As the magnetic properties of haemoglobin changes whether it is carrying blood or not, it is possible to detect which brain cells are using oxygenated blood, and therefore processing information. When a person is lying, it is thought that more areas of the brain are active than usual as they grapple to put together a false story.
However, a major assumption of this principle is that every person’s brains works identically. People’s physiology is extremely varied, meaning huge samples are needed in order to reveal any sort of correlations and results. Any researcher worth their salt will immediately be sceptical at the thought of obtaining results from just one subject. In cognitive neuroscience studies a minimal sample of 30-40 people are usually scanned in order to get an average showing results. Another concern of researchers worldwide is whether the lab based experiments are true representation of the real world. If you’ve ever been inside a MRI scanner, you’ll know it’s not entirely comfortable; it’s not the same as sitting in a room having a bit of a chinwag with someone and telling a bit of a fib!
Last year, fMRI data was used for the first time in an American court room, although not as a lie detector. The defence in a murder trial tried to use fMRI evidence to persuade the jury that their client had a mental illness. It didn’t, and the defendant was given the death penalty. Attempts have been made to use fMRI ‘lie detector’ data in court, but so far judges have thrown it out before the jury has even seen it. Despite this, many are still convinced that one day fMRI lie detecting scans will become a reality. |