I'm sitting on my porch, contemplating the day. A bloke on a Vespa drives by: I stare at him (Vespas being a rare occurrence here). He sees me staring, and waves as he drives by. I feel compelled to wave back.

Consider the exchange: two strangers acknowledge one person's interest. No words were exchanged, but information passed between the two. My noticing was noticed. An inference was made: that I was probably staring because of the Vespa. Interest is ascribed to the deviance: I think he's unusual, and he acknowledges my recognition of that. I have just confirmed his hypothesis that he is special because he drives a Vespa. By staring, I have confirmed his place in the world. By staring, I have revealed special knowledge, an awareness of normality and deviance. By waving back, I have confirmed my special knowledge, so now he knows there is one more person who recognizes the significance of the Vespa.

This is how identity is constructed, incrementally.