Essentialism, concepts, and surprises.

Schemas, stereotypes, concepts, theories, beliefs. These are all terms which have been mentioned in class discussion to help explain how we, as humans, group objects, people, and events in the world into efficient categories. Certainly no one expects all of these concepts to be completely correct, but it is amazing that we can even develop such an elaborate network of theories about the world and how it works. It is interesting to note that these concepts are often formed based on what is most useful to us, rather than what is correct. As children, and even adults, explore the world, they find ample evidence to establish categories, and to refine the catogories they have already established. The theory of essentialism suggests that we believe animals and objects have a deep, true "nature" or "essence" that makes them what they are. As I will elaborate later, it is interesting to think about how contradictory evidence about the "nature" of a category might prompt us to wrestle with our concepts.
So how do we develop these concepts, or theories in the first place? The classic "defining features" view suggests that each concept or category has a set of necessary and sufficient attributes that its members must have to belong to that category ("necessary" means it is a required attribute, and "sufficient" means that the given attributes define the category). While this seems simple enough, one finds that it can be difficult to categorize certain items, or to label which attributes separate different categories. The "probabilistic" view suggests that we group members into a category using cue validities, or how predictive an attribute is of one category compared to another category. If a member has strong cue validities, it is typical; the basic level is the category level at which cue validities are greatest. We use the terms for basic level categories most often in everyday language (i.e. car, dog, flower v. volkswagen, terrier, daisy). But what is the underlying reason of category membership? The "theory" view explains this, and can be viewed in conjunction with the "probabilistic" view. The theory view suggests that there are causal explanations for why members belong to a certain group. The "theory" theory extends a form of this idea to all of cognitive development, stating that children are "little scientists" who develop and revise their theories based on their experience. One explanation of the nature of these theories is Essentialism. Whew, that was a bit long.
Okay, so back to Essentialism. There is ample evidence that both children and adults use essentialism as they create and manage concepts. For example, young children, who are generally very sensitive to perceptual stimuli, will attribute the characteristic of a category member to a new animal, rather than the characteristic of a perceptually similar animal (bird v. bat study). Adults assumed that people of the same race would always have more similar DNA that people of different races (DNA compared to essence). From personal experience, I would say that essentialism can often be applied to more complex concepts as well, such as social or religious groups, topics of study, etc., in addition to natural things and artifacts. I often will find evidence to contradict a new concept I've developed, and find myself asking (not in so many words perhaps), "Well, if this new information is true, what really is a ____?" This question reflects the crux of essentialism: that a true "essence" exists for everything, even if we don't know what it is. As I find new information, I revise my theory of what the category's "essence" is, but even if new information contradicts my theory, I just alter my theory. I don't discard the assumption that the essence exists.