You're on a train, staring out the window at power lines, green planes and sky. Your mind wanders. You think of things that happened years ago, people still important in your life. You recall an exchange, you relive the feel of it; embarrassment, adoration, indifference, adventure, but context-dependent and with a specific, complex taste; you're watching rows of hedges, trees and sheep flash by, but in your mind's eye you see streets, places, a room where years ago someone close to you slept. The room most likely remains but you know nothing of the persons living there now; they never enter your mind in any way, why should they? Your friend lives elsewhere now, lives where the train is heading. For three hundred and thirty two seconds your brain attracts around those memories - the room, the bathroom, food and conversations you had there, films you watched - then stops, and you snap out of it, reach for your bottled water, and reconnect with your surroundings; with the people moving or sitting still around you. You don't know why your mind drifted to those particular memories, or what made it stop suddenly - or rather, you DO know, about quasi-stable patterns of brain activity, maintained by dopamine and obvious given your destination - but why that PARTICULAR chain of thoughts and memories, and why the sudden stop? You imagine the dyanmics of your brain, imagine a brain-shaped animation of swirling electrical potential, action potentials, ever-changing, save for brief periods where stable configurations are reached that attract the swirling mass around a recognizable shape, a place, a thought, a memory, before loosing interest and drifting off. You look around again, search the environment for stability, attraction, dopamine. The woman next to you in black, with the clean features, the headphones, the short hair and the eyebrows. The landscape outside, darker now; houses, horses, a town. There's nothing there to keep you, and your mind begins to drift again. It makes you sad, restless, and you put the music back on.