Interpersonal Distancing...

Its human psychology that we prefer to maintain a distance from a stranger... Here's the actual theory behind it from a psychology source... People surround themselves with a "bubble" of personal space that they claim as their own, and they tend to become stressed when other people invade their "bubble." Ashton and colleagues found that when they asked pairs of friends and strangers to stand at various distances from each other, both men and women felt more comfortable when an opposite-sex friend stood close (about 1.5 feet) than when a stranger of either sex stood at that distance.