However, since at least the pioneering experiments on prototypes (Rosch 1973(Rosch , 1975, it has been known that, for a given semantic category, certain member concepts are consistently understood as more central to the category than others (even when controlling for clearly confounding factors such as frequency) (Coleman and Kay 1981;Medin, Altom, and Murphy 1984;Lakoff 1990;Hampton 2007).
wordNet and similar resources fail to capture the fact that category membership is a gradual semantic phenomenon.