Prototype and Exemplar Theories of Concepts
(This page last updated 30 March 2009.)
We will explore four ways of representing concepts. This page
will describe two methods, and the remaining two are described on the
pages before and after this one.
- Single exemplar selected as prototype
- May be real exemplar, or combination of features from
- Membership in category determined by similarity to
- Higher similarity = better member of category
- A category defined by a prototype will have graded membership
and a fuzzy boundary.
- Some items will be very similar to the prototype, and will
clearly be a member.
- Other items will be less similar to the prototype, but may
still be similar enough to be classified as a member.
- Allows for categories with family resemblance structure.
Experiments that Support the Idea that Concepts are Represented
- Typicality Ratings
- Picture Identification
- Sentence Verification
- Induction of Unfamiliar Properties
- Making Up Sentences
See the description of these experiments in the
- Results from all of these different types of experiments
support the same sort of category structure.
- The category members that get the highest typicality ratings
and that are named first also produce the fastest sentence
verification , etc.
- Rather than relying on a single prototype, we can also
represent a category by storing many or all known exemplars of the
- When a new item is encountered, it is compared against all the
- Of course, this increases the memory requirement.
- Exemplar theories of concepts can also explain graded
- The more exemplars that a stimulus matches, the better it
fits into a category.
- The experimental results that support prototypes can generally
be explained by exemplar theories.
One Advantage of Exemplar Models over Prototype Models
- Exemplar models can preserve information about the correlation
of different features within a category.
- Medin et. al. (1982) showed that subjects do use information
about correlated features.
- Their subjects first studied a set of examples to learn a
category. Then they had to decide whether new instances
belonged in the category or not.
- After learning the category of patients with burlosis,
subjects receive pairs of new patients and must decide which is
more likely to have burlosis.
- Both patients have the same number of symptoms, but in the
first patient, the last two symptoms are correlated, while in
the second patient they are not. None of the earlier patients
had a pattern like the second patient.
- Subjects were more likely to pick the first patient.
- See description of Medin et. al. in textbook for more
- Some evidence suggests that prototypes are more likely to be
used than exemplars after long experience with a concept.
next class: Concepts as
Psych 315H: Cognitive