How does the human brain interpret other people’s thoughts, make moral judgments, and comprehend belief systems? These questions have traditionally been the realm of philosophers and poets, but Rebecca Saxe is seeking — and finding — answers through scientific inquiry.

“It is one of the most mind-blowing facts about the entire universe — you get a bunch of cells, wire them up in a network, make them fire in patterns, and you get the human mind,” says Saxe, who became captivated by the intersection of the brain and mind while studying philosophy and psychology as an undergraduate at Oxford University. She earned a Ph.D. in brain and cognitive sciences at MIT in 2003 and became a professor in that department shortly thereafter.

Saxe specializes in social cognition, which hinges on our ability to understand another person’s perspective and realize that it can differ from our own. This ability, called theory of mind, underpins communication, empathy, morality, and religious and other forms of belief, and could be key to understanding psychological disorders characterized by social dysfunction, such as autism.

Using functional magnetic resonance imaging (fMRI), a scanning technique that reveals brain activity by measuring blood flow, Saxe was the first to discover that theory of mind has a specific command center in the brain — the right temporoparietal junction, or TPJ. That such a high-level cognitive process could occur in a distinct patch of cortex, rather than involve a constellation of regions or circuits, astonished many neuroscientists.

In subsequent studies using fMRI, Saxe verified that the brain response behind theory of mind, which develops around age four, “is extremely robust and reliable, like visual perception or motor control.” Recently, she investigated the hypothesis that children develop theory of mind by observing the faces and gestures of people around them. This would indicate that social cognition evolves differently in the brains of adults who are blind from birth. In a study comparing congenitally blind adults to their sighted counterparts, Saxe instead found that the theory-of-mind mechanisms in these subjects was “indistinguishable. The social brain network evolves perfectly fine in the absence of vision.” She is now testing the hypothesis that language shapes the development of theory of mind.

Saxe also explores social cognition’s role in how we make moral judgments. In another recent study, participants contemplate a scenario in which one person accidentally poisons another. Saxe found that activity in the right TPJ, where theory of mind resides, corresponds with a person’s willingness to forgive someone for causing unintentional harm. “In general, the amount of activity in this particular brain region during moral judgment predicts which moral judgment you make,” she says.

Currently, Saxe is designing experiments to test whether there is a relationship between theory of mind and autism. “What we know so far is that it looks like autism is a selective impairment in thinking about other people,” she says. That observation would explain the difficulty that autistic people have with communication and social interaction. In upcoming studies on autistic children, Saxe plans to use a new procedure that combines fMRI with live video to observe brain activity during real-time social interaction. This technique has the potential to pinpoint, for the first time, the neural anomalies behind autistic behaviors.

Whether untangling the physiology of autism or studying brain development in the congenitally blind, Saxe ultimately seeks clues to big questions about the human mind. “We’ll know a lot more in five years,” she says, as she leads the way.

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