“In contrast, the terms “black” and “working class” are laden with the baggage of associations, perhaps some of them positive, but many of them negative. When a person is labeled “black,” we’re primed to perceive the characteristics that we tend to associate with “blackness” more generally, which is why students drew racially ambiguous faces with typically black features when they were told the face belonged to a “black” person. Participants in the experiment at Princeton similarly associated Hannah’s working-class background with diminished intellect, so they tended to emphasize her failings and overlook her strengths when they watched her complete an academic test.”
http://theweek.com/articles/464854/how-labels-like-black-working-class-shape-identity