Can an MRI machine also act as a lie detector?

How MRI Lie Detectors Work

An MRI image of an overactive amygdala,
An MRI image of an overactive amygdala,
Photo courtesy National Library of Medicine/National Institutes of Health

An MRI uses a magnetic band as a scanner to peer through tissue and bone to see within the human body. To use an MRI as a lie detector, however, an fMRI -- functional MRI -- must be used. FMRIs are connected to specialized software able to not only display, but also analyze the images the MRI produces.

Within these pictures, different parts of the body are shown highlighted in different colors. The more active the system, the brighter the area. For use in brain scans, the fMRI analyzes blood flow to specific regions of the brain. Neurons in the brain need blood to operate, and a sudden demand for blood suggests activation of a region.

Imagine being in an MRI while you ride a bike. If you decide to turn left, the MRI image could conceivably show the different regions of the brain that are involved in the process of turning left. One part tells your musculoskeletal system to shift your balance, another region tells the eyes to look both ways for oncoming traffic, and another maintains the pedaling motion produced by your legs.

By studying the images, researchers could map the systematic procedure your brain went through to produce the left turn. What's more, neurologists are now finding they can see the process by which you made the decision to turn left, rather than turning right or staying straight.

It's through analysis of these regions and knowledge of what function for which each region is responsible that has led to the possibility that MRIs can predict truth-telling.

The idea for the use of MRIs as lie detectors came from some very innocent research. To investigate whether children diagnosed with attention deficit disorder (ADD) were unable to tell lies, University of Pennsylvania psychiatrist Daniel Langleben conducted MRI scans on young patients with the disorder. Langleben discovered that deception activates regions in the pre-frontal cortex. These were perhaps the first snapshots ever taken of lies.

Langleben's findings have been supported by other researchers. At Temple University, Scott Faro conducted a study whereby he asked some volunteers to lie and others to tell the truth while in an MRI. He found that more regions of the brain -- including those same pre-frontal regions Langleben identified -- are used during deception than in truth-telling.

And at the Max Planck Institute in Germany, John-Dylan Haynes conducted an experiment in which he asked students to decide whether they would add or subtract two numbers before they saw them. Haynes fed a portion of the 250 tests conducted for each student into a computer algorithm, which then searched for patterns in the images. After excluding the sample tests, the computer was accurately able to predict whether a student would add or subtract -- based solely on the images of the student's brain -- 71 percent of the time.

The results of these experiments show that much of what we understand as our decision-making process -- including the decision to lie -- occurs at the front of our brains. What's more, we can now see these processes. In effect, through MRIs, we have reached the point where we can read a person's mind.

The field of using MRIs as lie detectors is still in its infancy. But with the amount of attention being paid to the research -- as well as the funding being poured into it -- there's little doubt that it will advance by leaps and bounds over the coming decades. The question is, should we use this technology? Read the next page to explore the pros and cons of reading people's minds.