Human beings have a remarkable ability to attribute meaning to the objects and events around them. Without much conscious effort, we are able to recognize the items in our environment as familiar ‘kinds’ of things, and to attribute to them properties that have not been observed directly. We know, for instance, that the banana on the kitchen counter has a skin that easily peels off, and that beneath the peel we will find a soft yellow-white interior. We know that the banana is meant to be eaten, and can anticipate what it will taste like. Such inferences spring readily to mind whether we observe the banana itself or, as with this paragraph, simply read or hear statements referring to bananas. The cognitive faculty that supports these abilities is sometimes referred to as ‘semantic memory’, and a key goal of much research in cognitive psychology is to understand the processes that support this aspect of human cognition.

One long-standing hypothesis places categorization at the heart of human semantic abilities. The motivation for this view is that categorization can provide an efficient mechanism for storing and generalizing knowledge about the world. As Rosch (1978) put it, ‘…what one wishes to gain from one's categories is a great deal of information about the environment while conserving finite resources as much as possible.’