Gettier contributed to what we know about the exemplar model, while Rosch contributed to what we know about the prototype model. Prototype and exemplar theories are both versions of statistical theories of concepts. Prototype theories hold that concepts represent categories by means of a summary of the typical properties that category members possess, while exemplar theories hold that concepts represent categories by means of a cluster of individual category members that may be used to extract the statistical central tendency of the category.
