Brain scans that can read a person’s secret intentions even before they act have been demonstrated by researchers.

In a recent study, the technology was 70% accurate at predicting whether participants planned to add or subtract a pair of numbers. Paralysed people may one day be able to use devices based on the technique to carry out complex actions, the researchers say. However, ethical concerns have been raised about its possible use in interrogation.

John-Dylan Haynes at the Max Planck Institute for Human Cognitive and Brain Sciences in Leipzig, Germany, and colleagues recruited eight people for their trial and placed each of them in a brain scanning machine that produced computed tomography (CT) images.

While participants had their brains scanned, they were asked to secretly decide whether they would add or subtract two numbers due to appear on a screen in front of them. After a pause of a few seconds, they then viewed the two numbers and gave their answer.

Train times

Once the computer program designed to interpret the brain scans had been “trained” on 40-minutes-worth of calculations by a participant, it could predict their calculating intention with 70% accuracy. Haynes explains that the computer program could do this by focusing on the pattern of activity in a brain region known as the medial prefrontal cortex.

“It’s important to see if we can further increase the accuracy” of the brain scan tests, he says, adding that it might be achieved by training the computer for a longer period of time.

According to Haynes, devices that pick up on brain activity in this region could one day help people with paralysis more easily perform complex actions – such as composing sentences on a computer – with thought alone.

Think of a letter

Previous technology has relied on signals from the brain’s motor region to enable paralysed patients to write sentences this way. But this involves the tedious task of moving a cursor across the computer screen to select from the alphabet. Haynes says using signals from the medial prefrontal cortex might enable people to simply think of the letter.

Neuroscientist Read Montague of the Baylor College of Medicine in Houston, Texas, US, says the findings add to a growing body of evidence that decisions can be predicted by observing the medial prefrontal cortex. “There are findings now that show that [activity in this brain region] can predict decisions to purchase an item for money or to choose a specific numerical ‘liking’ level for art,” he says.

Brain-scanning "mind reading" techniques raise ethical issues, however, and using such a tool to predict whether or not a person intends to commit a crime, for example, is contentious and should be debated by society now, Haynes believes.

Journal reference: Current Biology (DOI: 10.1016/j.cub.2006.11.072)