Brain Scans Can Now Tell Who You’re Thinking About

Beware stalkers, these neuroscientists can tell who you’re thinking of. Or, at least, the kind of personality he or she might have.

As a social species humans are highly attuned to the behavior of others around them. It’s a survival mechanism, helping us to safely navigate the social world. That awareness involves both evaluating people and predicting how they will behave in different situations in the future (“Uh oh, don’t get him started!”). But just how does the brain represent another person’s personality?

To answer this question a group of scientists at Cornell’s College of Human Ecology (whatever that means) used functional magnetic resonance imaging (fMRI) to measure neuronal activity while people thought about different types of personalities. The 19 participants – all young adults – learned about four protagonists, all of whom had considerably different personalities, based on agreeableness (e.g., “Likes to cooperate with others”) and extraversion (“Is sometimes shy”). They were then presented different scenarios (such as sitting on a bus with no empty seats and watching an elderly person get on) and asked to imagine how each of the four protagonists would react.

The study’s lead author, Nathan Spreng, said they were “shocked” when they saw the results. The brain scans revealed that each of the four distinct personalities elicited four distinct activity patterns in the medial prefrontal cortex, an area at the front of the brain known to be involved in decision making. In essence, the researchers had succeeded in extracting mental pictures – the personalities of others – that people were thinking of.

The study was published in the March 5 issue of Cerebral Cortex.

Sizing up the personality of another or thinking what they’re thinking is unique to social animals and in fact to do so was until recently thought to be uniquely human. But there’s now reason to believe the network – called the ‘default network’ – is a fundamental feature of social mammals in general. As Spreng explained in an email, “Macaque [monkeys] clearly have a similar network, observable even in the rat. All of these mammalian species are highly social.”

The fact that the mental snapshot of others was seen in the neurons of the medial prefrontal cortex means the current study may have implications for autism, Spreng said in a Cornell University news release. “Prior research has implicated the anterior mPFC in social cognition disorders such as autism, and our results suggest people with such disorders may have an inability to build accurate personality models. If further research bears this out, we may ultimately be able to identify specific brain activation biomarkers not only for diagnosing such diseases, but for monitoring the effects of interventions.”

Previous work has shown that brain scans can tell us a lot about what a person’s thinking. With an array of electrodes placed directly on the brain, researchers were able to decode specific words that people were thinking. In another experiment fRMI scans of the visual cortex were used to reconstruct movie trailers that participants were watching.

Much of neuroscience explores how the brain processes the sensory information that guides us through our physical environment. But, for many species, navigating the social environment can be just as important to survival. “For me, an important feature of the work is that our emotions and thoughts about other people are felt to be private experiences,” Spreng said. “In our life, we may choose to share our thoughts and feelings with peers, friends and loved ones. However, [thoughts and feelings] are also physical and biological processes that can be observed. Considering how important our social world is, we know very little about the brain processes that support social knowledge. The objective of this work is 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.”