"One product of the development of logical operations is the evolution of categorical thinking. Therefore arguments about the kind for world categories represent and the nature of categorical representations have implications Piagetian theory. [...] Rosch and her colleagues have contrasted the artificial world of concept-learning experiments with the natural world in which people construct and use concepts. They assert that the two worlds are so different that one cannot use the setting for concept-learning experiments or the models used to represent that setting (e.g., equivalence categories and truth tables) to represent natural category formation" (46-7).
"In concept-learning tasks [...] the concepts or category system representing the set is defined by selection mechanism that isolates or abstracts a single dimension or combination of dimensions on which objects vary which ignoring other aspects of the set. Both the lack of structure in the concept set and the nature of the abstraction processes dictate a definition of category intension in terms of necessary and sufficient defining features. All exemplars possess a particular property, and every exemplar that that has that property is a member of the set. All nonexemplars lack the defining property. Consequently, category boundaries are discrete and sharp" (47).
"Human representations are best accounted for by the structure of the environment rather then by nature of abstractions imposed on the environment. [...] Rosch's theory stresses an environmental determinism absent in Piaget. [...] Because the world has some but not complete structure, categories lack sharp boundaries. Categories also have an internal structure in which no one intensional property defines the set and creates equivalent instances. [...] In summary, natural categories are not defined in terms of a set of necessary and sufficient features but in terms of features that are more or less characteristic of overlapping distributions. Categories are detected, not abstracted" (49).
Compare the following in the section "are categories in nature?" with my linked post above:
"My current interpretation of Bhaskar's 'categories are real' is that the categories we perceive (and enact) are not arbitrary and that they arise from mechanisms, processes, and structures in the Real. Nature does not produce trees vs. shrubs—it does not contain these human-invented categories. But there is something in nature (having to do with how genetics and reproduction work) that clusters
living objects with similar properties, such that our perception of the world as containing trees and
shrubs is mostly accurate. [...] Yet, to follow Embodied Realism, any category that we actually have or use, such as tree or force, can only be an approximation of what exists in nature. It is misplaced concreteness to assume that objects in nature are constrained to manifest according to any known
category — though we can assume that nature produces different types of things and thus contains