Why independent cultures think alike when it comes to categories: It’s not in the brain

Imagine you gave the exact same art pieces to two different groups of people and asked them to curate an art show. The art is radical and new. The groups never speak with one another, and they organize and plan all the installations independently. On opening night, imagine your surprise when the two art shows are nearly identical. How did these groups categorize and organize all the art the same way when they never spoke with one another?

The dominant hypothesis is that people are born with categories already in their brains, but a study from the Network Dynamics Group (NDG) at the Annenberg School for Communication has discovered a novel explanation. In an experiment in which people were asked to categorize unfamiliar shapes, individuals and small groups created many different unique categorization systems while large groups created systems nearly identical to one another.

Source

If people are so different, why do anthropologists find the same categories, for instance for shapes, colors, and emotions, arising independently in many different cultures? Where do these categories come from and why is there so much similarity across independent populations? “If I assign an individual to a small group, they are much more likely to arrive at a category system that is very idiosyncratic and specific to them,” says lead author and Annenberg alum Douglas Guilbeault (Ph.D. ’20), now an Assistant Professor at the Haas School of Business at the University of California, Berkeley. “But if I assign that same individual to a large group, I can predict the category system that they will end up creating, regardless of whatever unique viewpoint that person happens to bring to the table.”

The explanation is connected to previous work conducted by the NDG on tipping points and how people interact within networks. As options are suggested within a network, certain ones begin to be reinforced as they are repeated through individuals’ interactions with one another, and eventually a particular idea has enough traction to take over and become dominant. This only applies to large enough networks, but according to Centola, even just 50 people is enough to see this phenomenon occur.

Adapted and abridged from Source (University of Pennsylvania. “Why independent cultures think alike when it comes to categories: It’s not in the brain: In contrast to prior hypotheses, this experiment shows that people are not born with category systems already in their brains.” ScienceDaily. ScienceDaily, 12 January 2021.)

Guilbeault, D., Baronchelli, A. & Centola, D. Experimental evidence for scale-induced category convergence across populations. Nat Commun 12, 327 (2021). https://doi.org/10.1038/s41467-020-20037-y