Steven Pinker Knows When No One Knows that Everyone Knows

"Before boarding a flight to South Africa in 2013, Justine Sacco sent a sardonic joke to her 170 Twitter followers: "Going to Africa. Hope I don't get AIDS. Just kidding-I'm white!" By the time her plane landed, she was the number-one trending topic worldwide, fired from her job, and branded a racist by millions of strangers. What happened wasn't simply outrage at bad humor. It was the sudden creation of "common knowledge.""

""It's not enough that everyone knows something; it becomes common knowledge only when everyone knows that everyone knows it, and everyone knows that everyone knows that everyone knows it, and so on." That recursive certainty transforms diffuse awareness into coordinated action. And "the dynamic of punitive mobbing," as Pinker notes, "is a recurrent vulnerability of human societies." "The leap is not from ignorance to knowledge," Pinker explains, "but from private knowledge to common knowledge.""

Common knowledge occurs when information becomes recursively shared so that everyone knows that everyone knows, and so on. Common knowledge forms through repetition, salience, visible norms, and shared signals that make awareness public and mutually obvious. Self-censorship, preference falsification, and pluralistic ignorance can keep beliefs private and prevent collective coordination. When private knowledge becomes common knowledge, coordinated behavior can follow rapidly, enabling actions ranging from reputational punishment to mass political mobilization. Social media and salient public cues accelerate the shift from private to common knowledge, creating vulnerabilities to rapid collective punishment and large-scale social change.

Read at Psychology Today