Washington: A study claims that there are people who are good in hiding information and can easily fool the brain imaging technique called fMRI. They can easily get away by using mental countermeasures which reduces the results of the test.
The study was published in the journal, ‘Human Brain Mapping’
The work was led by a group of researchers in Plymouth, in collaboration with the University of Padova, Italy.
This research is the first to explore the effects of mental countermeasures on brain activity in functional magnetic resonance imaging (fMRI) and it showed that when people used the countermeasures, the test proved to be 20 per cent less accurate.
How do concealed information tests work?
Concealed information tests work because a person who is hiding something will ‘give away’ what they are concealing when faced with it in a list. For example, if a thief has stolen a diamond ring, the ring will be more striking to the thief than similar control items such as necklaces and bracelets and the thief will show physiological signs like sweating, panicking that will reveal the guilt of the thief.
However, these tests are based on physiological signs and are easy to beat as perpetrators can artificially alter them when seeing a control item. To overcome this problem, researchers moved to methods that look directly at brain activation using fMRI.
An fMRI machine tracks blood flow to activated brain areas. The assumption in concealed information detection is that the brain will show signs of recognition when presented with the concealed items while exerting extra effort to conceal signs of such recognition, and so the brain regions that do more work will get more blood. Such regions light up in scans, and they are primarily involved in directing attention and in decision making.
What did the study show?
In the new study, participants were asked to conceal information about a ‘secret’ digit they saw inside an envelope.
Researchers taught 20 participants with two mental countermeasures. 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.
The results showed that these countermeasures lowered the accuracy of the test by about 20 per cent because it was more difficult for fMRI to find any differences in brain activity. Thus, participants were more likely to be able to hide their concealed information item when using mental countermeasures.
The research team concluded that in order to improve the robustness of the test, future work needed to identify a way of detecting mental countermeasures, and potentially look at conducting whole-brain analyses, rather than just examining regions of interest.
One of the lead authors said, “fMRI tests are not currently used by law enforcement in the same way as polygraph tests, but they have been considered for scientific and criminal use as a way of detecting when someone is concealing information. This study shows that the process can be manipulated if someone associates meaningful memories to the control items, or focuses on the aesthetics, rather than the memory, of the item they’re trying to hide.”
Adding, he went on to say, “None of our participants was seasoned liars or criminals, they were just everyday people, so before this test can even be considered for forensic use, there must be further studies carried out to help identify when someone is using mental countermeasures.”