When it comes to catching criminals, the outcome can be heavily reliant on details given by witnesses or suspects. Now, researchers from Northwestern University in Evanston, IL, claim that monitoring a particular brain wave of these individuals could aid criminal investigations, by confirming details they have seen or objects they recognize.
Study leader John B. Meixner and co-author J. Peter Rosenfeld publish their findings in the journal Psychological Science.
According to the researchers, past studies using electroencephalogram (EEG) recordings have indicated that when a person recognizes a meaningful item among a list of insignificant items – determined through what is called a concealed information test (CIT) – the P300 brain wave tends to get bigger.
But the team notes that the majority of these studies have been conducted in laboratories, meaning participants are not recalling details that they encounter in day-to-day life – like a witness of a crime would need to.
In this study, Meixner and Rosenfeld set out to achieve a more accurate CIT. They enrolled 24 college students, fitted their clothes with a small camera for 4 hours and asked them to go about about their normal daily activities.
“Much like a real crime, our participants made their own decisions and were exposed to all of the distracting information in the world,” says Meixner.
The researchers then reviewed the recordings. For half of the participants, the team created a list of “probe” items, which were items or events that a subject had encountered during the recording. They also created a list of “irrelevant” items that a subject had not come across.
For the remaining participants, the team made up a list of “probe” items that were drawn from other participants’ experiences, rather than items they had encountered themselves. The researchers explain that this was to mimic a real criminal investigation, in which witnesses or suspects who have knowledge of the crime are presented with the same details as those who may have no knowledge.
The participants underwent the CIT the day after their recordings. During this, they were presented with the list of probe and irrelevant items and their brain activity was recorded using EEG.
Results of the experiment revealed that P300 brain waves were only larger among participants who had actually encountered the items on their probe list. P300 brain waves did not increase for any irrelevant items shown to participants. Overall, the researchers say their findings indicate that the P300 brain wave is a “robust and reliable” marker of recognition.
Meixner says that possibly the most surprising finding in this study is the extent to which the brain wave peaked for very trivial activities – such as when a participant was shown the color of an umbrella they had used. He adds:
“This precision is exciting for the future because it indicates that relatively peripheral crime details, such as physical features of the crime scene, might be usable in a real-world CIT – though we still need to do much more work to learn about this.”
Meixner notes that some countries, such as Japan and Israel, already use CIT for criminal investigations, but that the US has likely dismissed the idea because it “may not meet the criteria to be admissible in a courtroom.”
“Our work may help move the P300-based CIT one step closer to admissibility by demonstrating the test’s validity and reliability in a more realistic context,” he adds.
In future research, the team plans to look at how recognition is affected when individuals are shown images of recordings during a CIT instead of words.
Last year, Medical News Today reported on a study claiming corneal reflections in photos could help solve crimes.