Idea: Young animals of countless species have been observed engaging in play, exploring their environment, testing boundaries, and entering low-stakes simulations of behavior that will in adulthood become high-stakes (e.g. wrestling, hunting, dollhouses). In humans, playful exploration in this sense is associated with the sincere enthusiasm of discovery—young children can still be surprised or highly excited in the face of imminent newness. These patterns of behavior inevitably leave a trace in group epistemics; that is, there is a strong association in the culture, conscious or not, between affects like enthusiasm or playfulness and the status of an organism with much to learn.
Cool, then, functions at least partly as a signal of having thoroughly learned and mastered one’s environment (or body, or self). New employees and college freshmen are enthusiastic; vets and jaded seniors play it cool.
Instead of high interest and enthusiasm, cool greets objects and situations with a “seen it all before” attitude—inherently cynical in that it supposes strong limitations of possibility—that demonstrates worldliness and experience, taking a dominant social position over those exhibiting wonder or play. No surprise then that another component of cool is the ability to wield in-group references, i.e. the displaying of social, situational, and/or cultural knowledge with ease. Nor is it a surprise that “knowingness” is adjacent to cool. The knower acts doubly, showing an awareness of the sociocultural (i.e. fashion-field) reputations of his actions simultaneous with his act.
(A friend points out that high status humans “squirt” serotonin, a chemical that promotes the feeling of “wanting for nothing” and thus incentivizes homeostasis. This is in opposition to noradrenaline, potentially present at higher levels in lower status humans, which we might think of as the motivation chemical. I’m personally ignorant on the biology, so will leave it at that.)