fMRI determines lies better than a polygraph

When it comes to lying, the brain can make us stronger than sweaty palms or sudden heartbeat jumps. This is the conclusion reached by scientists from the Perelman School of Medicine at the University of Pennsylvania . The results of their research showed that scanning the brain with a functional MRI or classical magnetic resonance imaging will be much more effective in diagnosing a lie than a traditional polygraph test.

When a person lies, those decision-making sites are activated in his brain. Experts can see these foci when scanning fMRI. Laboratory studies have shown that MRI can reveal deception with an accuracy of 90%. Depending on the study, the accuracy of the polygraph is from randomness up to full 100%.
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This study is the first of its kind when the same people were tested using two methods. This approach adds scientific information to longstanding disputes about the effectiveness of a tomogram as a lie detector and gives impetus for further study of its potential and applications in real life. For example, for evidence in criminal proceedings.

“The measurements of the polygraph reflect the activity of the peripheral nervous system, which boils down to just a few parameters. MRI gives us the opportunity to see thousands of different parts of the brain in high resolution. Although no type of activity is a 100% true indicator of lies, it seems to us that the response of the brain may be the most accurate marker, ”says study lead author Daniel Langleben.

Specialists from the Faculty of Psychiatry, Biostatistics and Epidemiology found that neurology experts without experience in lie detection, using tomography data, have a 24% chance of detecting deception by 24% higher than professional polygraph examiners.

During the experiment, volunteers passed a standardized information hiding test, which is used in the FBI. It was designed specifically for polygraph examiners to demonstrate the effectiveness of their methods before the subject undergoes an actual lie detector test. During the test, the person is asked questions, some of which the experts already have the answers. Thus, they seek out the answers that are accompanied by jumps in physiological activity.

To compare the two technologies, 28 participants secretly wrote down a number from 3 to 8 on a piece of paper, and then answered questions. Each person had to go through both detectors in a different order with a certain time difference. During both sessions, they were instructed by experts to say “no” to questions about all the numbers, which makes one of the six answers false. The results were then evaluated by three polygraph examiners and three neuroimaging experts. At first they acted separately, and then the results were combined to find out who coped better.

In one example, fMRI clearly showed brain activity at the moment when the participant who wrote 7 was lying. Experts who made wrong conclusions from the polygram data interpreted number 6 as false. The lie detector reacted to figure 6 after the participant was asked the same question several times in a row, suggesting that he was lying. Both methods are still imperfect; however, in general, fMRI experts had a 24% higher chance to detect the lies of the experiment participants.

In addition to comparing accuracy, the authors of the study made an important observation. In 17 cases, when two out of three experts in each group came together, the total accuracy of their assessments was 100%. Such high accuracy of positive definitions can be especially important for criminal proceedings in the United States and the United Kingdom, where the prevention of false convictions prevails over the capture of criminals.

Despite the obvious success, the researchers warn that it is too early to talk about the immaculate accuracy of the combined methodology. Yes, both of these tools can complement each other if used consistently. However, their work did not involve the combined use of both methods. The observation, which was established, did not fit into the framework of the experiment and turned out to be an accident. It requires more careful study before certain conclusions are drawn.

The first prototype of the polygraph was assembled by policeman John Larson in 1921. Invented more than half a century ago, the technology captures indirect signs of excitement: heart rate, sweating, pressure. The work of the polygraph is based on the assumption that sharp jumps of these indicators up or down indicate a lie. Its development became popular and was widely used in the investigation of crimes. However, its effectiveness was criticized even then. Over time, Larson himself was disappointed in his brainchild. Shortly before his death, he said that this device - "the monster of Frankenstein, with whom I fought for over 40 years." His statement was not unreasonable.

Defenders of the polygraph declare its 90% accuracy, but the data confirming this fact is not enough. Today, the polygraph remains the only physiological lie detector that is widely used throughout the world. The results of such examination are accepted in most US courts. In addition, all employees of secret organizations have been tested for polygraphs for almost 30 years before being hired. The polygraph is widely used for government checks and access to classified information. However, verification by a detector is not considered 100% effective. But if, after all, a functional MRI in the near future will be used together with the usual lie detector, the probability of obtaining reliable information will be maximal. The combination of these tools will be a good assistant in the work of forensic experts.

Scientific work published in The Journal of Clinical Psychiatry
DOI: 10.4088 / JCP.15m09785