"The everyday nature of interacting with stranger is a byproduct of urbanization, which has created a culture of dense populations with sparse interconnections," writes Stark. "Living in cities has made strangers into a multitude: we brush past thousands of them every day."
Now, with geolocation services like Foursquare and augmented reality applications on the horizon, what it means to be a stranger is becoming increasingly uncertain. Stark finds social behavior has a close relationship with public space, and the way people move through it. Indeed, she finds that there are "cognitive scientists who study the idea that perception, emotion, and attitudes are the processes of the body moving through space (rather than simply neural signals in the brain)."