forming categories

In the article by Gelman (1994), she asserted that people will form categories based on physical, surface features, which, provides a means for assigning category membership. At the same time that this category is being formed, base on the intrinsic, unseen, underlying nature of the object, which is coined "essence" is being inferred about the object. Gelman shows that children are especially good at infering intrinsic properties in animals. Her research shows that 93% of children will refer to intrinsic properties of an animal to explain a biological event if no external cause for the event is present. Gelman also studied childrens assumptions about the innate potential of categories by asking them what the outcome for a kangaroo raised by a goat would be. She found that children will answer questions about animals in terms of category membership or innate potential, relying on knowledge about the nature of the animal, rather than the nurture the animal was given. Furthur research showed that 5 year-olds are very accurate at realizing that things can change as they grow (seed-tree, caterpillar-moth), and that it is the internal properties that are critical to the objects identity. They realized at this young age that "essences" will remain unchanged.
With all of this evidence showing that both categories and essences are learned or inferred at the same time, this leads me to think of how negative influence during this learning process can lead to prejudice. It appears that as children experience the world, they categorize the things that they observe, and make inferences about the nature of the the objects in these categories. If a child sees a person with a different skin color, and begins the automatic process of categorizing them, likely assigns similar essences that they have for themselves and other people. My question is this: to what degree will the child integrate this new person of different color into his/her same person category, and what influence do the parents have on assigning essences to this category? To try to answer this, I looked at an fMRI study by Jennifer Eberhart (2005). She examined people for differences in neurological processing of faces of different races. She found increased activations in many areas of the brain when observing faces of other races than that of faces of the participants race. This increased cortical activation is strongly correlated with areas involved in emotion and inhibition. These results suggest a possible hypothesis for my question: The essences of the different race, may be associated with negative emotion, and the increase inhibition may be due to conflict in the separation of the category that that is based on surface clues rather than internal properties of the other person. This still leaves the question of what role the parent plays in the assignment of essences to this race category. I hypothesize that the the parents input about that person; good or bad will become internalized in the child, thus, reinforcing the formation of a sub-category based on external rather than internal cues about the person. This internalization and categorization may account for the deep prejudice observed in some people.