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Your brain waves could reveal what you forgot (or lied about)

A study with implications for criminal investigations finds that looking at a particular brain wave could help recover buried or hidden information.

During interviews and interrogations, detectives often ask subjects whether they recall pieces of information pertaining to a crime or crime scene. Because our brains are constantly processing huge amounts of information, it can be difficult or even impossible to recall data that wasn't salient enough to notice, at least consciously. And if information is incriminating, we might resist voluntarily giving it up.

Could an EEG, like the one shown here, hold the key to better lie detection?Video screenshot by Anthony Domanico/CNET

But what if such information could be extracted without relying on a subject's memory at all? According to a new study published in the journal Psychological Science, that could be possible via a particular brain wave known as P300, circumventing both our fallible memory and refusal to give up potentially incriminating evidence.

The study examined 24 subjects using the Concealed Information Test (CIT), a recognition test that examines whether a subject recognizes crime-relevant information. Each subject was equipped with a wearable camera that recorded information over a 4-hour period.

Video captured by the 24 subjects was analyzed by the researchers, psychologists John B. Meixner and J. Peter Rosenfeld of Northwestern University. The people were divided into two groups, 12 test subjects and 12 control subjects. For the test subjects, Meixner and Rosenfeld compiled individual lists of things the test subjects had seen over the course of the day, as well as similar things they hadn't seen. Say a test subject had seen a Trader Joe's, for example: that person's list would contain Trader Joe's and one or two similar stores like Whole Foods or Kroger.

While there were individual lists for the 12 test subjects, the researchers made a single generic list for the 12 control subjects. The researchers then read items off the list to the subjects, and measured their P300 brain waves. The control subjects, who were presented with a list of things they hadn't seen that day, showed no measurable change in P300 size.

When the test subjects heard the name of something they had seen the previous day, the P300 wave appeared larger than when they heard the name of something they hadn't seen.

"Perhaps the most surprising finding was the extent to which we could detect very trivial details from a subject's day, such as the color of umbrella that the participant had used," Meixner said in a statement. "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."

Further research will look at whether presenting images, video clips and other types of information will produce results similar to those to related to descriptive words -- preliminary work by the group suggests this will likely be the case. Additional research is needed to further validate the P300 effect in the CIT setting. Currently, the CIT is extensively used in Japan and some other countries, but hasn't been adopted in the US due to a lack of studies proving its validity and reliability in criminal settings.

This study is the first of its kind in that it validated the effect P300 has on recalling memory in the real world; previous P300 tests have been conducted exclusively on information presented in a lab environment.