Categorical Perception - Categorization

Categorization

A category, or kind, is a set of things. Membership in the category may be (1) all-or-none, as with "bird": Something either is a bird or it isn't a bird; a penguin is 100% bird, a dog is 100% not-bird. In this case we would call the category "categorical." Or membership might be (2) a matter of degree, as with "big": Some things are more big and some things are less big. In this case the category is "continuous" (or rather, degree of membership corresponds to some point along a continuum). There are range or context effects as well: elephants are relatively big in the context of animals, relatively small in the context of bodies in general, if we include planets.

Many categories, however, particularly concrete sensori-motor categories (things we can see and touch), are a mixture of the two: categorical at an everyday level of magnification, but continuous at a more microscopic level. An example of this is Color categories: Central reds are clearly reds, and not shades of yellow. But in the orange region of the spectral continuum, red/yellow is a matter of degree; context and contrast effects can also move these regions around somewhat. Perhaps even with "bird," an artist or genetic-engineer could design intermediate cases in which their "birdness" was only a matter of degree.