Page 255 - Foundations of Cognitive Psychology : Core Readings

Principles of Categorization 261

mines prototype formation and category processing appears to be an artificial
exercise.

Effects of Prototypicality on Psychological Dependent Variables

The fact that prototypicality is reliably rated and is correlated with category
structure does not have clear implications for particular processing models nor
for a theory of cognitive representations of categories (see the introduction to
Part III of Rosch and Lloyd 1978 and Palmer 1978). What is very clear from the
extant research is that the prototypicality of items within a category can be
shown to affect virtually all of the major dependent variables used as measures
in psychological research.

Speed of Processing: Reaction Time
The speed with which subjects can judge statements about category member-
ship is one of the most widely used measures of processing in semantic mem-
ory research within the human information-processing framework. Subjects
typically are required to respond true or false to statements of the form: X item
is a member of Y category, where the dependent variable of interest is reaction
time. In such tasks, for natural language categories, responses of true are
invariably faster for the items that have been rated more prototypical. Further-
more, Rosch et al. (1976b) had subjects learn artificial categories where proto-
typicality was defined structurally for some subjects in terms of distance of a
gestalt configuration from a prototype, for others in terms of means of attrib-
utes, and for still others in terms of family resemblance between attributes.
Factors other than the structure of the category, such as frequency, were con-
trolled. After learning was completed, reaction time in a category membership
verification task proved to be a function of structural prototypicality.

Speed of Learning of Artificial Categories (Errors) and Order of Development in
Children
Rate of learning of new material and the naturally obtainable measure of
learning (combined with maturation) reflected in developmental order are two
of the most pervasive dependent variables in psychological research. In the ar-
tificial categories used by Rosch et al. (1976b), prototypicality for all three types
of stimulus material predicted speed of learning of the categories. Develop-
mentally, Anglin (1976) obtained evidence that young children learn category
membership of good examples of categories before that of poor examples. Us-
ing a category-membership verification technique, Rosch (1973) found that the
differences in reaction time to verify good and poor members were far more
extreme for 10-year-old children than for adults, indicating that the children
had learned the category membership of the prototypical members earlier than
that of other members.

Order and Probability of Item Output
Item output is normally taken to reflect some aspect of storage, retrieval, or
category search. Battig and Montague (1969) provided a normative study of
the probability with which college students listed instances of superordinate