Introduction Semantic memory contains the knowledge a person has about words, their meaning, what they refer to, and how words relate to each other (Tulving, 1972). Early models of semantic memory (such as that proposed by Collins & Quillian, 1969) represented word meanings as a hierarchy of features arranged in levels from the most general (e.g. living thing) to the most specifi c (e.g. robin). Properties of objects were stored in a hierarchy from most general to most specifi c. Properties true of animals in general (e.g. has skin, breathes) were stored at the animal category level, while properties true of particular animals (e.g. long ears) were stored at more specifi c levels (e.g. rabbit). Information in the hierarchy could be accessed at any level: at the most specifi c (e.g. robin), or at any of the more general levels (bird, animal, living thing).