What some concepts might not be

Domain differences in the structure of artifactual and natural categories

“…Thus, it is now unclear whether the early research has any bearing whatsoever on conclusions about category structure (e.g., Armstrong et al, 1983). Since this realization, few studies have been conducted to directly investigate whether semantic categories have absolute or graded structure.…”

“…that some members of semantic categories have greater membership status than do other, less typical members (but, for alternative interpretations, see Armstrong, Gleitman, & Gleitman, 1983;Bourne, 1982;Landau, 1982). Furthermore, an overall high positive correlation between typicality and categorization is observed in most semantic categories (see, e.g., Diesendruck & Gelman, 1999;Hampton, 1998;McCloskey & Glucksberg, 1978;Rosch & Mervis, 1975).…”

Alternative strategies of categorization

“…One can generate pairs of extreme situations, such that just about everyone would agree that categorization is based on one strategy in one case and on a different procedure in the other case. Thus, if a person has to categorize two-digit numbers as odd or even, presumably all researchers would agree that the categorizer does it by applying the rule of 'Divisible by 2 or not' (Armstrong et al, 1983); but if that same person has to categorize novel people with respect to whether they are as friendly as the neighbors on their block, presumably most would agree that the categorizer now relies on memories of his or her neighbors (Kahneman and Miller, 1986). Note, however, an important aspect of this counterexample-the different putative categorization procedures are applied to different kinds of categories, where one category is part of a rule-based formal system and the other one is completely ad hoc.…”

Similarity-based categorization and fuzziness of natural categories

“…Reviewing arguments from Goodman (1970), Osherson and Smith (1982), Armstrong et al (1983), Murphy and Medin (1985), and others, Rips made the case that membership in natural categories was not primarily dependent on similarity. The argument is that the way in which category membership is determined is different from the way in which typicality is derived.…”