Scientists scanning the human brain can now tell whom a person is thinking of, the first time researchers have been able to identify what people are imagining from imaging technologies.

Work to visualize thought is starting to pile up successes. Recently, scientists have used brain scans to decode imagery directly from the brain, such as what number people have just seen and what memory a person is recalling.

They can now even reconstruct videos of what a person has watched based on their brain activity alone. Cornell University cognitive neuroscientist Nathan Spreng and his colleagues wanted to carry this research one step further by seeing if they could deduce the mental pictures of people that subjects conjure up in their heads.

“We are trying to understand the physical mechanisms that allow us to have an inner world, and a part of that is how we represent other people in our mind,” Spreng says.

Imagining others

His team first gave 19 volunteers descriptions of four imaginary people they were told were real. Each of these characters had different personalities. Half the personalities were agreeable, described as liking to cooperate with others; the other half were less agreeable, depicted as cold and aloof or having similar traits. In addition, half these characters were described as outgoing and sociable extroverts, while the others were less so, depicted as sometimes shy and inhibited. The scientists matched the genders of these characters to each volunteer and gave them popular names like Mike, Chris, Dave or Nick, or Ashley, Sarah, Nicole or Jenny.

The researchers then scanned volunteers’ brains using functional magnetic resonance imaging (fMRI), which measures brain activity by detecting changes in blood flow. During the scans, the investigators asked participants to predict how each of the four fictitious people might behave in a variety of scenarios — for instance, if they were at a bar and someone else spilled a drink, or if they saw a homeless veteran asking for change.

“Humans are social creatures, and the social world is a complex place,” Spreng says. “A key aspect to navigating the social world is how we represent others.”

The scientists discovered that each of the four personalities were linked to unique patterns of brain activity in a part of the organ known as the medial prefrontal cortex. In other words, researchers could tell whom their volunteers were thinking about.

“This is the first study to show that we can decode what people are imagining,” Spreng says.

Unlocking brain’s personality models

The medial prefrontal cortex helps people deduce traits about others. These findings suggest this region is also where personality models are encoded, assembled and updated, helping people understand and predict the likely behavior of others and prepare for the future.

“The scope of this is incredible when you think of all the people you meet over the course of your life and are able to remember. Each one probably has its own unique representation in the brain,” Spreng says. “This representation can be modified as we share experiences and learn more about each other, and plays into how we imagine future events with others unfolding.”

The anterior medial prefrontal cortex is also linked to autism and other disorders in which people have problems with social interactions. These findings suggest people with such disorders may suffer from an inability to build accurate personality models of others. Further research could not only help diagnose these diseases, but also help treat such disorders, researchers say.