The lie detector has become a common trope in pop culture, popping up in spy films, police tv show dramas, and even in the occasional rom-com; think Meet the Fockers. When first introduced in the early 20th century it was dubbed the "mechanical instrument of the future" with the alleged promise of replacing jury deliberations and conventional police interrogations. However, most modern scientists would agree that is far from the truth.
Though you are probably already well aware of the polygraph, the term "lie detector" in our modern era is a broad term also taking into account software that analyzes the word choice and variation a subject uses when recounting an event, a Certified Voice Stress Analysis, and today's focus, an fMRI brain scan.
Out of these choices of lie detectors, the fMRI is much harder for a subject to trick, yet recently scientists from the University of Plymouth in collaboration with the University of Padova have recently discovered that the fMRI can be beaten by the use of two particular mental countermeasures.
In the research published in the Journal of Human Brain Mapping, the team of scientists explored the effects of mental countermeasures on brain activity in functional magnetic resonance imaging (fMRI), showing that when these countermeasures were used the tests were 20% less accurate.
Beating the Test
The study centers around concealed information tests. If a person is hiding something they tend to "give away" what they are concealing when faced with it on a list. Perhaps one day you stole a piece of cake from your roommate's fridge.
You most likely will not respond to other shown food items like a sandwich or chicken wing. But, when shown a picture of that piece of cake that you enjoyed the previous night, you will most likely show physiological signs that reveal your guilt.
However, these same physiological signs are easy to beat and control if you are self-aware of them, hence why researchers opted for using an fMRI brain scan in their concealed information tests. The fMRI machine tracks blood flow of activated brain areas.
Going back to the cake example, if you were shown that delicious piece of cake, there is a good chance that your brain will light up even if you are attempting to lie or conceal any physiological signs. And, this is where things get interesting.
Lead by Drs Chun-Wei Hsu and Giorgio Ganis, scientists asked participants to conceal information about a secret digit that they saw inside an envelope. Researchers also taught participants two mental countermeasures.
As mentioned in the study, "the first was to associate meaningful memories to the control items, making them more significant. The second was to focus on the superficial aspects of the item they were trying to conceal, rather than on the experience of familiarity it evokes, in order to make it less significant."
By using these two countermeasures participants were able to lower the accuracy of the test, concealing their information, even when using an fMRI to find any differences in brain activity. If anything the study highlights again, how these tests can be manipulated, confirming that they are not that reliable.
Keep this in mind, if you ever have to pass an fMRI lie detector test.