Electroencephalogram Becoming the New Lie Detection Test
By Melanie Schmitt
Most individuals have heard of a polygraph lie detection test. They are used a lot in television shows such as CSI or Criminal Minds where detectives use a polygraph test to determine if the criminal actually committed the crime they were convicted for. A polygraph lie detection test examines a person’s autonomic nervous system which is the unconscious regulation of bodily functions, such as heart rate, breathing, and digestion. The people being tested with a polygraph test are usually asked a series of ‘Yes or No’ questions. Many people think this is a reliable way of learning the ‘truth’ about what someone did or is going to do. There has been evidence that shows polygraph tests are not the most reliable when it comes to detecting if someone is lying. People can make it seem like they are not lying when they really are, which then slips right through the polygraph test. Since polygraphs are so unreliable what is a more reliable source of lie detection? An electroencephalogram or an EEG. EEGs record brain activity of certain areas of the brain when certain items or events are recognized before we are even conscious that we recognize them.
When looking at an EEG test, there is a specific spot to look at on the brain which is called the P300 or P3 wave (located on the parietal lobe or the top back part of your head). The P300 spot is involved in decision making and recognition. There are event related potentials that go along with P300. these event related potentials represent brain activity in response to a stimulus or activity. Then a P300 event related potential is a positive deflection on an EEG around 300-800ms after being shown a stimulus (1). These positive deflections show up on an EEG scan quickly, which would then show if you recognize an image or if the image has any sort of connection to you.
Let’s say you were a part of an EEG experiment where you had to give experimenters a picture of your pet. The researcher would show you different pictures of other people’s pets on a screen and then your pet would randomly appear on the screen. The P300 wave on an EEG would spike showing that you recognized the animal. This spike would come way before you consciously realize that your pet is up on the screen. The person running the EEG would most likely be able to determine which pet is yours due to the spike on the EEG. When thinking about how an EEG can show that you recognize your pet, it would also be able to show if you were to recognize a weapon from a murder that you most likely committed. Thus, you would not be able to lie and say you have never seen that weapon before because your brain waves do not lie. Using an EEG would bring down the number of people who are wrongly thrown in prison for a crime they did not commit. If an EEG is able to prove that you are lying then it should be able to be used in courtrooms to determine if someone is guilty or not, right?
Sadly, it is not so simple. There are many reasons why EEGs cannot be used in courtrooms just yet. One reason is, there is a debate on if it is ethical to give someone an EEG test without their consent. I would say no because this is their brain and they have the right to not have their unconscious ‘thoughts’ up on a screen for a whole courtroom to look at and examine. Another question that could come up is, could a witness to the crime be convicted for the crime just because they saw it? The EEG would spike if they were shown the crime scene, but since they did not commit the crime the spike would not be as intense as the person who committed the crime. Using this type of technology could end up going terribly wrong, but it also could move courtrooms and evidence in the right direction. All in all, EEGs are really powerful tools that can be used to examine brain activity or consciousness in being able to determine if someone recognizes a weapon used in a crime that they may have committed.
References
(1) Rosenfeld, J.P. (2019). P300 in detecting concealed information and deception: A review. Psychophysiology. doi:10.1111/psyp.13362