provide you with variety.

10 of spades
"Is this the 10 of spades?" You answer yes. The purpose of this card is to throw in a different kind of question, to make sure you keep paying attention.

4. What's Going On

All three envelopes contained the 5 of clubs, since the researchers had to know when you were lying and being truthful. You were given the choice so you'd think you could lie plausibly.

5. The Lie Zone

This fMRI image shows brain areas that receive more blood flow when a person is lying. The anterior cingulate cortex (A) manages conflicting impulses; the left lateral prefrontal cortex (B) is involved in response inhibition.