Feature Centrality as Conceptual Immutability

Previously I wrote that, given an object category defined over object representations, a prototype might be a set of features distinguished by some nice semi-formal properties:

1.  Prototype feature values are individually typical of the category, so that p(feature value is true of object | object is a category member) is high, and
2. A prototype feature value set is jointly diagnostic of category membership, so that p(object is category member | all the prototype feature values are true of the object ) is high.

This was meant as a plausible weakening of the folk intuition of category essentialism, wherein categories are defined by individually necessary and jointly sufficient criteria.

I also had some underwhelming speculation about replacing typicality with average values for graded and scalar-valued features (meant to capture the notion of "feature centrality"), and a little rant about fuzzy\graded category membership judgements being the result of individuals equivocating between similar but distinctly-motivated categories when they don't have domain expertise or introspective fluency to articulate the criteria distinguishing membership.

I've since mostly given up on the conception of prototypes as weakened-essence feature sets for categories. The experience that motivates people to talk about prototypes of object categories is just mental imagery of category members, which from the outside view is something like inferences about perceptual features of category members. Since these inferences aren't necessarily tied to memories of the situations from which the category's concept was learned, we usually think of prototypes as being unnamed and source-unsituated.

I've also since found a much more persuasive notion of feature centrality: the authors of "Feature Centrality and Conceptual Coherence" (Sloman et al., 1998) give an account of central features of a concept as being those features which are less mutable, in the senses that other object-features depend upon the central ones (within the subject's intuitive explanations of category feature co-occurrence), such that imagining mutations to central features (while maintaining explanatory coherence over the object features) may result in large downstream changes of dependent\peripheral features, with the possible effect of excluding the hypothetical object from category membership. Breathing is a central feature of the concept of birds, because we have difficulty imagining a bird which has never taken breath, except for example if it is stillborn, or if it's an ornament that looks like a bird, et cetera.

Fuzzy membership is still dumb though.