How to Spot an Author in a Crowd

There are things that you notice when you've grown up around the arts. Or at least things you notice when you pay attention. String players lead with their heads, allowing their intellectual abilities to guide them forward both physically and mentally. Piano players lead with their hands. Dancers lead with their torsos. And the sign of a good actor is the seemingly deliberate and fluid actions that they make with a looseness and relaxed manner that suggests they could slip into any role of which they have been assigned, forming it and making it their own in a way only one who is stealing anothers identity can do, something I have tried and failed to master. Maybe that's why I've failed. Maybe I try to hard.
But as writer, we do the same thing. We steal the fictional identities of the people whose lives we control, molding it like a piece of clay until it's exactly how we like it. We lead with our hearts, working to rip the bits and pieces of our recollections and observations, bleeding it onto the pages that others, if we are lucky, will read. So where you might be able to spot a woodwind player in a city or an actor in a crowd, how do you spot an author?
The answer: They will always have a book with them.