In a sense, human beings are constantly playing games with one another. Whether finding one’s place in the pecking order, testing another’s mettle, angling for scarce resources or more desirable companionship, or striving to predict and influence others’ behavior, many and perhaps most of our species’ interactions can be fruitfully analyzed through the lens of game theory. One particularly chock-full area of recent research involves the technical term “common knowledge,” referring to cases where just about everybody knows that everybody knows a certain thing, and everyone is aware of that, and so on down an infinitude of self-referential rabbit holes that nonetheless remain socially germane.