Scent

I notice smells. I'm always trying to be aware of my surroundings with all of my senses, and I've particularly noticed that people leave a scent trail behind them when they walk. Everyone, not just the particularly perfumed or malodorous. I visualize it as the wake that trails behind a ship in the water, spreading out a long distance before finally melding into the ambient waves and disappearing. I can usually still smell someone even when crossing a point that they walked through fifteen or twenty paces ago. There's just a noticeable difference between most of the air that's floating around us and the air that was draped around a warm human body moments ago.

Sometimes I inhale as I'm walking for the sake of being conscious of my environment.

Sometimes I hold my breath for a long while. Maybe because I've held my breath as a calming technique since I was a little kid and it still brings me a small sense of peace. Maybe because I don't want to find out what you smell like today.

As a side-effect of this particular sort of mindfulness, I sometimes notice when there's a human-smell in the air when there should not be, and an abrupt primal instinct kicks in to scan the area for predators.