When we think of lie detectors, most of us imagine polygraphs that measure physiological changes like sweating, blood pressure, respiration, and heart rate, which can be associated with deception-induced anxiety.
Now, rather than focusing on the potential end results of lying, Temple University scientists Scott Faro and Feroze Mohamed are developing a way to detect deception by looking directly at people's brain activity using MRI brain scanners.
"We are going to the source; we are going to the region of the brain that is actually formulating a response," says Mohamed, the MRI physicist on the team.
In this preliminary study, the researchers wanted to see whether brain scans can even pick up a significant difference between brain activity during lying versus when telling the truth. The researchers had 6 of 11 volunteers fire a gun, then lie and say they didn't. The other five could truthfully say they didn't fire the gun. All the volunteers were then given functional MRI tests during which they denied having fired the gun.
As they reported in the journal Radiology, the brain scans revealed unique areas that only lit up during lying. However, the researchers point out that there isn't one telltale spot in the brain that can automatically indicate a lie. "There really is no one lying center," Faro says. "There are multiple areas in the brain that activate because there are a lot of processes that have to take place."
Instead, Faro and Mohamed say that developing this method into a viable lie-detection system will depend on discovering complex patterns of brain behavior linked to lying. One of the most important of these is that the brain has to work much harder to lie than to tell the truth.
"In the group that lied there were two times the number of areas throughout the brain that showed activation compared with the group that was telling the truth," Faro says. That's because to lie, you have to actively suppress memories that are triggered by the question, which takes more effort than simply asserting the truth, he says.
Faro and Mohamed say a lot more research is needed, but they believe this method could one day be more accurate than a polygraph. Although they're not yet certain whether it will be possible to trick the MRI, they say it's harder to change what your brain is doing than to suppress your nervous responses.
"I think it will be very, very hard for somebody to cheat," says Mohamed.