It may be difficult to tell if someone is lying from the outside. But a new study is the latest to find that a brain scan may be the ticket to calling someone's bluff.
Researchers from Baylor College of Medicine and California Institute of Technology used functional magnetic resonance imaging, or fMRI, to scan the brain activity of 76 study participants while they played a bargaining game. In the game, a buyer and seller bargained with each other for the best price. Only the buyer knew the real price of the item.
The study authors found that the buyers who bluffed showed more activity in the brain regions that contribute to complex decision-making, maintaining goals, and understanding other people's beliefs.
"Although it's controversial, my interpretation is that humans have a natural instinct toward honesty," said Dr. Colin Camerer, the Robert Kirby professor of Behavioral Economics at California Institute of Technology, and the co-author of the study. "To be actively dishonest requires extra thinking, so the brain would be working harder."
The findings, published in the Proceedings of the National Academy of Sciences, suggest that this brain activity may help differentiate between honest individuals and those who attempt to manipulate their social image in another person's mind. In the future, the authors said these scans could help diagnose mental disorders or contribute to finding the truth in the courtroom.
But, is all deception the same? Right now, researchers can't be sure if bluffing in a poker game appears the same way in a brain scan as would lying under oath about a criminal offense.
For several years, doctors, lawyers and police have researched the use of brain scans to replace or supplement polygraph tests.
"If an individual is guilty, the polygraph has an 85 to 90 percent accuracy rate," said Dr. Scott Faro, a professor of radiology and director of the Functional Brain Imaging Center and Clinical MRI at Temple University School of Medicine. Faro has been involved with similar research on intentional deception for several years.
Doctors say that hopefully at some point brain scans will become more precise than lie detectors in getting at the truth, but it probably won't happen any time soon.
"We need to create a technique that is accurate and reproducible to be able to use it in a larger setting," said Faro. "I think the MRI might not be the only test in the future, but an MRI and other measurements together in combination will most likely increase the accuracy of lie detection in the future."
The study is only the latest to explore how an MRI might be used to detect how honesty and deception affect the brain.
Dr. Daniel Langleben, associate professor of Psychiatry at the Philadelphia Veterans Administration Medical Center, is at least one researcher who said he wasn't surprised by the results of the new study, or that the latest work didn't seem to recognize past research.
"I was surprised to see that this paper didn't reference 10 years of work on this topic," said Langleben, who has published numerous papers on the use of fMRI as a way to detect intentional deception. "Maybe this is a new development on an existing topic, but it seems to be consistent with a large body of literature that has been developed in the last 10 years on intentional deception, and they have replicated it in some sort of bargaining game."