Page 258 - Foundations of Cognitive Psychology : Core Readings

264 Eleanor Rosch

in the types of categories examined in Rosch and Mervis (1975) could be
represented in terms of counting attribute frequency (as in Neuman 1974),
in terms of storage of a set of exemplars to which one later matched the
input (see Shepp 1978 and the introduction to Part II of Rosch and Lloyd
1978), or in terms of explicit teaching of the prototypes once prototypicality
within a category is established in a culture (e.g., ‘‘Now that’s a real coat.’’)
In short, prototypes only constrain but do not specify representation and
process models. In addition, such models further constrain each other. For ex-
ample, one could not argue for a frequency count of attributes in children’s
learning of prototypes of categories if one had reason to believe that children’s
representation of attributes did not allow for separability and selective atten-
tion to each attribute (see Garner 1978 and the introduction to Part II of Rosch
and Lloyd 1978).

Two Problematical Issues

TheNatureofPerceived Attributes
The derivations of basic objects and of prototypes from the basic principles of
categorization have depended on the notion of a structure in the perceived
world—bundles of perceived world attributes that formed natural discon-
tinuities. When the research on basic objects and their prototypes was initially
conceived(Roschetal. 1976a),Ithoughtofsuch attributesasinherent inthe
real world. Thus, given an organism that had sensory equipment capable of
perceiving attributes such as wings and feathers, it was a fact in the real world
that wings and feathers co-occurred. The state of knowledge of a person might
be ignorant of (or indifferent or inattentive to) the attributes or might know of
the attributes but be ignorant concerning their correlation. Conversely, a person
might know of the attributes and their correlational structure but exaggerate
that structure, turning partial into complete correlations (as when attributes
true only of many members of a category are thought of as true of all mem-
bers). However, the environment was thought to constrain categorizations in
that human knowledge could not provide correlational structure where there
was none at all. For purposes of the basic object experiments, perceived attrib-
utes were operationally defined as those attributes listed by our subjects. Shape
was defined as measured by our computer programs. We thus seemed to have
our system grounded comfortably in the real world.
On contemplation of the nature of many of the attributes listed by our sub-
jects, however, it appeared that three types of attributes presented a problem
for such a realistic view: (1) some attributes, such as ‘‘seat’’ for the object
‘‘chair,’’ appeared to have names that showed them not to be meaningful prior
to knowledge of the object as chair; (2) some attributes such as ‘‘large’’ for the
object ‘‘piano’’ seemed to have meaning only in relation to categorization of the
object in terms of a superordinate category—piano is large for furniture but
small for other kinds of objects such as buildings; (3) some attributes such as
‘‘you eat on it’’ for the object ‘‘table’’ were functional attributes that seemed to
require knowledge about humans, their activities, and the real world in order