It is sort of strange, but among the many people that walk around in the city, I think I can recognize fellow academics or librarians from a distance without talking to them. I talked to a few to check my hunch, and got it right nearly every time. It is impossible that I remembered the faces of all conference participants, but I think it is their mannerisms. The way they look a bit forlorn, clumsy in a way. They peer around and then look at a map to figure out their orientation and where to go, in a... librarian kind of way? The typical hesitation or internal debate in choosing a particular direction. Also the attire, perhaps? I can not quite pin it down, but it is as clear as a voluval tattoo would be. I recognize my own tribe.