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Marian Berryhill

How Our Brains Go the Distance

Denver fans are glad that game is behind them. I’m looking forward to the end of this snow. They’re close friends. We’re distant cousins. He’s down in the dumps. She’s on top of the world.

People think about distances all day… long. Distance can describe physical spaces (a far-flung city; a nearby store), time (distant past; near future), and social relationships (near-and-dear pals; a quarreling couple needing some space).

Researchers have long thought that these various examples of “psychological distance” are represented by some of the same circuits in the brain. A new brain-imaging study strongly bolsters the idea, finding that certain patterns of neural activity underlie all of our judgments about distance — whether in space, time, or the social realm.

The results makes sense, the researchers say, given that all of these distances have something in common: They give us a way to move beyond the visceral, here-and-now experience of our lives. More provocatively, this ability to “go the distance” might be uniquely human.

The logic is that other animals live mostly in the present: They feel hot or cold, hunger or thirst, fear or lust. They perceive color and motion. And they can reach into the future — slightly. “They traverse space, they traverse time, and so they can connect these things together and plan for the future, at least in the short-term,” says senior investigator Thalia Wheatley, an associate professor of psychology at Dartmouth College.

Humans seem to have taken this spatial perception and repurposed it for more abstract cognition, Wheatley says. “We can think 20 years in the future, and we have fluid and dynamic social networks.” My calendar application allows me to feel anxiety about a deadline months away, while an email exchange can make me feel closer to someone across the ocean.

In the new study, published last week in the Journal of NeuroscienceWheatley’s team scanned the brains of 15 adults as they made judgments about different kinds of distances.

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Marian Berryhill

Participants sometimes saw pictures of objects, such as the breads at right, and were asked to judge which was closer. Or they’d see photographs of their friends and of acquaintances and say which was more familiar. On yet other trials they’d see time-related phrases on a screen — such as “DECADES FROM NOW” and “IN AN INSTANT” — and judge which was sooner.

A few older brain-imaging studies have looked at the neural underpinnings of psychological distance. That research, though, focused on the intensity of brain activation in a given region. The new study, in contrast, subdivided brain regions into grids and compared the activity from one square to the next. “It allows you to look at not just where in the brain, but how information might be organized in that area,” says Carolyn Parkinson, a graduate student in Wheatley’s lab who, together with Wheatley, designed and carried out the study.

It turns out that the concept of a far distance, whether in the spatial, temporal or social domain, is encoded by a particular pattern of activity within a brain region called the right inferior parietal lobule (IPL), whereas the concept of a near distance corresponds with a different pattern in the same region.

What’s more, when the researchers trained a computer algorithm to distinguish between brain scans of far and near stimuli in one domain (such as physical space), that same algorithm could distinguish between far and near stimuli in the other domains with an accuracy of about 70 percent. This was true no matter which domain the algorithm was originally trained to recognize. “It was above chance in every single test, which suggests a really robust result,” Parkinson says.

Other researchers are impressed by the results and intrigued by their implications.

“I think this paper is an excellent addition to the rich body of work on how spatial representations are reused for thinking about other more abstract domains,” notes Lera Boroditsky, an associate professor of cognitive science at the University of California, San Diego. Boroditsky has published some fascinating studies about language metaphors, showing, for example, that the way people talk about time matches the way they think about it.

These sorts of studies, she adds, might explain why humans can “[go] far beyond those things observable through physical experience to invent sophisticated notions of number and time, theorize about atoms and invisible forces, and worry about love, justice, ideas, goals, and principles.”

What most surprised me about this research is its possible connection to empathy and “theory of mind,” or the ability to take the mental perspective of someone else. About a decade ago, researchers linked theory of mind to a specific region in the brain: the temporo-parietal junction (TPJ). Intriguingly, the TPJ region encompasses the IPL.

Theory of mind may be another way that we have evolved to look beyond our immediate, individual perspective, notes Nira Liberman, a social psychologist at Tel Aviv University. “We predict the behavior of other people by forming abstract mental constructs,” she says. “All these different ways of traversing immediate experience were and are achieved by abstract mental representations.”

This post is itself moving into an abstract realm, and I’ll end it with a further step into speculation. Wheatley has a theory that all of these findings could help explain why we tend to empathize with things that are close to us in physical space, time, and social space. Journalists are acutely aware of this “empathic myopia.” It’s hard to get readers invested in a story about the dire consequences of global warming that may be a century away, or about the plight of orphans living on the other side of the world.

Wheatley’s team is thinking about how to use brain scans to test the theory. For instance, they might have participants read stories about an event inside of the scanner and then observe whether their IPL activity changes when the stories emphasize physical or temporal proximity.

“Our paper demonstrates that the human brain evolved to make a critical decision about proximity to self: Is this thing happening right here, right now, to me or someone close to me?” Wheatley says. “In other words, why should I care?”