In the west girls and boys are free to share a lot more physical proximity. They hug each other in public, may share a kiss on the cheek, spend time together as friends. There are no assumptions of romantic/sexual relationships as people tend to be more open when they are involved in one.
In many Eastern cultures physical proximity between opposite sexes is frowned upon. Till recently and still a lot in rural parts hugging, touching, spending time together can be considered taboo. People question a girl's character if she is seen alone with a guy, sharing a hug with a guy friend etc. I have had people complain that just because they had lunch with a friend or watched a movie together people question if there is a relationship.
Same sex friendships seem to have quite the opposite reaction specially when it comes to guys. Eastern cultures seem to be a lot more touchy. Men tend to share a lot of platonic physical proximity. You can watch it in reality shows, an eliminated guy will cry on the shoulders of another, other guys will console, place a kiss on the forehead in consolation. We view it merely as a reflection of friendship and looking out for each other, in the west such interactions between men tends to be viewed as gay.
In India infants and children are held and cuddled by friends, family, neighbors whereas in the west such affection is restricted to parents and very close family members.
French traditionally greet people with 'bizu', in parts of the middle east men lock lips, yet in other parts of the world such interactions are frowned upon or taboo.
What determines this human psychology of touch? How have different cultures taken on different interpretations of the exact same physical interaction? Does this difference of perception raise barriers and misunderstandings in communication? How often do we misunderstand or misread physical interactions based on our own psychological perceptions?