​What does it mean to be social? For science, a new definition

Think about the last time you called it a night, ordered takeout and spent some quality time alone. Maybe you just had a long week at work and the last thing you want to do is be around a bunch of other people. You may think deciding to stay in is anything but social, but according to neuroscientists at the University of Chicago, binge-watching Netflix by yourself is just as social as going to a party.

“Our definition of sociality, based on the human idea that being around other people is inherently good, is not serving us well,” said Peggy Mason, professor of neurobiology at UChicago. In an article published Nov. 8 in the Proceedings of the Royal Society B, she and Haozhe Shan, a former research assistant in Mason’s lab who is now at Harvard, propose a new definition of sociality as any behavior or biological process that is influenced by the presence of others.

The article is part of a special feature of the Proceedings focused on the unique role of humans as subjects for scientific research. Are humans simply another animal model for study, like rats or fruit flies? Or does our intelligence and consciousness set us apart in ways that don’t really apply across the biological spectrum?

In an introductory article to the feature, Sarah Brosnan, a behavioral psychologist at Georgia State University, and Erik Postma, an evolutionary biologist from the University of Exeter, write about this conundrum, and the disconnect they see among their “human” colleagues who primarily study human biology and behavior and “non-human” colleagues who study other animals.

“The implicit assumption that we are somehow outside of biology … not only blinds us to cases in which other species might be better models for a given question than are humans, but also means that we fail to see how research on ourselves has the potential to cross species-boundaries, informing us about the animal kingdom at large,” they write.

Mason and Shan propose a definition of sociality that avoids drawing distinctions between human and non-human perspectives. The pair argue a behavior or process is social if it’s influenced by the presence of another individual. That includes both going out with your friends or spending the night alone, because both decisions are based on your desire to interact with other people. If you act differently when you’re around others (or actively avoid being around them), that behavior is social.

But for the sake of science, Mason and Shan want to extend this definition to all animals and biological processes: Rats, like the ones Mason studies in her lab, which help out cage mates in distress; bacteria that trigger digestive processes in the gut; or sea stars that move an appendage when they crawl over each other in a tide pool.

“There’s a lot of power in having an extremely simple definition of sociality,” Mason said. “It allows you to study humans and animals, from other mammals all the way down to sea slugs.”

The new, simplified definition allows researchers to categorize processes as truly independent or social, and the degrees to which social interaction affects that behavior. How long does it take a single rat to collect several pieces of food when it’s by itself versus when it’s with a group? How do levels of the stress hormone cortisol change when humans are introduced to strangers?

A simple definition of sociality provides a range of measures for behavior and processes that can be tested with the scientific method. It also frees the concept of sociality from added valence, or moral judgments based on human ideas about whether a behavior is “good” or “bad.” A rat that turns down food to help free another rat from a trap is displaying what looks like a human version of empathy. But when a human parent shows empathy for a child who skinned her knee, we also could be acting on the same biological impulses as the rat.

Other social actions can be fraught with conflicting moral judgments. Should a parent give money to a teenager who is struggling with addiction, or cut them off out of tough love? Depending on your perspective, either choice could be the right decision. But in a new, stripped down definition of sociality, neither one is a morally superior or “good” act. They’re simply social behaviors driven by the presence of another individual.

Mason said that a scientifically clear definition of sociality will help better understand conditions like autism spectrum disorder, which is marked by varying degrees of avoidance or indifference to social contact. It can also help scientists begin to understand the evolution of social behavior in animals. As she and Shan write in the article, the neuroscience that underlies social behavior is ripe for exploration, and perhaps more necessary now than ever.

“While knowledge of the genetics, development and physiology of single individuals accrues, an understanding of the biological mechanisms by which individuals interact has barely budged,” they write. “Yet many of society’s greatest problems derive from an inability of humans to get along with each other.”