In new research, professor of linguistics Charles Yang and colleagues find that a formula originally developed to explain language acquisition in children can also explain how we absorb social norms.
2 min. reads
Think back to the first week at a new job, at a new school, in a new city. You weren’t sure whether to say “hi” to neighbors in passing or keep your eyes down. You didn’t know whether to speak up in meetings or hang back, to call people by their first names or formal titles. Then, one day, it clicked. Suddenly you knew what to do.
How exactly do we learn those unspoken social rules? A recent study in Proceedings of the National Academy of Sciences by Charles Yang, professor of linguistics and computer and information science at the School of Arts & Sciences and colleagues proposes a theory: The same cognitive law that governs how toddlers learn language also applies to learning social conventions.
Social conventions are arbitrary customs that influence everything from how close we’ll stand to a stranger to whether we shake hands or kiss on the cheek. The two dominant theories for how people learn these conventions comprise the imitation model, where you copy the person with whom you most recently interacted, or the optimizer model, where you conform to whatever’s repeated most frequently.
Yang wasn’t satisfied with either. “Something didn’t feel quite right about this kind of decision making,” he says. “And the reason I didn’t feel quite right about it really came from language.”
Previous linguistics research on language acquisition produced a mathematical formula called the Tolerance Principle that predicts exactly when that shift happens. That formula states that a pattern becomes a rule only when exceptions are very rare compared to the majority. Yang had a hunch that same threshold might govern social learning.
To test this theory, Yang and his co-authors used a game where online participants saw a picture of a stranger’s face and had to guess their name. They were then randomly paired with another player; if both players guessed the same name, they earned a reward. If not, they lost points. The names themselves were arbitrary—what the researchers wanted to know was not which name people chose, but how and when they committed to one.
The data showed two important patterns: Groups of players, regardless of size, consistently converged on a name in about 30 rounds. When 25% or more of the group consisted of “defectors”—fake players who always advocated for a different name and refused to bend to the group’s will—the name they suggested eventually became the established convention.
When Yang crunched the numbers, he found that the Tolerance Principle predicted both results. And when the team tested it against the actual round-by-round choices participants made, it was the most accurate model by far: It correctly predicted what someone would do next nearly 9 times out of 10, compared to about 8 times out of 10 for the imitation model and roughly 6 out of 10 for the optimizer.
The results suggest that learning social conventions is likely a two-part process. First, before enough evidence has accumulated, people stay flexible, choosing among options at random, weighted by how often each has come up. But once a majority of recent encounters conform to a rule, a convention snaps into place.
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