Truth Serum

Lying generates unique brain activity that can be measured by
functional magnetic resonance imaging (fMRIs), brain scans that could
someday morph into a forensic tool far more potent than the flawed
polygraph test.

Researchers gave 18 subjects a playing card, then offered them
money to lie to a computer about the card while undergoing an fMRI. When
subjects lied, the scans revealed increased activity in several regions
of the brain, including the anterior cingulate gyrus, which is implicated
in conflict monitoring, attention and response inhibition. Head
researcher Daniel Langleben, M.D., a professor of psychiatry at the
University of Pennsylvania, says this confirms that the brain's "default"
response is to tell the truth. "No area of the brain works harder to tell
the truth than to lie" says Langleben.

Forensic experts are hopeful because fMRIs measure complex mental
processes, while polygraph tests pick up skin and blood pressure changes
that can be misleading. Langleben says the next step to ready brain scans
for forensic use is to monitor spontaneous acts of deception. Langleben
modeled his study on classical deception research, in which subjects are
instructed to lie. The study was presented at the Society for
Neuroscience annual meeting.