Blindspot: Hidden Biases of Good People
By Mahzarin R. Banaji, Anthony G. Greenwald

Blind Spot is an excellent read for anyone interested in the the concepts of mental models /bias and the influences they have on our opinions of and interactions with others. 

This particular study focuses on what I refer to as affinity bias, the desire or tendancy to help those who are most like ourselves.  While different from overt prejudice and seemingly innocuous on the surface, these behaviours ultimately exasperate problems such as social stratification. 

By unconsciously support those most like ourselves we may be unintentionally  adding to the problem.