Our brains handle social hierarchies like physical hierarchies

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The part of our brain that helps us figure out where we are also helps with navigating social situations. (Unsplash/Christina @ wocintechchat.com)

Researchers from the University of California, Los Angeles, have discovered that the brain regions involved in processing spatial information are also involved in inferring social relationships and hierarchies, as they navigate attention shifts in both social knowledge situations and external spatial knowledge. 

In a paper published March 28 in NeuroImage, the UCLA social neuroscientists investigated which parts of the brain are engaged when individuals are processing social and spatial information. They found that the superior parietal lobule, a brain region known to be responsible for directing shifts of attention in external space, also encodes shifts of attention in internal representations of social relations. 

Carolyn Parkinson, an assistant professor at UCLA and senior author of the paper, explained to The Academic Times that as a social neuroscientist, her work uses tools from neuroscience to ask questions about how the brain processes social information. 

"One of the things that we're really interested in is how we think about and how we're impacted by patterns of social relationships, because humans create and navigate big, complex social worlds where we have to keep track of and think about lots of different complicated relationships between people," she said. "And it doesn't necessarily seem effortful because we're so good at doing it, but there's a lot that goes into the various aspects of social cognition that we just perform every day without really thinking twice about it."

According to Parkinson, scientists have previously theorized that there may be a relationship between the neural mechanisms that support abstract feats of social cognition, where we represent and reason about invisible relationships between people, and the mechanisms that support how the brain represents and reasons about relationships between concrete things, such as objects or locations in the physical world.

Even the language that people use to describe abstract information shows how the mind processes it, such as "top of the pecking order" and "low status" when discussing social hierarchies, according to the authors, as they "may not just be figures of speech, but rather, figures of thought that illuminate the structure of underlying mental representations."

Previous neuroimaging studies, including past work from Parkinson, have suggested there is considerable overlap in the brain regions used for processing spatial information and the regions used for processing abstract social knowledge, particularly in the posterior parietal cortex, which is known for planned movements, spatial reasoning and attention. One portion of the posterior parietal cortex, the superior parietal lobule, is involved with spatial orientation and supports shifts of attention both in the perceptual environment and in internal knowledge representations. The researchers primarily focused on this region for their work. 

The researchers recruited a sample of 30 adults in California who first completed behavioral tasks where they learned the social status hierarchy of a group of fictional people in a workplace through trial and error. In the first task, they learned about the relative social status of pairs of people and had to infer the relationships between other people who were not seen in order to gradually put together the whole social structure. And in the second task, they were asked to determine who was a given number of steps more or less powerful than another person in the hierarchy.

The participants later underwent functional magnetic resonance imaging scanning while completing task two for a second time, and then performing a separate eye movement task that tested their spatial shifts of attention in different directions. After that magnetic resonance scanning procedure, they performed a final behavioral task where they had to arrange the faces of the people in the social hierarchy in the way that they thought best reflected their power in the fictional organization.

"We wanted to see if we can use the patterns of brain activity that are evoked when they're doing this mental operation to tell [which] direction they are mentally navigating in the social hierarchy," explained Parkinson.

To interpret the magnetic resonance imaging data, the researchers used multivoxel pattern analysis, a method of analyzing the information contained in distributed patterns of neural activity, in order to compare and characterize these patterns in the participants as they completed the tasks.

All participants were accurate in their organization of the faces in the hierarchy. The majority ordered the faces vertically and a minority ordered them horizontally or diagonally. The authors used data analytic methods to test whether the superior parietal lobule encoded shifts of attention in space and social knowledge the same way, and they utilized "the mappings between locations in space and the social hierarchy that the participant indicated in the post-scan drag-and-drop task" to test if the neural response patterns evoked when shifting attention toward more powerful people in the social hierarchy resembled those evoked when shifting attention either upward or leftward in space, respectively. 

The researchers determined that response patterns in the superior parietal lobule, long tied to attention shifts in physical space, also informed the figurative directions to which people navigated in their internal representations of social knowledge.

"It seems like the same brain region is encoding how you're shifting your attention in social knowledge, and how you're shifting your attention in the space around yourself, but it's encoding those things in different ways," Parkinson said  — all brain regions encoding both social and spatial mental operations appeared to encode them in independent coding schemes despite their overlap, the authors said in the paper, "because of partially shared processing demands for these mental operations." 

When participants arranged the social hierarchy post-scan, this may not have accurately reflected their actual mental representations during the social task, which could be an explanation as to why the regions encode the operations differently. Or, it may be that differences in the neural encoding of directions in space and social knowledge reflect some differences in processing demands — maintaining accurate mental representations of social relations between people and of relative locations in space may require different levels of mental flexibility.

The authors noted that further research along these lines might examine how the brain supports mental navigation of different types of social relational knowledge, and how that compares to other kinds of mental operations.

"In the future it would be interesting to look at other kinds of social knowledge, and also maybe social knowledge that reflects people's real world knowledge — not just artificial things we teach them in the lab, which gives you a lot of control, but it's not accurate [for understanding] how people acquire social knowledge in the real world," Parkinson said.

The study, "How does the brain navigate knowledge of social relations? Testing for shared neural mechanisms for shifting attention in space and social knowledge" published March 28 in NeuroImage, was authored by Meng Du, Ruby Basyouni and Carolyn Parkinson, the University of California, Los Angeles.

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