A wink is a single binary bit of information. The eye is either open or closed. But, across a dinner table, or a crowded room, a wink can communicate so much: "I'm in on the joke." "I saw what you did." "I'm on your side, kiddo." The tiny gesture pulls meaning from circumstance, context and relationship, directs its beam and then condenses it into a fleeting twitch of an eyelid.
Social gestures like that put pay to the notion that rich meaning requires high bandwidth. The gentle or painful squeeze of a hand on a forearm is loaded with opposite meaning and, even if delivered by the same person in the same circumstance, the simple variant of pressure speaks volumes.