No Boys Allowed: Hostile Environments

Those who create a hostile environment are often unaware of the level of hostility they are creating, or the effect it has. No white people at a black church; many of the members may assume that whites stay out of the church because they don't WANT to come in and join them. They may not be aware that they are sending social signals that say "STAY AWAY, WE WILL TREAT YOU BADLY" (or that fellow memb
ers are sending these signals). The same thing happens often in male dominated groups toward females quite often; no females in a math class, so the members of the class assume females don't "like" or don't "get" math, but the reality is that many of the participants send overt social signals to females that they are not welcome, and will not be treated with any kind of normal courtesy. This hostile environment group behavior can be seen almost anywhere there is a group of humans who have physical traits in common with each other.
And even within those groups, subgroups are created as well; a group of women from India may separate others in the group according to skin tone, for example.

http://gpi.sagepub.com/content/14/6/845.abstract
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