Steven Pinker on Common Knowledge, Mentalizing, and Coordination Games

Understanding Common Knowledge

• 💡 Common knowledge involves an infinite regress of embedded propositions about mental states, which seems implausible for human minds.
• 💥 It is crucial for coordination and social relationships, which are viewed as coordination games.
• 📌 Common knowledge can be generated by public, conspicuous events that everyone witnesses and knows everyone else witnesses, like a "bomb detonating."
• 💬 The concept is often implicitly understood, even if not explicitly named, and is reflected in metaphors like a "big matzah ball hanging out" in a romantic declaration.

Developing Theory of Mind

• 🧠 Mentalizing, or theory of mind, is the intuitive ability to understand what others are thinking or feeling.
• 🔬 Experiments, such as the false belief test (marble in a box), show that three-year-olds struggle to differentiate their knowledge from others', while four-year-olds correctly attribute false beliefs.
• 🧩 Recursive mentalizing, understanding what someone else thinks about another's thoughts, is more complex, with children typically mastering it around seven or eight years old.
• 🎭 Adults can generally handle three or four levels of mentalizing, especially when dealing with familiar scenarios that become "chunks" of knowledge.

Coordination and Focal Points

• 🎯 In the absence of common knowledge, people rely on common salience to coordinate, seeking something that "pops out" to everyone.
• 📍 Shelling points (named after economist Thomas Shelling) are solutions to coordination games, where a salient option helps individuals converge on a mutually beneficial outcome.
• ⚖️ Coordination games have multiple equilibria, and game theory alone cannot dictate which one to choose; instead, psychology and theory of mind guide the decision.
• 🤝 Examples include choosing a meeting place, driving on a specific side of the road, or negotiations where parties might "split the difference" or settle on a round number as a focal point.